// SPDX-License-Identifier: GPL-2.0
/*
 * Performance events core code:
 *
 *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
 *  Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
 *  Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra
 *  Copyright  ©  2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
 */

#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/idr.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/hash.h>
#include <linux/tick.h>
#include <linux/sysfs.h>
#include <linux/dcache.h>
#include <linux/percpu.h>
#include <linux/ptrace.h>
#include <linux/reboot.h>
#include <linux/vmstat.h>
#include <linux/device.h>
#include <linux/export.h>
#include <linux/vmalloc.h>
#include <linux/hardirq.h>
#include <linux/hugetlb.h>
#include <linux/rculist.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/anon_inodes.h>
#include <linux/kernel_stat.h>
#include <linux/cgroup.h>
#include <linux/perf_event.h>
#include <linux/trace_events.h>
#include <linux/hw_breakpoint.h>
#include <linux/mm_types.h>
#include <linux/module.h>
#include <linux/mman.h>
#include <linux/compat.h>
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/namei.h>
#include <linux/parser.h>
#include <linux/sched/clock.h>
#include <linux/sched/mm.h>
#include <linux/proc_ns.h>
#include <linux/mount.h>
#include <linux/min_heap.h>

#include "internal.h"

#include <asm/irq_regs.h>

typedef int (*remote_function_f)(void *);

struct remote_function_call {
        struct task_struct      *p;
        remote_function_f       func;
        void                    *info;
        int                     ret;
};

static void remote_function(void *data)
{
        struct remote_function_call *tfc = data;
        struct task_struct *p = tfc->p;

        if (p) {
                /* -EAGAIN */
                if (task_cpu(p) != smp_processor_id())
                        return;

                /*
                 * Now that we're on right CPU with IRQs disabled, we can test
                 * if we hit the right task without races.
                 */

                tfc->ret = -ESRCH; /* No such (running) process */
                if (p != current)
                        return;
        }

        tfc->ret = tfc->func(tfc->info);
}

/**
 * task_function_call - call a function on the cpu on which a task runs
 * @p:          the task to evaluate
 * @func:       the function to be called
 * @info:       the function call argument
 *
 * Calls the function @func when the task is currently running. This might
 * be on the current CPU, which just calls the function directly.  This will
 * retry due to any failures in smp_call_function_single(), such as if the
 * task_cpu() goes offline concurrently.
 *
 * returns @func return value or -ESRCH or -ENXIO when the process isn't running
 */
static int
task_function_call(struct task_struct *p, remote_function_f func, void *info)
{
        struct remote_function_call data = {
                .p      = p,
                .func   = func,
                .info   = info,
                .ret    = -EAGAIN,
        };
        int ret;

        for (;;) {
                ret = smp_call_function_single(task_cpu(p), remote_function,
                                               &data, 1);
                if (!ret)
                        ret = data.ret;

                if (ret != -EAGAIN)
                        break;

                cond_resched();
        }

        return ret;
}

/**
 * cpu_function_call - call a function on the cpu
 * @func:       the function to be called
 * @info:       the function call argument
 *
 * Calls the function @func on the remote cpu.
 *
 * returns: @func return value or -ENXIO when the cpu is offline
 */
static int cpu_function_call(int cpu, remote_function_f func, void *info)
{
        struct remote_function_call data = {
                .p      = NULL,
                .func   = func,
                .info   = info,
                .ret    = -ENXIO, /* No such CPU */
        };

        smp_call_function_single(cpu, remote_function, &data, 1);

        return data.ret;
}

static inline struct perf_cpu_context *
__get_cpu_context(struct perf_event_context *ctx)
{
        return this_cpu_ptr(ctx->pmu->pmu_cpu_context);
}

static void perf_ctx_lock(struct perf_cpu_context *cpuctx,
                          struct perf_event_context *ctx)
{
        raw_spin_lock(&cpuctx->ctx.lock);
        if (ctx)
                raw_spin_lock(&ctx->lock);
}

static void perf_ctx_unlock(struct perf_cpu_context *cpuctx,
                            struct perf_event_context *ctx)
{
        if (ctx)
                raw_spin_unlock(&ctx->lock);
        raw_spin_unlock(&cpuctx->ctx.lock);
}

#define TASK_TOMBSTONE ((void *)-1L)

static bool is_kernel_event(struct perf_event *event)
{
        return READ_ONCE(event->owner) == TASK_TOMBSTONE;
}

/*
 * On task ctx scheduling...
 *
 * When !ctx->nr_events a task context will not be scheduled. This means
 * we can disable the scheduler hooks (for performance) without leaving
 * pending task ctx state.
 *
 * This however results in two special cases:
 *
 *  - removing the last event from a task ctx; this is relatively straight
 *    forward and is done in __perf_remove_from_context.
 *
 *  - adding the first event to a task ctx; this is tricky because we cannot
 *    rely on ctx->is_active and therefore cannot use event_function_call().
 *    See perf_install_in_context().
 *
 * If ctx->nr_events, then ctx->is_active and cpuctx->task_ctx are set.
 */

typedef void (*event_f)(struct perf_event *, struct perf_cpu_context *,
                        struct perf_event_context *, void *);

struct event_function_struct {
        struct perf_event *event;
        event_f func;
        void *data;
};

static int event_function(void *info)
{
        struct event_function_struct *efs = info;
        struct perf_event *event = efs->event;
        struct perf_event_context *ctx = event->ctx;
        struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
        struct perf_event_context *task_ctx = cpuctx->task_ctx;
        int ret = 0;

        lockdep_assert_irqs_disabled();

        perf_ctx_lock(cpuctx, task_ctx);
        /*
         * Since we do the IPI call without holding ctx->lock things can have
         * changed, double check we hit the task we set out to hit.
         */
        if (ctx->task) {
                if (ctx->task != current) {
                        ret = -ESRCH;
                        goto unlock;
                }

                /*
                 * We only use event_function_call() on established contexts,
                 * and event_function() is only ever called when active (or
                 * rather, we'll have bailed in task_function_call() or the
                 * above ctx->task != current test), therefore we must have
                 * ctx->is_active here.
                 */
                WARN_ON_ONCE(!ctx->is_active);
                /*
                 * And since we have ctx->is_active, cpuctx->task_ctx must
                 * match.
                 */
                WARN_ON_ONCE(task_ctx != ctx);
        } else {
                WARN_ON_ONCE(&cpuctx->ctx != ctx);
        }

        efs->func(event, cpuctx, ctx, efs->data);
unlock:
        perf_ctx_unlock(cpuctx, task_ctx);

        return ret;
}

static void event_function_call(struct perf_event *event, event_f func, void *data)
{
        struct perf_event_context *ctx = event->ctx;
        struct task_struct *task = READ_ONCE(ctx->task); /* verified in event_function */
        struct event_function_struct efs = {
                .event = event,
                .func = func,
                .data = data,
        };

        if (!event->parent) {
                /*
                 * If this is a !child event, we must hold ctx::mutex to
                 * stabilize the the event->ctx relation. See
                 * perf_event_ctx_lock().
                 */
                lockdep_assert_held(&ctx->mutex);
        }

        if (!task) {
                cpu_function_call(event->cpu, event_function, &efs);
                return;
        }

        if (task == TASK_TOMBSTONE)
                return;

again:
        if (!task_function_call(task, event_function, &efs))
                return;

        raw_spin_lock_irq(&ctx->lock);
        /*
         * Reload the task pointer, it might have been changed by
         * a concurrent perf_event_context_sched_out().
         */
        task = ctx->task;
        if (task == TASK_TOMBSTONE) {
                raw_spin_unlock_irq(&ctx->lock);
                return;
        }
        if (ctx->is_active) {
                raw_spin_unlock_irq(&ctx->lock);
                goto again;
        }
        func(event, NULL, ctx, data);
        raw_spin_unlock_irq(&ctx->lock);
}

/*
 * Similar to event_function_call() + event_function(), but hard assumes IRQs
 * are already disabled and we're on the right CPU.
 */
static void event_function_local(struct perf_event *event, event_f func, void *data)
{
        struct perf_event_context *ctx = event->ctx;
        struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
        struct task_struct *task = READ_ONCE(ctx->task);
        struct perf_event_context *task_ctx = NULL;

        lockdep_assert_irqs_disabled();

        if (task) {
                if (task == TASK_TOMBSTONE)
                        return;

                task_ctx = ctx;
        }

        perf_ctx_lock(cpuctx, task_ctx);

        task = ctx->task;
        if (task == TASK_TOMBSTONE)
                goto unlock;

        if (task) {
                /*
                 * We must be either inactive or active and the right task,
                 * otherwise we're screwed, since we cannot IPI to somewhere
                 * else.
                 */
                if (ctx->is_active) {
                        if (WARN_ON_ONCE(task != current))
                                goto unlock;

                        if (WARN_ON_ONCE(cpuctx->task_ctx != ctx))
                                goto unlock;
                }
        } else {
                WARN_ON_ONCE(&cpuctx->ctx != ctx);
        }

        func(event, cpuctx, ctx, data);
unlock:
        perf_ctx_unlock(cpuctx, task_ctx);
}

#define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\
                       PERF_FLAG_FD_OUTPUT  |\
                       PERF_FLAG_PID_CGROUP |\
                       PERF_FLAG_FD_CLOEXEC)

/*
 * branch priv levels that need permission checks
 */
#define PERF_SAMPLE_BRANCH_PERM_PLM \
        (PERF_SAMPLE_BRANCH_KERNEL |\
         PERF_SAMPLE_BRANCH_HV)

enum event_type_t {
        EVENT_FLEXIBLE = 0x1,
        EVENT_PINNED = 0x2,
        EVENT_TIME = 0x4,
        /* see ctx_resched() for details */
        EVENT_CPU = 0x8,
        EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
};

/*
 * perf_sched_events : >0 events exist
 * perf_cgroup_events: >0 per-cpu cgroup events exist on this cpu
 */

static void perf_sched_delayed(struct work_struct *work);
DEFINE_STATIC_KEY_FALSE(perf_sched_events);
static DECLARE_DELAYED_WORK(perf_sched_work, perf_sched_delayed);
static DEFINE_MUTEX(perf_sched_mutex);
static atomic_t perf_sched_count;

static DEFINE_PER_CPU(atomic_t, perf_cgroup_events);
static DEFINE_PER_CPU(struct pmu_event_list, pmu_sb_events);

static atomic_t nr_mmap_events __read_mostly;
static atomic_t nr_comm_events __read_mostly;
static atomic_t nr_namespaces_events __read_mostly;
static atomic_t nr_task_events __read_mostly;
static atomic_t nr_freq_events __read_mostly;
static atomic_t nr_switch_events __read_mostly;
static atomic_t nr_ksymbol_events __read_mostly;
static atomic_t nr_bpf_events __read_mostly;
static atomic_t nr_cgroup_events __read_mostly;
static atomic_t nr_text_poke_events __read_mostly;

static LIST_HEAD(pmus);
static DEFINE_MUTEX(pmus_lock);
static struct srcu_struct pmus_srcu;
static cpumask_var_t perf_online_mask;

/*
 * perf event paranoia level:
 *  -1 - not paranoid at all
 *   0 - disallow raw tracepoint access for unpriv
 *   1 - disallow cpu events for unpriv
 *   2 - disallow kernel profiling for unpriv
 */
int sysctl_perf_event_paranoid __read_mostly = 2;

/* Minimum for 512 kiB + 1 user control page */
int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */

/*
 * max perf event sample rate
 */
#define DEFAULT_MAX_SAMPLE_RATE         100000
#define DEFAULT_SAMPLE_PERIOD_NS        (NSEC_PER_SEC / DEFAULT_MAX_SAMPLE_RATE)
#define DEFAULT_CPU_TIME_MAX_PERCENT    25

int sysctl_perf_event_sample_rate __read_mostly = DEFAULT_MAX_SAMPLE_RATE;

static int max_samples_per_tick __read_mostly   = DIV_ROUND_UP(DEFAULT_MAX_SAMPLE_RATE, HZ);
static int perf_sample_period_ns __read_mostly  = DEFAULT_SAMPLE_PERIOD_NS;

static int perf_sample_allowed_ns __read_mostly =
        DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100;

static void update_perf_cpu_limits(void)
{
        u64 tmp = perf_sample_period_ns;

        tmp *= sysctl_perf_cpu_time_max_percent;
        tmp = div_u64(tmp, 100);
        if (!tmp)
                tmp = 1;

        WRITE_ONCE(perf_sample_allowed_ns, tmp);
}

static bool perf_rotate_context(struct perf_cpu_context *cpuctx);

int perf_proc_update_handler(struct ctl_table *table, int write,
                void *buffer, size_t *lenp, loff_t *ppos)
{
        int ret;
        int perf_cpu = sysctl_perf_cpu_time_max_percent;
        /*
         * If throttling is disabled don't allow the write:
         */
        if (write && (perf_cpu == 100 || perf_cpu == 0))
                return -EINVAL;

        ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
        if (ret || !write)
                return ret;

        max_samples_per_tick = DIV_ROUND_UP(sysctl_perf_event_sample_rate, HZ);
        perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;
        update_perf_cpu_limits();

        return 0;
}

int sysctl_perf_cpu_time_max_percent __read_mostly = DEFAULT_CPU_TIME_MAX_PERCENT;

int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
                void *buffer, size_t *lenp, loff_t *ppos)
{
        int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);

        if (ret || !write)
                return ret;

        if (sysctl_perf_cpu_time_max_percent == 100 ||
            sysctl_perf_cpu_time_max_percent == 0) {
                printk(KERN_WARNING
                       "perf: Dynamic interrupt throttling disabled, can hang your system!\n");
                WRITE_ONCE(perf_sample_allowed_ns, 0);
        } else {
                update_perf_cpu_limits();
        }

        return 0;
}

/*
 * perf samples are done in some very critical code paths (NMIs).
 * If they take too much CPU time, the system can lock up and not
 * get any real work done.  This will drop the sample rate when
 * we detect that events are taking too long.
 */
#define NR_ACCUMULATED_SAMPLES 128
static DEFINE_PER_CPU(u64, running_sample_length);

static u64 __report_avg;
static u64 __report_allowed;

static void perf_duration_warn(struct irq_work *w)
{
        printk_ratelimited(KERN_INFO
                "perf: interrupt took too long (%lld > %lld), lowering "
                "kernel.perf_event_max_sample_rate to %d\n",
                __report_avg, __report_allowed,
                sysctl_perf_event_sample_rate);
}

static DEFINE_IRQ_WORK(perf_duration_work, perf_duration_warn);

void perf_sample_event_took(u64 sample_len_ns)
{
        u64 max_len = READ_ONCE(perf_sample_allowed_ns);
        u64 running_len;
        u64 avg_len;
        u32 max;

        if (max_len == 0)
                return;

        /* Decay the counter by 1 average sample. */
        running_len = __this_cpu_read(running_sample_length);
        running_len -= running_len/NR_ACCUMULATED_SAMPLES;
        running_len += sample_len_ns;
        __this_cpu_write(running_sample_length, running_len);

        /*
         * Note: this will be biased artifically low until we have
         * seen NR_ACCUMULATED_SAMPLES. Doing it this way keeps us
         * from having to maintain a count.
         */
        avg_len = running_len/NR_ACCUMULATED_SAMPLES;
        if (avg_len <= max_len)
                return;

        __report_avg = avg_len;
        __report_allowed = max_len;

        /*
         * Compute a throttle threshold 25% below the current duration.
         */
        avg_len += avg_len / 4;
        max = (TICK_NSEC / 100) * sysctl_perf_cpu_time_max_percent;
        if (avg_len < max)
                max /= (u32)avg_len;
        else
                max = 1;

        WRITE_ONCE(perf_sample_allowed_ns, avg_len);
        WRITE_ONCE(max_samples_per_tick, max);

        sysctl_perf_event_sample_rate = max * HZ;
        perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;

        if (!irq_work_queue(&perf_duration_work)) {
                early_printk("perf: interrupt took too long (%lld > %lld), lowering "
                             "kernel.perf_event_max_sample_rate to %d\n",
                             __report_avg, __report_allowed,
                             sysctl_perf_event_sample_rate);
        }
}

static atomic64_t perf_event_id;

static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
                              enum event_type_t event_type);

static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
                             enum event_type_t event_type,
                             struct task_struct *task);

static void update_context_time(struct perf_event_context *ctx);
static u64 perf_event_time(struct perf_event *event);

void __weak perf_event_print_debug(void)        { }

extern __weak const char *perf_pmu_name(void)
{
        return "pmu";
}

static inline u64 perf_clock(void)
{
        return local_clock();
}

static inline u64 perf_event_clock(struct perf_event *event)
{
        return event->clock();
}

/*
 * State based event timekeeping...
 *
 * The basic idea is to use event->state to determine which (if any) time
 * fields to increment with the current delta. This means we only need to
 * update timestamps when we change state or when they are explicitly requested
 * (read).
 *
 * Event groups make things a little more complicated, but not terribly so. The
 * rules for a group are that if the group leader is OFF the entire group is
 * OFF, irrespecive of what the group member states are. This results in
 * __perf_effective_state().
 *
 * A futher ramification is that when a group leader flips between OFF and
 * !OFF, we need to update all group member times.
 *
 *
 * NOTE: perf_event_time() is based on the (cgroup) context time, and thus we
 * need to make sure the relevant context time is updated before we try and
 * update our timestamps.
 */

static __always_inline enum perf_event_state
__perf_effective_state(struct perf_event *event)
{
        struct perf_event *leader = event->group_leader;

        if (leader->state <= PERF_EVENT_STATE_OFF)
                return leader->state;

        return event->state;
}

static __always_inline void
__perf_update_times(struct perf_event *event, u64 now, u64 *enabled, u64 *running)
{
        enum perf_event_state state = __perf_effective_state(event);
        u64 delta = now - event->tstamp;

        *enabled = event->total_time_enabled;
        if (state >= PERF_EVENT_STATE_INACTIVE)
                *enabled += delta;

        *running = event->total_time_running;
        if (state >= PERF_EVENT_STATE_ACTIVE)
                *running += delta;
}

static void perf_event_update_time(struct perf_event *event)
{
        u64 now = perf_event_time(event);

        __perf_update_times(event, now, &event->total_time_enabled,
                                        &event->total_time_running);
        event->tstamp = now;
}

static void perf_event_update_sibling_time(struct perf_event *leader)
{
        struct perf_event *sibling;

        for_each_sibling_event(sibling, leader)
                perf_event_update_time(sibling);
}

static void
perf_event_set_state(struct perf_event *event, enum perf_event_state state)
{
        if (event->state == state)
                return;

        perf_event_update_time(event);
        /*
         * If a group leader gets enabled/disabled all its siblings
         * are affected too.
         */
        if ((event->state < 0) ^ (state < 0))
                perf_event_update_sibling_time(event);

        WRITE_ONCE(event->state, state);
}

#ifdef CONFIG_CGROUP_PERF

static inline bool
perf_cgroup_match(struct perf_event *event)
{
        struct perf_event_context *ctx = event->ctx;
        struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

        /* @event doesn't care about cgroup */
        if (!event->cgrp)
                return true;

        /* wants specific cgroup scope but @cpuctx isn't associated with any */
        if (!cpuctx->cgrp)
                return false;

        /*
         * Cgroup scoping is recursive.  An event enabled for a cgroup is
         * also enabled for all its descendant cgroups.  If @cpuctx's
         * cgroup is a descendant of @event's (the test covers identity
         * case), it's a match.
         */
        return cgroup_is_descendant(cpuctx->cgrp->css.cgroup,
                                    event->cgrp->css.cgroup);
}

static inline void perf_detach_cgroup(struct perf_event *event)
{
        css_put(&event->cgrp->css);
        event->cgrp = NULL;
}

static inline int is_cgroup_event(struct perf_event *event)
{
        return event->cgrp != NULL;
}

static inline u64 perf_cgroup_event_time(struct perf_event *event)
{
        struct perf_cgroup_info *t;

        t = per_cpu_ptr(event->cgrp->info, event->cpu);
        return t->time;
}

static inline void __update_cgrp_time(struct perf_cgroup *cgrp)
{
        struct perf_cgroup_info *info;
        u64 now;

        now = perf_clock();

        info = this_cpu_ptr(cgrp->info);

        info->time += now - info->timestamp;
        info->timestamp = now;
}

static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx)
{
        struct perf_cgroup *cgrp = cpuctx->cgrp;
        struct cgroup_subsys_state *css;

        if (cgrp) {
                for (css = &cgrp->css; css; css = css->parent) {
                        cgrp = container_of(css, struct perf_cgroup, css);
                        __update_cgrp_time(cgrp);
                }
        }
}

static inline void update_cgrp_time_from_event(struct perf_event *event)
{
        struct perf_cgroup *cgrp;

        /*
         * ensure we access cgroup data only when needed and
         * when we know the cgroup is pinned (css_get)
         */
        if (!is_cgroup_event(event))
                return;

        cgrp = perf_cgroup_from_task(current, event->ctx);
        /*
         * Do not update time when cgroup is not active
         */
        if (cgroup_is_descendant(cgrp->css.cgroup, event->cgrp->css.cgroup))
                __update_cgrp_time(event->cgrp);
}

static inline void
perf_cgroup_set_timestamp(struct task_struct *task,
                          struct perf_event_context *ctx)
{
        struct perf_cgroup *cgrp;
        struct perf_cgroup_info *info;
        struct cgroup_subsys_state *css;

        /*
         * ctx->lock held by caller
         * ensure we do not access cgroup data
         * unless we have the cgroup pinned (css_get)
         */
        if (!task || !ctx->nr_cgroups)
                return;

        cgrp = perf_cgroup_from_task(task, ctx);

        for (css = &cgrp->css; css; css = css->parent) {
                cgrp = container_of(css, struct perf_cgroup, css);
                info = this_cpu_ptr(cgrp->info);
                info->timestamp = ctx->timestamp;
        }
}

static DEFINE_PER_CPU(struct list_head, cgrp_cpuctx_list);

#define PERF_CGROUP_SWOUT       0x1 /* cgroup switch out every event */
#define PERF_CGROUP_SWIN        0x2 /* cgroup switch in events based on task */

/*
 * reschedule events based on the cgroup constraint of task.
 *
 * mode SWOUT : schedule out everything
 * mode SWIN : schedule in based on cgroup for next
 */
static void perf_cgroup_switch(struct task_struct *task, int mode)
{
        struct perf_cpu_context *cpuctx;
        struct list_head *list;
        unsigned long flags;

        /*
         * Disable interrupts and preemption to avoid this CPU's
         * cgrp_cpuctx_entry to change under us.
         */
        local_irq_save(flags);

        list = this_cpu_ptr(&cgrp_cpuctx_list);
        list_for_each_entry(cpuctx, list, cgrp_cpuctx_entry) {
                WARN_ON_ONCE(cpuctx->ctx.nr_cgroups == 0);

                perf_ctx_lock(cpuctx, cpuctx->task_ctx);
                perf_pmu_disable(cpuctx->ctx.pmu);

                if (mode & PERF_CGROUP_SWOUT) {
                        cpu_ctx_sched_out(cpuctx, EVENT_ALL);
                        /*
                         * must not be done before ctxswout due
                         * to event_filter_match() in event_sched_out()
                         */
                        cpuctx->cgrp = NULL;
                }

                if (mode & PERF_CGROUP_SWIN) {
                        WARN_ON_ONCE(cpuctx->cgrp);
                        /*
                         * set cgrp before ctxsw in to allow
                         * event_filter_match() to not have to pass
                         * task around
                         * we pass the cpuctx->ctx to perf_cgroup_from_task()
                         * because cgorup events are only per-cpu
                         */
                        cpuctx->cgrp = perf_cgroup_from_task(task,
                                                             &cpuctx->ctx);
                        cpu_ctx_sched_in(cpuctx, EVENT_ALL, task);
                }
                perf_pmu_enable(cpuctx->ctx.pmu);
                perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
        }

        local_irq_restore(flags);
}

static inline void perf_cgroup_sched_out(struct task_struct *task,
                                         struct task_struct *next)
{
        struct perf_cgroup *cgrp1;
        struct perf_cgroup *cgrp2 = NULL;

        rcu_read_lock();
        /*
         * we come here when we know perf_cgroup_events > 0
         * we do not need to pass the ctx here because we know
         * we are holding the rcu lock
         */
        cgrp1 = perf_cgroup_from_task(task, NULL);
        cgrp2 = perf_cgroup_from_task(next, NULL);

        /*
         * only schedule out current cgroup events if we know
         * that we are switching to a different cgroup. Otherwise,
         * do no touch the cgroup events.
         */
        if (cgrp1 != cgrp2)
                perf_cgroup_switch(task, PERF_CGROUP_SWOUT);

        rcu_read_unlock();
}

static inline void perf_cgroup_sched_in(struct task_struct *prev,
                                        struct task_struct *task)
{
        struct perf_cgroup *cgrp1;
        struct perf_cgroup *cgrp2 = NULL;

        rcu_read_lock();
        /*
         * we come here when we know perf_cgroup_events > 0
         * we do not need to pass the ctx here because we know
         * we are holding the rcu lock
         */
        cgrp1 = perf_cgroup_from_task(task, NULL);
        cgrp2 = perf_cgroup_from_task(prev, NULL);

        /*
         * only need to schedule in cgroup events if we are changing
         * cgroup during ctxsw. Cgroup events were not scheduled
         * out of ctxsw out if that was not the case.
         */
        if (cgrp1 != cgrp2)
                perf_cgroup_switch(task, PERF_CGROUP_SWIN);

        rcu_read_unlock();
}

static int perf_cgroup_ensure_storage(struct perf_event *event,
                                struct cgroup_subsys_state *css)
{
        struct perf_cpu_context *cpuctx;
        struct perf_event **storage;
        int cpu, heap_size, ret = 0;

        /*
         * Allow storage to have sufficent space for an iterator for each
         * possibly nested cgroup plus an iterator for events with no cgroup.
         */
        for (heap_size = 1; css; css = css->parent)
                heap_size++;

        for_each_possible_cpu(cpu) {
                cpuctx = per_cpu_ptr(event->pmu->pmu_cpu_context, cpu);
                if (heap_size <= cpuctx->heap_size)
                        continue;

                storage = kmalloc_node(heap_size * sizeof(struct perf_event *),
                                       GFP_KERNEL, cpu_to_node(cpu));
                if (!storage) {
                        ret = -ENOMEM;
                        break;
                }

                raw_spin_lock_irq(&cpuctx->ctx.lock);
                if (cpuctx->heap_size < heap_size) {
                        swap(cpuctx->heap, storage);
                        if (storage == cpuctx->heap_default)
                                storage = NULL;
                        cpuctx->heap_size = heap_size;
                }
                raw_spin_unlock_irq(&cpuctx->ctx.lock);

                kfree(storage);
        }

        return ret;
}

static inline int perf_cgroup_connect(int fd, struct perf_event *event,
                                      struct perf_event_attr *attr,
                                      struct perf_event *group_leader)
{
        struct perf_cgroup *cgrp;
        struct cgroup_subsys_state *css;
        struct fd f = fdget(fd);
        int ret = 0;

        if (!f.file)
                return -EBADF;

        css = css_tryget_online_from_dir(f.file->f_path.dentry,
                                         &perf_event_cgrp_subsys);
        if (IS_ERR(css)) {
                ret = PTR_ERR(css);
                goto out;
        }

        ret = perf_cgroup_ensure_storage(event, css);
        if (ret)
                goto out;

        cgrp = container_of(css, struct perf_cgroup, css);
        event->cgrp = cgrp;

        /*
         * all events in a group must monitor
         * the same cgroup because a task belongs
         * to only one perf cgroup at a time
         */
        if (group_leader && group_leader->cgrp != cgrp) {
                perf_detach_cgroup(event);
                ret = -EINVAL;
        }
out:
        fdput(f);
        return ret;
}

static inline void
perf_cgroup_set_shadow_time(struct perf_event *event, u64 now)
{
        struct perf_cgroup_info *t;
        t = per_cpu_ptr(event->cgrp->info, event->cpu);
        event->shadow_ctx_time = now - t->timestamp;
}

static inline void
perf_cgroup_event_enable(struct perf_event *event, struct perf_event_context *ctx)
{
        struct perf_cpu_context *cpuctx;

        if (!is_cgroup_event(event))
                return;

        /*
         * Because cgroup events are always per-cpu events,
         * @ctx == &cpuctx->ctx.

         */
        cpuctx = container_of(ctx, struct perf_cpu_context, ctx);

        /*
         * Since setting cpuctx->cgrp is conditional on the current @cgrp
         * matching the event's cgroup, we must do this for every new event,
         * because if the first would mismatch, the second would not try again
         * and we would leave cpuctx->cgrp unset.
         */
        if (ctx->is_active && !cpuctx->cgrp) {
                struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx);

                if (cgroup_is_descendant(cgrp->css.cgroup, event->cgrp->css.cgroup))
                        cpuctx->cgrp = cgrp;
        }

        if (ctx->nr_cgroups++)
                return;

        list_add(&cpuctx->cgrp_cpuctx_entry,
                        per_cpu_ptr(&cgrp_cpuctx_list, event->cpu));
}

static inline void
perf_cgroup_event_disable(struct perf_event *event, struct perf_event_context *ctx)
{
        struct perf_cpu_context *cpuctx;

        if (!is_cgroup_event(event))
                return;

        /*
         * Because cgroup events are always per-cpu events,
         * @ctx == &cpuctx->ctx.
         */
        cpuctx = container_of(ctx, struct perf_cpu_context, ctx);

        if (--ctx->nr_cgroups)
                return;

        if (ctx->is_active && cpuctx->cgrp)
                cpuctx->cgrp = NULL;

        list_del(&cpuctx->cgrp_cpuctx_entry);
}

#else /* !CONFIG_CGROUP_PERF */

static inline bool
perf_cgroup_match(struct perf_event *event)
{
        return true;
}

static inline void perf_detach_cgroup(struct perf_event *event)
{}

static inline int is_cgroup_event(struct perf_event *event)
{
        return 0;
}

static inline void update_cgrp_time_from_event(struct perf_event *event)
{
}

static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx)
{
}

static inline void perf_cgroup_sched_out(struct task_struct *task,
                                         struct task_struct *next)
{
}

static inline void perf_cgroup_sched_in(struct task_struct *prev,
                                        struct task_struct *task)
{
}

static inline int perf_cgroup_connect(pid_t pid, struct perf_event *event,
                                      struct perf_event_attr *attr,
                                      struct perf_event *group_leader)
{
        return -EINVAL;
}

static inline void
perf_cgroup_set_timestamp(struct task_struct *task,
                          struct perf_event_context *ctx)
{
}

static inline void
perf_cgroup_switch(struct task_struct *task, struct task_struct *next)
{
}

static inline void
perf_cgroup_set_shadow_time(struct perf_event *event, u64 now)
{
}

static inline u64 perf_cgroup_event_time(struct perf_event *event)
{
        return 0;
}

static inline void
perf_cgroup_event_enable(struct perf_event *event, struct perf_event_context *ctx)
{
}

static inline void
perf_cgroup_event_disable(struct perf_event *event, struct perf_event_context *ctx)
{
}
#endif

/*
 * set default to be dependent on timer tick just
 * like original code
 */
#define PERF_CPU_HRTIMER (1000 / HZ)
/*
 * function must be called with interrupts disabled
 */
static enum hrtimer_restart perf_mux_hrtimer_handler(struct hrtimer *hr)
{
        struct perf_cpu_context *cpuctx;
        bool rotations;

        lockdep_assert_irqs_disabled();

        cpuctx = container_of(hr, struct perf_cpu_context, hrtimer);
        rotations = perf_rotate_context(cpuctx);

        raw_spin_lock(&cpuctx->hrtimer_lock);
        if (rotations)
                hrtimer_forward_now(hr, cpuctx->hrtimer_interval);
        else
                cpuctx->hrtimer_active = 0;
        raw_spin_unlock(&cpuctx->hrtimer_lock);

        return rotations ? HRTIMER_RESTART : HRTIMER_NORESTART;
}

static void __perf_mux_hrtimer_init(struct perf_cpu_context *cpuctx, int cpu)
{
        struct hrtimer *timer = &cpuctx->hrtimer;
        struct pmu *pmu = cpuctx->ctx.pmu;
        u64 interval;

        /* no multiplexing needed for SW PMU */
        if (pmu->task_ctx_nr == perf_sw_context)
                return;

        /*
         * check default is sane, if not set then force to
         * default interval (1/tick)
         */
        interval = pmu->hrtimer_interval_ms;
        if (interval < 1)
                interval = pmu->hrtimer_interval_ms = PERF_CPU_HRTIMER;

        cpuctx->hrtimer_interval = ns_to_ktime(NSEC_PER_MSEC * interval);

        raw_spin_lock_init(&cpuctx->hrtimer_lock);
        hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
        timer->function = perf_mux_hrtimer_handler;
}

static int perf_mux_hrtimer_restart(struct perf_cpu_context *cpuctx)
{
        struct hrtimer *timer = &cpuctx->hrtimer;
        struct pmu *pmu = cpuctx->ctx.pmu;
        unsigned long flags;

        /* not for SW PMU */
        if (pmu->task_ctx_nr == perf_sw_context)
                return 0;

        raw_spin_lock_irqsave(&cpuctx->hrtimer_lock, flags);
        if (!cpuctx->hrtimer_active) {
                cpuctx->hrtimer_active = 1;
                hrtimer_forward_now(timer, cpuctx->hrtimer_interval);
                hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED_HARD);
        }
        raw_spin_unlock_irqrestore(&cpuctx->hrtimer_lock, flags);

        return 0;
}

void perf_pmu_disable(struct pmu *pmu)
{
        int *count = this_cpu_ptr(pmu->pmu_disable_count);
        if (!(*count)++)
                pmu->pmu_disable(pmu);
}

void perf_pmu_enable(struct pmu *pmu)
{
        int *count = this_cpu_ptr(pmu->pmu_disable_count);
        if (!--(*count))
                pmu->pmu_enable(pmu);
}

static DEFINE_PER_CPU(struct list_head, active_ctx_list);

/*
 * perf_event_ctx_activate(), perf_event_ctx_deactivate(), and
 * perf_event_task_tick() are fully serialized because they're strictly cpu
 * affine and perf_event_ctx{activate,deactivate} are called with IRQs
 * disabled, while perf_event_task_tick is called from IRQ context.
 */
static void perf_event_ctx_activate(struct perf_event_context *ctx)
{
        struct list_head *head = this_cpu_ptr(&active_ctx_list);

        lockdep_assert_irqs_disabled();

        WARN_ON(!list_empty(&ctx->active_ctx_list));

        list_add(&ctx->active_ctx_list, head);
}

static void perf_event_ctx_deactivate(struct perf_event_context *ctx)
{
        lockdep_assert_irqs_disabled();

        WARN_ON(list_empty(&ctx->active_ctx_list));

        list_del_init(&ctx->active_ctx_list);
}

static void get_ctx(struct perf_event_context *ctx)
{
        refcount_inc(&ctx->refcount);
}

static void *alloc_task_ctx_data(struct pmu *pmu)
{
        if (pmu->task_ctx_cache)
                return kmem_cache_zalloc(pmu->task_ctx_cache, GFP_KERNEL);

        return NULL;
}

static void free_task_ctx_data(struct pmu *pmu, void *task_ctx_data)
{
        if (pmu->task_ctx_cache && task_ctx_data)
                kmem_cache_free(pmu->task_ctx_cache, task_ctx_data);
}

static void free_ctx(struct rcu_head *head)
{
        struct perf_event_context *ctx;

        ctx = container_of(head, struct perf_event_context, rcu_head);
        free_task_ctx_data(ctx->pmu, ctx->task_ctx_data);
        kfree(ctx);
}

static void put_ctx(struct perf_event_context *ctx)
{
        if (refcount_dec_and_test(&ctx->refcount)) {
                if (ctx->parent_ctx)
                        put_ctx(ctx->parent_ctx);
                if (ctx->task && ctx->task != TASK_TOMBSTONE)
                        put_task_struct(ctx->task);
                call_rcu(&ctx->rcu_head, free_ctx);
        }
}

/*
 * Because of perf_event::ctx migration in sys_perf_event_open::move_group and
 * perf_pmu_migrate_context() we need some magic.
 *
 * Those places that change perf_event::ctx will hold both
 * perf_event_ctx::mutex of the 'old' and 'new' ctx value.
 *
 * Lock ordering is by mutex address. There are two other sites where
 * perf_event_context::mutex nests and those are:
 *
 *  - perf_event_exit_task_context()    [ child , 0 ]
 *      perf_event_exit_event()
 *        put_event()                   [ parent, 1 ]
 *
 *  - perf_event_init_context()         [ parent, 0 ]
 *      inherit_task_group()
 *        inherit_group()
 *          inherit_event()
 *            perf_event_alloc()
 *              perf_init_event()
 *                perf_try_init_event() [ child , 1 ]
 *
 * While it appears there is an obvious deadlock here -- the parent and child
 * nesting levels are inverted between the two. This is in fact safe because
 * life-time rules separate them. That is an exiting task cannot fork, and a
 * spawning task cannot (yet) exit.
 *
 * But remember that that these are parent<->child context relations, and
 * migration does not affect children, therefore these two orderings should not
 * interact.
 *
 * The change in perf_event::ctx does not affect children (as claimed above)
 * because the sys_perf_event_open() case will install a new event and break
 * the ctx parent<->child relation, and perf_pmu_migrate_context() is only
 * concerned with cpuctx and that doesn't have children.
 *
 * The places that change perf_event::ctx will issue:
 *
 *   perf_remove_from_context();
 *   synchronize_rcu();
 *   perf_install_in_context();
 *
 * to affect the change. The remove_from_context() + synchronize_rcu() should
 * quiesce the event, after which we can install it in the new location. This
 * means that only external vectors (perf_fops, prctl) can perturb the event
 * while in transit. Therefore all such accessors should also acquire
 * perf_event_context::mutex to serialize against this.
 *
 * However; because event->ctx can change while we're waiting to acquire
 * ctx->mutex we must be careful and use the below perf_event_ctx_lock()
 * function.
 *
 * Lock order:
 *    exec_update_mutex
 *      task_struct::perf_event_mutex
 *        perf_event_context::mutex
 *          perf_event::child_mutex;
 *            perf_event_context::lock
 *          perf_event::mmap_mutex
 *          mmap_lock
 *            perf_addr_filters_head::lock
 *
 *    cpu_hotplug_lock
 *      pmus_lock
 *        cpuctx->mutex / perf_event_context::mutex
 */
static struct perf_event_context *
perf_event_ctx_lock_nested(struct perf_event *event, int nesting)
{
        struct perf_event_context *ctx;

again:
        rcu_read_lock();
        ctx = READ_ONCE(event->ctx);
        if (!refcount_inc_not_zero(&ctx->refcount)) {
                rcu_read_unlock();
                goto again;
        }
        rcu_read_unlock();

        mutex_lock_nested(&ctx->mutex, nesting);
        if (event->ctx != ctx) {
                mutex_unlock(&ctx->mutex);
                put_ctx(ctx);
                goto again;
        }

        return ctx;
}

static inline struct perf_event_context *
perf_event_ctx_lock(struct perf_event *event)
{
        return perf_event_ctx_lock_nested(event, 0);
}

static void perf_event_ctx_unlock(struct perf_event *event,
                                  struct perf_event_context *ctx)
{
        mutex_unlock(&ctx->mutex);
        put_ctx(ctx);
}

/*
 * This must be done under the ctx->lock, such as to serialize against
 * context_equiv(), therefore we cannot call put_ctx() since that might end up
 * calling scheduler related locks and ctx->lock nests inside those.
 */
static __must_check struct perf_event_context *
unclone_ctx(struct perf_event_context *ctx)
{
        struct perf_event_context *parent_ctx = ctx->parent_ctx;

        lockdep_assert_held(&ctx->lock);

        if (parent_ctx)
                ctx->parent_ctx = NULL;
        ctx->generation++;

        return parent_ctx;
}

static u32 perf_event_pid_type(struct perf_event *event, struct task_struct *p,
                                enum pid_type type)
{
        u32 nr;
        /*
         * only top level events have the pid namespace they were created in
         */
        if (event->parent)
                event = event->parent;

        nr = __task_pid_nr_ns(p, type, event->ns);
        /* avoid -1 if it is idle thread or runs in another ns */
        if (!nr && !pid_alive(p))
                nr = -1;
        return nr;
}

static u32 perf_event_pid(struct perf_event *event, struct task_struct *p)
{
        return perf_event_pid_type(event, p, PIDTYPE_TGID);
}

static u32 perf_event_tid(struct perf_event *event, struct task_struct *p)
{
        return perf_event_pid_type(event, p, PIDTYPE_PID);
}

/*
 * If we inherit events we want to return the parent event id
 * to userspace.
 */
static u64 primary_event_id(struct perf_event *event)
{
        u64 id = event->id;

        if (event->parent)
                id = event->parent->id;

        return id;
}

/*
 * Get the perf_event_context for a task and lock it.
 *
 * This has to cope with with the fact that until it is locked,
 * the context could get moved to another task.
 */
static struct perf_event_context *
perf_lock_task_context(struct task_struct *task, int ctxn, unsigned long *flags)
{
        struct perf_event_context *ctx;

retry:
        /*
         * One of the few rules of preemptible RCU is that one cannot do
         * rcu_read_unlock() while holding a scheduler (or nested) lock when
         * part of the read side critical section was irqs-enabled -- see
         * rcu_read_unlock_special().
         *
         * Since ctx->lock nests under rq->lock we must ensure the entire read
         * side critical section has interrupts disabled.
         */
        local_irq_save(*flags);
        rcu_read_lock();
        ctx = rcu_dereference(task->perf_event_ctxp[ctxn]);
        if (ctx) {
                /*
                 * If this context is a clone of another, it might
                 * get swapped for another underneath us by
                 * perf_event_task_sched_out, though the
                 * rcu_read_lock() protects us from any context
                 * getting freed.  Lock the context and check if it
                 * got swapped before we could get the lock, and retry
                 * if so.  If we locked the right context, then it
                 * can't get swapped on us any more.
                 */
                raw_spin_lock(&ctx->lock);
                if (ctx != rcu_dereference(task->perf_event_ctxp[ctxn])) {
                        raw_spin_unlock(&ctx->lock);
                        rcu_read_unlock();
                        local_irq_restore(*flags);
                        goto retry;
                }

                if (ctx->task == TASK_TOMBSTONE ||
                    !refcount_inc_not_zero(&ctx->refcount)) {
                        raw_spin_unlock(&ctx->lock);
                        ctx = NULL;
                } else {
                        WARN_ON_ONCE(ctx->task != task);
                }
        }
        rcu_read_unlock();
        if (!ctx)
                local_irq_restore(*flags);
        return ctx;
}

/*
 * Get the context for a task and increment its pin_count so it
 * can't get swapped to another task.  This also increments its
 * reference count so that the context can't get freed.
 */
static struct perf_event_context *
perf_pin_task_context(struct task_struct *task, int ctxn)
{
        struct perf_event_context *ctx;
        unsigned long flags;

        ctx = perf_lock_task_context(task, ctxn, &flags);
        if (ctx) {
                ++ctx->pin_count;
                raw_spin_unlock_irqrestore(&ctx->lock, flags);
        }
        return ctx;
}

static void perf_unpin_context(struct perf_event_context *ctx)
{
        unsigned long flags;

        raw_spin_lock_irqsave(&ctx->lock, flags);
        --ctx->pin_count;
        raw_spin_unlock_irqrestore(&ctx->lock, flags);
}

/*
 * Update the record of the current time in a context.
 */
static void update_context_time(struct perf_event_context *ctx)
{
        u64 now = perf_clock();

        ctx->time += now - ctx->timestamp;
        ctx->timestamp = now;
}

static u64 perf_event_time(struct perf_event *event)
{
        struct perf_event_context *ctx = event->ctx;

        if (is_cgroup_event(event))
                return perf_cgroup_event_time(event);

        return ctx ? ctx->time : 0;
}

static enum event_type_t get_event_type(struct perf_event *event)
{
        struct perf_event_context *ctx = event->ctx;
        enum event_type_t event_type;

        lockdep_assert_held(&ctx->lock);

        /*
         * It's 'group type', really, because if our group leader is
         * pinned, so are we.
         */
        if (event->group_leader != event)
                event = event->group_leader;

        event_type = event->attr.pinned ? EVENT_PINNED : EVENT_FLEXIBLE;
        if (!ctx->task)
                event_type |= EVENT_CPU;

        return event_type;
}

/*
 * Helper function to initialize event group nodes.
 */
static void init_event_group(struct perf_event *event)
{
        RB_CLEAR_NODE(&event->group_node);
        event->group_index = 0;
}

/*
 * Extract pinned or flexible groups from the context
 * based on event attrs bits.
 */
static struct perf_event_groups *
get_event_groups(struct perf_event *event, struct perf_event_context *ctx)
{
        if (event->attr.pinned)
                return &ctx->pinned_groups;
        else
                return &ctx->flexible_groups;
}

/*
 * Helper function to initializes perf_event_group trees.
 */
static void perf_event_groups_init(struct perf_event_groups *groups)
{
        groups->tree = RB_ROOT;
        groups->index = 0;
}

/*
 * Compare function for event groups;
 *
 * Implements complex key that first sorts by CPU and then by virtual index
 * which provides ordering when rotating groups for the same CPU.
 */
static bool
perf_event_groups_less(struct perf_event *left, struct perf_event *right)
{
        if (left->cpu < right->cpu)
                return true;
        if (left->cpu > right->cpu)
                return false;

#ifdef CONFIG_CGROUP_PERF
        if (left->cgrp != right->cgrp) {
                if (!left->cgrp || !left->cgrp->css.cgroup) {
                        /*
                         * Left has no cgroup but right does, no cgroups come
                         * first.
                         */
                        return true;
                }
                if (!right->cgrp || !right->cgrp->css.cgroup) {
                        /*
                         * Right has no cgroup but left does, no cgroups come
                         * first.
                         */
                        return false;
                }
                /* Two dissimilar cgroups, order by id. */
                if (left->cgrp->css.cgroup->kn->id < right->cgrp->css.cgroup->kn->id)
                        return true;

                return false;
        }
#endif

        if (left->group_index < right->group_index)
                return true;
        if (left->group_index > right->group_index)
                return false;

        return false;
}

/*
 * Insert @event into @groups' tree; using {@event->cpu, ++@groups->index} for
 * key (see perf_event_groups_less). This places it last inside the CPU
 * subtree.
 */
static void
perf_event_groups_insert(struct perf_event_groups *groups,
                         struct perf_event *event)
{
        struct perf_event *node_event;
        struct rb_node *parent;
        struct rb_node **node;

        event->group_index = ++groups->index;

        node = &groups->tree.rb_node;
        parent = *node;

        while (*node) {
                parent = *node;
                node_event = container_of(*node, struct perf_event, group_node);

                if (perf_event_groups_less(event, node_event))
                        node = &parent->rb_left;
                else
                        node = &parent->rb_right;
        }

        rb_link_node(&event->group_node, parent, node);
        rb_insert_color(&event->group_node, &groups->tree);
}

/*
 * Helper function to insert event into the pinned or flexible groups.
 */
static void
add_event_to_groups(struct perf_event *event, struct perf_event_context *ctx)
{
        struct perf_event_groups *groups;

        groups = get_event_groups(event, ctx);
        perf_event_groups_insert(groups, event);
}

/*
 * Delete a group from a tree.
 */
static void
perf_event_groups_delete(struct perf_event_groups *groups,
                         struct perf_event *event)
{
        WARN_ON_ONCE(RB_EMPTY_NODE(&event->group_node) ||
                     RB_EMPTY_ROOT(&groups->tree));

        rb_erase(&event->group_node, &groups->tree);
        init_event_group(event);
}

/*
 * Helper function to delete event from its groups.
 */
static void
del_event_from_groups(struct perf_event *event, struct perf_event_context *ctx)
{
        struct perf_event_groups *groups;

        groups = get_event_groups(event, ctx);
        perf_event_groups_delete(groups, event);
}

/*
 * Get the leftmost event in the cpu/cgroup subtree.
 */
static struct perf_event *
perf_event_groups_first(struct perf_event_groups *groups, int cpu,
                        struct cgroup *cgrp)
{
        struct perf_event *node_event = NULL, *match = NULL;
        struct rb_node *node = groups->tree.rb_node;
#ifdef CONFIG_CGROUP_PERF
        u64 node_cgrp_id, cgrp_id = 0;

        if (cgrp)
                cgrp_id = cgrp->kn->id;
#endif

        while (node) {
                node_event = container_of(node, struct perf_event, group_node);

                if (cpu < node_event->cpu) {
                        node = node->rb_left;
                        continue;
                }
                if (cpu > node_event->cpu) {
                        node = node->rb_right;
                        continue;
                }
#ifdef CONFIG_CGROUP_PERF
                node_cgrp_id = 0;
                if (node_event->cgrp && node_event->cgrp->css.cgroup)
                        node_cgrp_id = node_event->cgrp->css.cgroup->kn->id;

                if (cgrp_id < node_cgrp_id) {
                        node = node->rb_left;
                        continue;
                }
                if (cgrp_id > node_cgrp_id) {
                        node = node->rb_right;
                        continue;
                }
#endif
                match = node_event;
                node = node->rb_left;
        }

        return match;
}

/*
 * Like rb_entry_next_safe() for the @cpu subtree.
 */
static struct perf_event *
perf_event_groups_next(struct perf_event *event)
{
        struct perf_event *next;
#ifdef CONFIG_CGROUP_PERF
        u64 curr_cgrp_id = 0;
        u64 next_cgrp_id = 0;
#endif

        next = rb_entry_safe(rb_next(&event->group_node), typeof(*event), group_node);
        if (next == NULL || next->cpu != event->cpu)
                return NULL;

#ifdef CONFIG_CGROUP_PERF
        if (event->cgrp && event->cgrp->css.cgroup)
                curr_cgrp_id = event->cgrp->css.cgroup->kn->id;

        if (next->cgrp && next->cgrp->css.cgroup)
                next_cgrp_id = next->cgrp->css.cgroup->kn->id;

        if (curr_cgrp_id != next_cgrp_id)
                return NULL;
#endif
        return next;
}

/*
 * Iterate through the whole groups tree.
 */
#define perf_event_groups_for_each(event, groups)                       \
        for (event = rb_entry_safe(rb_first(&((groups)->tree)),         \
                                typeof(*event), group_node); event;     \
                event = rb_entry_safe(rb_next(&event->group_node),      \
                                typeof(*event), group_node))

/*
 * Add an event from the lists for its context.
 * Must be called with ctx->mutex and ctx->lock held.
 */
static void
list_add_event(struct perf_event *event, struct perf_event_context *ctx)
{
        lockdep_assert_held(&ctx->lock);

        WARN_ON_ONCE(event->attach_state & PERF_ATTACH_CONTEXT);
        event->attach_state |= PERF_ATTACH_CONTEXT;

        event->tstamp = perf_event_time(event);

        /*
         * If we're a stand alone event or group leader, we go to the context
         * list, group events are kept attached to the group so that
         * perf_group_detach can, at all times, locate all siblings.
         */
        if (event->group_leader == event) {
                event->group_caps = event->event_caps;
                add_event_to_groups(event, ctx);
        }

        list_add_rcu(&event->event_entry, &ctx->event_list);
        ctx->nr_events++;
        if (event->attr.inherit_stat)
                ctx->nr_stat++;

        if (event->state > PERF_EVENT_STATE_OFF)
                perf_cgroup_event_enable(event, ctx);

        ctx->generation++;
}

/*
 * Initialize event state based on the perf_event_attr::disabled.
 */
static inline void perf_event__state_init(struct perf_event *event)
{
        event->state = event->attr.disabled ? PERF_EVENT_STATE_OFF :
                                              PERF_EVENT_STATE_INACTIVE;
}

static void __perf_event_read_size(struct perf_event *event, int nr_siblings)
{
        int entry = sizeof(u64); /* value */
        int size = 0;
        int nr = 1;

        if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
                size += sizeof(u64);

        if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
                size += sizeof(u64);

        if (event->attr.read_format & PERF_FORMAT_ID)
                entry += sizeof(u64);

        if (event->attr.read_format & PERF_FORMAT_GROUP) {
                nr += nr_siblings;
                size += sizeof(u64);
        }

        size += entry * nr;
        event->read_size = size;
}

static void __perf_event_header_size(struct perf_event *event, u64 sample_type)
{
        struct perf_sample_data *data;
        u16 size = 0;

        if (sample_type & PERF_SAMPLE_IP)
                size += sizeof(data->ip);

        if (sample_type & PERF_SAMPLE_ADDR)
                size += sizeof(data->addr);

        if (sample_type & PERF_SAMPLE_PERIOD)
                size += sizeof(data->period);

        if (sample_type & PERF_SAMPLE_WEIGHT)
                size += sizeof(data->weight);

        if (sample_type & PERF_SAMPLE_READ)
                size += event->read_size;

        if (sample_type & PERF_SAMPLE_DATA_SRC)
                size += sizeof(data->data_src.val);

        if (sample_type & PERF_SAMPLE_TRANSACTION)
                size += sizeof(data->txn);

        if (sample_type & PERF_SAMPLE_PHYS_ADDR)
                size += sizeof(data->phys_addr);

        if (sample_type & PERF_SAMPLE_CGROUP)
                size += sizeof(data->cgroup);

        event->header_size = size;
}

/*
 * Called at perf_event creation and when events are attached/detached from a
 * group.
 */
static void perf_event__header_size(struct perf_event *event)
{
        __perf_event_read_size(event,
                               event->group_leader->nr_siblings);
        __perf_event_header_size(event, event->attr.sample_type);
}

static void perf_event__id_header_size(struct perf_event *event)
{
        struct perf_sample_data *data;
        u64 sample_type = event->attr.sample_type;
        u16 size = 0;

        if (sample_type & PERF_SAMPLE_TID)
                size += sizeof(data->tid_entry);

        if (sample_type & PERF_SAMPLE_TIME)
                size += sizeof(data->time);

        if (sample_type & PERF_SAMPLE_IDENTIFIER)
                size += sizeof(data->id);

        if (sample_type & PERF_SAMPLE_ID)
                size += sizeof(data->id);

        if (sample_type & PERF_SAMPLE_STREAM_ID)
                size += sizeof(data->stream_id);

        if (sample_type & PERF_SAMPLE_CPU)
                size += sizeof(data->cpu_entry);

        event->id_header_size = size;
}

static bool perf_event_validate_size(struct perf_event *event)
{
        /*
         * The values computed here will be over-written when we actually
         * attach the event.
         */
        __perf_event_read_size(event, event->group_leader->nr_siblings + 1);
        __perf_event_header_size(event, event->attr.sample_type & ~PERF_SAMPLE_READ);
        perf_event__id_header_size(event);

        /*
         * Sum the lot; should not exceed the 64k limit we have on records.
         * Conservative limit to allow for callchains and other variable fields.
         */
        if (event->read_size + event->header_size +
            event->id_header_size + sizeof(struct perf_event_header) >= 16*1024)
                return false;

        return true;
}

static void perf_group_attach(struct perf_event *event)
{
        struct perf_event *group_leader = event->group_leader, *pos;

        lockdep_assert_held(&event->ctx->lock);

        /*
         * We can have double attach due to group movement in perf_event_open.
         */
        if (event->attach_state & PERF_ATTACH_GROUP)
                return;

        event->attach_state |= PERF_ATTACH_GROUP;

        if (group_leader == event)
                return;

        WARN_ON_ONCE(group_leader->ctx != event->ctx);

        group_leader->group_caps &= event->event_caps;

        list_add_tail(&event->sibling_list, &group_leader->sibling_list);
        group_leader->nr_siblings++;

        perf_event__header_size(group_leader);

        for_each_sibling_event(pos, group_leader)
                perf_event__header_size(pos);
}

/*
 * Remove an event from the lists for its context.
 * Must be called with ctx->mutex and ctx->lock held.
 */
static void
list_del_event(struct perf_event *event, struct perf_event_context *ctx)
{
        WARN_ON_ONCE(event->ctx != ctx);
        lockdep_assert_held(&ctx->lock);

        /*

         * We can have double detach due to exit/hot-unplug + close.
         */
        if (!(event->attach_state & PERF_ATTACH_CONTEXT))
                return;

        event->attach_state &= ~PERF_ATTACH_CONTEXT;

        ctx->nr_events--;
        if (event->attr.inherit_stat)
                ctx->nr_stat--;

        list_del_rcu(&event->event_entry);

        if (event->group_leader == event)
                del_event_from_groups(event, ctx);

        /*
         * If event was in error state, then keep it
         * that way, otherwise bogus counts will be
         * returned on read(). The only way to get out
         * of error state is by explicit re-enabling
         * of the event
         */
        if (event->state > PERF_EVENT_STATE_OFF) {
                perf_cgroup_event_disable(event, ctx);
                perf_event_set_state(event, PERF_EVENT_STATE_OFF);
        }

        ctx->generation++;
}

static int
perf_aux_output_match(struct perf_event *event, struct perf_event *aux_event)
{
        if (!has_aux(aux_event))
                return 0;

        if (!event->pmu->aux_output_match)
                return 0;

        return event->pmu->aux_output_match(aux_event);
}

static void put_event(struct perf_event *event);
static void event_sched_out(struct perf_event *event,
                            struct perf_cpu_context *cpuctx,
                            struct perf_event_context *ctx);

static void perf_put_aux_event(struct perf_event *event)
{
        struct perf_event_context *ctx = event->ctx;
        struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
        struct perf_event *iter;

        /*
         * If event uses aux_event tear down the link
         */
        if (event->aux_event) {
                iter = event->aux_event;
                event->aux_event = NULL;
                put_event(iter);
                return;
        }

        /*
         * If the event is an aux_event, tear down all links to
         * it from other events.
         */
        for_each_sibling_event(iter, event->group_leader) {
                if (iter->aux_event != event)
                        continue;

                iter->aux_event = NULL;
                put_event(event);

                /*
                 * If it's ACTIVE, schedule it out and put it into ERROR
                 * state so that we don't try to schedule it again. Note
                 * that perf_event_enable() will clear the ERROR status.
                 */
                event_sched_out(iter, cpuctx, ctx);
                perf_event_set_state(event, PERF_EVENT_STATE_ERROR);
        }
}

static bool perf_need_aux_event(struct perf_event *event)
{
        return !!event->attr.aux_output || !!event->attr.aux_sample_size;
}

static int perf_get_aux_event(struct perf_event *event,
                              struct perf_event *group_leader)
{
        /*
         * Our group leader must be an aux event if we want to be
         * an aux_output. This way, the aux event will precede its
         * aux_output events in the group, and therefore will always
         * schedule first.
         */
        if (!group_leader)
                return 0;

        /*
         * aux_output and aux_sample_size are mutually exclusive.
         */
        if (event->attr.aux_output && event->attr.aux_sample_size)
                return 0;

        if (event->attr.aux_output &&
            !perf_aux_output_match(event, group_leader))
                return 0;

        if (event->attr.aux_sample_size && !group_leader->pmu->snapshot_aux)
                return 0;

        if (!atomic_long_inc_not_zero(&group_leader->refcount))
                return 0;

        /*
         * Link aux_outputs to their aux event; this is undone in
         * perf_group_detach() by perf_put_aux_event(). When the
         * group in torn down, the aux_output events loose their
         * link to the aux_event and can't schedule any more.
         */
        event->aux_event = group_leader;

        return 1;
}

static inline struct list_head *get_event_list(struct perf_event *event)
{
        struct perf_event_context *ctx = event->ctx;
        return event->attr.pinned ? &ctx->pinned_active : &ctx->flexible_active;
}

/*
 * Events that have PERF_EV_CAP_SIBLING require being part of a group and
 * cannot exist on their own, schedule them out and move them into the ERROR
 * state. Also see _perf_event_enable(), it will not be able to recover
 * this ERROR state.
 */
static inline void perf_remove_sibling_event(struct perf_event *event)
{
        struct perf_event_context *ctx = event->ctx;
        struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

        event_sched_out(event, cpuctx, ctx);
        perf_event_set_state(event, PERF_EVENT_STATE_ERROR);
}

static void perf_group_detach(struct perf_event *event)
{
        struct perf_event *leader = event->group_leader;
        struct perf_event *sibling, *tmp;
        struct perf_event_context *ctx = event->ctx;

        lockdep_assert_held(&ctx->lock);

        /*
         * We can have double detach due to exit/hot-unplug + close.
         */
        if (!(event->attach_state & PERF_ATTACH_GROUP))
                return;

        event->attach_state &= ~PERF_ATTACH_GROUP;

        perf_put_aux_event(event);

        /*
         * If this is a sibling, remove it from its group.
         */
        if (leader != event) {
                list_del_init(&event->sibling_list);
                event->group_leader->nr_siblings--;
                goto out;
        }

        /*
         * If this was a group event with sibling events then
         * upgrade the siblings to singleton events by adding them
         * to whatever list we are on.
         */
        list_for_each_entry_safe(sibling, tmp, &event->sibling_list, sibling_list) {

                if (sibling->event_caps & PERF_EV_CAP_SIBLING)
                        perf_remove_sibling_event(sibling);

                sibling->group_leader = sibling;
                list_del_init(&sibling->sibling_list);

                /* Inherit group flags from the previous leader */
                sibling->group_caps = event->group_caps;

                if (!RB_EMPTY_NODE(&event->group_node)) {
                        add_event_to_groups(sibling, event->ctx);

                        if (sibling->state == PERF_EVENT_STATE_ACTIVE)
                                list_add_tail(&sibling->active_list, get_event_list(sibling));
                }

                WARN_ON_ONCE(sibling->ctx != event->ctx);
        }

out:
        for_each_sibling_event(tmp, leader)
                perf_event__header_size(tmp);

        perf_event__header_size(leader);
}

static bool is_orphaned_event(struct perf_event *event)
{
        return event->state == PERF_EVENT_STATE_DEAD;
}

static inline int __pmu_filter_match(struct perf_event *event)
{
        struct pmu *pmu = event->pmu;
        return pmu->filter_match ? pmu->filter_match(event) : 1;
}

/*
 * Check whether we should attempt to schedule an event group based on
 * PMU-specific filtering. An event group can consist of HW and SW events,
 * potentially with a SW leader, so we must check all the filters, to
 * determine whether a group is schedulable:
 */
static inline int pmu_filter_match(struct perf_event *event)
{
        struct perf_event *sibling;

        if (!__pmu_filter_match(event))
                return 0;

        for_each_sibling_event(sibling, event) {
                if (!__pmu_filter_match(sibling))
                        return 0;
        }

        return 1;
}

static inline int
event_filter_match(struct perf_event *event)
{
        return (event->cpu == -1 || event->cpu == smp_processor_id()) &&
               perf_cgroup_match(event) && pmu_filter_match(event);
}

static void
event_sched_out(struct perf_event *event,
                  struct perf_cpu_context *cpuctx,
                  struct perf_event_context *ctx)
{
        enum perf_event_state state = PERF_EVENT_STATE_INACTIVE;

        WARN_ON_ONCE(event->ctx != ctx);
        lockdep_assert_held(&ctx->lock);

        if (event->state != PERF_EVENT_STATE_ACTIVE)
                return;

        /*
         * Asymmetry; we only schedule events _IN_ through ctx_sched_in(), but
         * we can schedule events _OUT_ individually through things like
         * __perf_remove_from_context().
         */
        list_del_init(&event->active_list);

        perf_pmu_disable(event->pmu);

        event->pmu->del(event, 0);
        event->oncpu = -1;

        if (READ_ONCE(event->pending_disable) >= 0) {
                WRITE_ONCE(event->pending_disable, -1);
                perf_cgroup_event_disable(event, ctx);
                state = PERF_EVENT_STATE_OFF;
        }
        perf_event_set_state(event, state);

        if (!is_software_event(event))
                cpuctx->active_oncpu--;
        if (!--ctx->nr_active)
                perf_event_ctx_deactivate(ctx);
        if (event->attr.freq && event->attr.sample_freq)
                ctx->nr_freq--;
        if (event->attr.exclusive || !cpuctx->active_oncpu)
                cpuctx->exclusive = 0;

        perf_pmu_enable(event->pmu);
}

static void
group_sched_out(struct perf_event *group_event,
                struct perf_cpu_context *cpuctx,
                struct perf_event_context *ctx)
{
        struct perf_event *event;

        if (group_event->state != PERF_EVENT_STATE_ACTIVE)
                return;

        perf_pmu_disable(ctx->pmu);

        event_sched_out(group_event, cpuctx, ctx);

        /*
         * Schedule out siblings (if any):
         */
        for_each_sibling_event(event, group_event)
                event_sched_out(event, cpuctx, ctx);

        perf_pmu_enable(ctx->pmu);
}

#define DETACH_GROUP    0x01UL

/*
 * Cross CPU call to remove a performance event
 *
 * We disable the event on the hardware level first. After that we
 * remove it from the context list.
 */
static void
__perf_remove_from_context(struct perf_event *event,
                           struct perf_cpu_context *cpuctx,
                           struct perf_event_context *ctx,
                           void *info)
{
        unsigned long flags = (unsigned long)info;

        if (ctx->is_active & EVENT_TIME) {
                update_context_time(ctx);
                update_cgrp_time_from_cpuctx(cpuctx);
        }

        event_sched_out(event, cpuctx, ctx);
        if (flags & DETACH_GROUP)
                perf_group_detach(event);
        list_del_event(event, ctx);

        if (!ctx->nr_events && ctx->is_active) {
                ctx->is_active = 0;
                ctx->rotate_necessary = 0;
                if (ctx->task) {
                        WARN_ON_ONCE(cpuctx->task_ctx != ctx);
                        cpuctx->task_ctx = NULL;
                }
        }
}

/*
 * Remove the event from a task's (or a CPU's) list of events.
 *
 * If event->ctx is a cloned context, callers must make sure that
 * every task struct that event->ctx->task could possibly point to
 * remains valid.  This is OK when called from perf_release since
 * that only calls us on the top-level context, which can't be a clone.
 * When called from perf_event_exit_task, it's OK because the
 * context has been detached from its task.
 */
static void perf_remove_from_context(struct perf_event *event, unsigned long flags)
{
        struct perf_event_context *ctx = event->ctx;

        lockdep_assert_held(&ctx->mutex);

        event_function_call(event, __perf_remove_from_context, (void *)flags);

        /*
         * The above event_function_call() can NO-OP when it hits
         * TASK_TOMBSTONE. In that case we must already have been detached
         * from the context (by perf_event_exit_event()) but the grouping
         * might still be in-tact.
         */
        WARN_ON_ONCE(event->attach_state & PERF_ATTACH_CONTEXT);
        if ((flags & DETACH_GROUP) &&
            (event->attach_state & PERF_ATTACH_GROUP)) {
                /*
                 * Since in that case we cannot possibly be scheduled, simply
                 * detach now.
                 */
                raw_spin_lock_irq(&ctx->lock);
                perf_group_detach(event);
                raw_spin_unlock_irq(&ctx->lock);
        }
}

/*
 * Cross CPU call to disable a performance event
 */
static void __perf_event_disable(struct perf_event *event,
                                 struct perf_cpu_context *cpuctx,
                                 struct perf_event_context *ctx,
                                 void *info)
{
        if (event->state < PERF_EVENT_STATE_INACTIVE)
                return;

        if (ctx->is_active & EVENT_TIME) {
                update_context_time(ctx);
                update_cgrp_time_from_event(event);
        }

        if (event == event->group_leader)
                group_sched_out(event, cpuctx, ctx);
        else
                event_sched_out(event, cpuctx, ctx);

        perf_event_set_state(event, PERF_EVENT_STATE_OFF);
        perf_cgroup_event_disable(event, ctx);
}

/*
 * Disable an event.
 *
 * If event->ctx is a cloned context, callers must make sure that
 * every task struct that event->ctx->task could possibly point to
 * remains valid.  This condition is satisfied when called through
 * perf_event_for_each_child or perf_event_for_each because they
 * hold the top-level event's child_mutex, so any descendant that
 * goes to exit will block in perf_event_exit_event().
 *
 * When called from perf_pending_event it's OK because event->ctx
 * is the current context on this CPU and preemption is disabled,
 * hence we can't get into perf_event_task_sched_out for this context.
 */
static void _perf_event_disable(struct perf_event *event)
{
        struct perf_event_context *ctx = event->ctx;

        raw_spin_lock_irq(&ctx->lock);
        if (event->state <= PERF_EVENT_STATE_OFF) {
                raw_spin_unlock_irq(&ctx->lock);
                return;
        }
        raw_spin_unlock_irq(&ctx->lock);

        event_function_call(event, __perf_event_disable, NULL);
}

void perf_event_disable_local(struct perf_event *event)
{
        event_function_local(event, __perf_event_disable, NULL);
}

/*
 * Strictly speaking kernel users cannot create groups and therefore this
 * interface does not need the perf_event_ctx_lock() magic.
 */
void perf_event_disable(struct perf_event *event)
{
        struct perf_event_context *ctx;

        ctx = perf_event_ctx_lock(event);
        _perf_event_disable(event);
        perf_event_ctx_unlock(event, ctx);
}
EXPORT_SYMBOL_GPL(perf_event_disable);

void perf_event_disable_inatomic(struct perf_event *event)
{
        WRITE_ONCE(event->pending_disable, smp_processor_id());
        /* can fail, see perf_pending_event_disable() */
        irq_work_queue(&event->pending);
}

static void perf_set_shadow_time(struct perf_event *event,
                                 struct perf_event_context *ctx)
{
        /*
         * use the correct time source for the time snapshot
         *
         * We could get by without this by leveraging the
         * fact that to get to this function, the caller
         * has most likely already called update_context_time()
         * and update_cgrp_time_xx() and thus both timestamp
         * are identical (or very close). Given that tstamp is,
         * already adjusted for cgroup, we could say that:
         *    tstamp - ctx->timestamp
         * is equivalent to
         *    tstamp - cgrp->timestamp.
         *
         * Then, in perf_output_read(), the calculation would
         * work with no changes because:
         * - event is guaranteed scheduled in
         * - no scheduled out in between
         * - thus the timestamp would be the same
         *
         * But this is a bit hairy.
         *
         * So instead, we have an explicit cgroup call to remain
         * within the time time source all along. We believe it
         * is cleaner and simpler to understand.
         */
        if (is_cgroup_event(event))
                perf_cgroup_set_shadow_time(event, event->tstamp);
        else
                event->shadow_ctx_time = event->tstamp - ctx->timestamp;
}

#define MAX_INTERRUPTS (~0ULL)

static void perf_log_throttle(struct perf_event *event, int enable);
static void perf_log_itrace_start(struct perf_event *event);

static int
event_sched_in(struct perf_event *event,
                 struct perf_cpu_context *cpuctx,
                 struct perf_event_context *ctx)
{
        int ret = 0;

        WARN_ON_ONCE(event->ctx != ctx);

        lockdep_assert_held(&ctx->lock);

        if (event->state <= PERF_EVENT_STATE_OFF)
                return 0;

        WRITE_ONCE(event->oncpu, smp_processor_id());
        /*
         * Order event::oncpu write to happen before the ACTIVE state is
         * visible. This allows perf_event_{stop,read}() to observe the correct
         * ->oncpu if it sees ACTIVE.
         */
        smp_wmb();
        perf_event_set_state(event, PERF_EVENT_STATE_ACTIVE);

        /*
         * Unthrottle events, since we scheduled we might have missed several
         * ticks already, also for a heavily scheduling task there is little
         * guarantee it'll get a tick in a timely manner.
         */
        if (unlikely(event->hw.interrupts == MAX_INTERRUPTS)) {
                perf_log_throttle(event, 1);
                event->hw.interrupts = 0;
        }

        perf_pmu_disable(event->pmu);

        perf_set_shadow_time(event, ctx);

        perf_log_itrace_start(event);

        if (event->pmu->add(event, PERF_EF_START)) {
                perf_event_set_state(event, PERF_EVENT_STATE_INACTIVE);
                event->oncpu = -1;
                ret = -EAGAIN;
                goto out;
        }

        if (!is_software_event(event))
                cpuctx->active_oncpu++;
        if (!ctx->nr_active++)
                perf_event_ctx_activate(ctx);
        if (event->attr.freq && event->attr.sample_freq)
                ctx->nr_freq++;

        if (event->attr.exclusive)
                cpuctx->exclusive = 1;

out:
        perf_pmu_enable(event->pmu);

        return ret;
}

static int
group_sched_in(struct perf_event *group_event,
               struct perf_cpu_context *cpuctx,
               struct perf_event_context *ctx)
{
        struct perf_event *event, *partial_group = NULL;
        struct pmu *pmu = ctx->pmu;

        if (group_event->state == PERF_EVENT_STATE_OFF)
                return 0;

        pmu->start_txn(pmu, PERF_PMU_TXN_ADD);

        if (event_sched_in(group_event, cpuctx, ctx))
                goto error;

        /*
         * Schedule in siblings as one group (if any):
         */
        for_each_sibling_event(event, group_event) {
                if (event_sched_in(event, cpuctx, ctx)) {
                        partial_group = event;
                        goto group_error;
                }
        }

        if (!pmu->commit_txn(pmu))
                return 0;

group_error:
        /*
         * Groups can be scheduled in as one unit only, so undo any
         * partial group before returning:
         * The events up to the failed event are scheduled out normally.
         */
        for_each_sibling_event(event, group_event) {
                if (event == partial_group)
                        break;

                event_sched_out(event, cpuctx, ctx);
        }
        event_sched_out(group_event, cpuctx, ctx);

error:
        pmu->cancel_txn(pmu);
        return -EAGAIN;
}

/*
 * Work out whether we can put this event group on the CPU now.
 */
static int group_can_go_on(struct perf_event *event,
                           struct perf_cpu_context *cpuctx,
                           int can_add_hw)
{
        /*
         * Groups consisting entirely of software events can always go on.
         */
        if (event->group_caps & PERF_EV_CAP_SOFTWARE)
                return 1;
        /*
         * If an exclusive group is already on, no other hardware
         * events can go on.
         */
        if (cpuctx->exclusive)
                return 0;
        /*
         * If this group is exclusive and there are already
         * events on the CPU, it can't go on.
         */
        if (event->attr.exclusive && !list_empty(get_event_list(event)))
                return 0;
        /*
         * Otherwise, try to add it if all previous groups were able
         * to go on.
         */
        return can_add_hw;
}

static void add_event_to_ctx(struct perf_event *event,
                               struct perf_event_context *ctx)
{
        list_add_event(event, ctx);
        perf_group_attach(event);
}

static void ctx_sched_out(struct perf_event_context *ctx,
                          struct perf_cpu_context *cpuctx,
                          enum event_type_t event_type);
static void
ctx_sched_in(struct perf_event_context *ctx,
             struct perf_cpu_context *cpuctx,
             enum event_type_t event_type,
             struct task_struct *task);

static void task_ctx_sched_out(struct perf_cpu_context *cpuctx,
                               struct perf_event_context *ctx,
                               enum event_type_t event_type)
{
        if (!cpuctx->task_ctx)
                return;

        if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
                return;

        ctx_sched_out(ctx, cpuctx, event_type);
}

static void perf_event_sched_in(struct perf_cpu_context *cpuctx,
                                struct perf_event_context *ctx,
                                struct task_struct *task)
{
        cpu_ctx_sched_in(cpuctx, EVENT_PINNED, task);
        if (ctx)
                ctx_sched_in(ctx, cpuctx, EVENT_PINNED, task);
        cpu_ctx_sched_in(cpuctx, EVENT_FLEXIBLE, task);
        if (ctx)
                ctx_sched_in(ctx, cpuctx, EVENT_FLEXIBLE, task);
}

/*
 * We want to maintain the following priority of scheduling:
 *  - CPU pinned (EVENT_CPU | EVENT_PINNED)
 *  - task pinned (EVENT_PINNED)
 *  - CPU flexible (EVENT_CPU | EVENT_FLEXIBLE)
 *  - task flexible (EVENT_FLEXIBLE).
 *
 * In order to avoid unscheduling and scheduling back in everything every
 * time an event is added, only do it for the groups of equal priority and
 * below.
 *
 * This can be called after a batch operation on task events, in which case
 * event_type is a bit mask of the types of events involved. For CPU events,
 * event_type is only either EVENT_PINNED or EVENT_FLEXIBLE.
 */
static void ctx_resched(struct perf_cpu_context *cpuctx,
                        struct perf_event_context *task_ctx,
                        enum event_type_t event_type)
{
        enum event_type_t ctx_event_type;
        bool cpu_event = !!(event_type & EVENT_CPU);

        /*
         * If pinned groups are involved, flexible groups also need to be
         * scheduled out.
         */
        if (event_type & EVENT_PINNED)
                event_type |= EVENT_FLEXIBLE;

        ctx_event_type = event_type & EVENT_ALL;

        perf_pmu_disable(cpuctx->ctx.pmu);
        if (task_ctx)
                task_ctx_sched_out(cpuctx, task_ctx, event_type);

        /*
         * Decide which cpu ctx groups to schedule out based on the types
         * of events that caused rescheduling:
         *  - EVENT_CPU: schedule out corresponding groups;
         *  - EVENT_PINNED task events: schedule out EVENT_FLEXIBLE groups;
         *  - otherwise, do nothing more.
         */
        if (cpu_event)
                cpu_ctx_sched_out(cpuctx, ctx_event_type);
        else if (ctx_event_type & EVENT_PINNED)
                cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);

        perf_event_sched_in(cpuctx, task_ctx, current);
        perf_pmu_enable(cpuctx->ctx.pmu);
}

void perf_pmu_resched(struct pmu *pmu)
{
        struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
        struct perf_event_context *task_ctx = cpuctx->task_ctx;

        perf_ctx_lock(cpuctx, task_ctx);
        ctx_resched(cpuctx, task_ctx, EVENT_ALL|EVENT_CPU);
        perf_ctx_unlock(cpuctx, task_ctx);
}

/*
 * Cross CPU call to install and enable a performance event
 *
 * Very similar to remote_function() + event_function() but cannot assume that
 * things like ctx->is_active and cpuctx->task_ctx are set.
 */
static int  __perf_install_in_context(void *info)
{
        struct perf_event *event = info;
        struct perf_event_context *ctx = event->ctx;
        struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
        struct perf_event_context *task_ctx = cpuctx->task_ctx;
        bool reprogram = true;
        int ret = 0;

        raw_spin_lock(&cpuctx->ctx.lock);
        if (ctx->task) {
                raw_spin_lock(&ctx->lock);
                task_ctx = ctx;

                reprogram = (ctx->task == current);

                /*
                 * If the task is running, it must be running on this CPU,
                 * otherwise we cannot reprogram things.
                 *
                 * If its not running, we don't care, ctx->lock will
                 * serialize against it becoming runnable.
                 */
                if (task_curr(ctx->task) && !reprogram) {
                        ret = -ESRCH;
                        goto unlock;
                }

                WARN_ON_ONCE(reprogram && cpuctx->task_ctx && cpuctx->task_ctx != ctx);
        } else if (task_ctx) {
                raw_spin_lock(&task_ctx->lock);
        }

#ifdef CONFIG_CGROUP_PERF
        if (event->state > PERF_EVENT_STATE_OFF && is_cgroup_event(event)) {
                /*
                 * If the current cgroup doesn't match the event's
                 * cgroup, we should not try to schedule it.
                 */
                struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx);
                reprogram = cgroup_is_descendant(cgrp->css.cgroup,
                                        event->cgrp->css.cgroup);
        }
#endif

        if (reprogram) {
                ctx_sched_out(ctx, cpuctx, EVENT_TIME);
                add_event_to_ctx(event, ctx);
                ctx_resched(cpuctx, task_ctx, get_event_type(event));
        } else {
                add_event_to_ctx(event, ctx);
        }

unlock:
        perf_ctx_unlock(cpuctx, task_ctx);

        return ret;
}

static bool exclusive_event_installable(struct perf_event *event,
                                        struct perf_event_context *ctx);

/*
 * Attach a performance event to a context.
 *
 * Very similar to event_function_call, see comment there.
 */
static void
perf_install_in_context(struct perf_event_context *ctx,
                        struct perf_event *event,
                        int cpu)
{
        struct task_struct *task = READ_ONCE(ctx->task);

        lockdep_assert_held(&ctx->mutex);

        WARN_ON_ONCE(!exclusive_event_installable(event, ctx));

        if (event->cpu != -1)
                event->cpu = cpu;

        /*
         * Ensures that if we can observe event->ctx, both the event and ctx
         * will be 'complete'. See perf_iterate_sb_cpu().
         */
        smp_store_release(&event->ctx, ctx);

        /*
         * perf_event_attr::disabled events will not run and can be initialized
         * without IPI. Except when this is the first event for the context, in
         * that case we need the magic of the IPI to set ctx->is_active.
         *
         * The IOC_ENABLE that is sure to follow the creation of a disabled
         * event will issue the IPI and reprogram the hardware.
         */
        if (__perf_effective_state(event) == PERF_EVENT_STATE_OFF && ctx->nr_events) {
                raw_spin_lock_irq(&ctx->lock);
                if (ctx->task == TASK_TOMBSTONE) {
                        raw_spin_unlock_irq(&ctx->lock);
                        return;
                }
                add_event_to_ctx(event, ctx);
                raw_spin_unlock_irq(&ctx->lock);
                return;
        }

        if (!task) {
                cpu_function_call(cpu, __perf_install_in_context, event);
                return;
        }

        /*
         * Should not happen, we validate the ctx is still alive before calling.
         */
        if (WARN_ON_ONCE(task == TASK_TOMBSTONE))
                return;

        /*
         * Installing events is tricky because we cannot rely on ctx->is_active
         * to be set in case this is the nr_events 0 -> 1 transition.
         *
         * Instead we use task_curr(), which tells us if the task is running.
         * However, since we use task_curr() outside of rq::lock, we can race
         * against the actual state. This means the result can be wrong.
         *
         * If we get a false positive, we retry, this is harmless.
         *
         * If we get a false negative, things are complicated. If we are after
         * perf_event_context_sched_in() ctx::lock will serialize us, and the
         * value must be correct. If we're before, it doesn't matter since
         * perf_event_context_sched_in() will program the counter.
         *
         * However, this hinges on the remote context switch having observed
         * our task->perf_event_ctxp[] store, such that it will in fact take
         * ctx::lock in perf_event_context_sched_in().
         *
         * We do this by task_function_call(), if the IPI fails to hit the task
         * we know any future context switch of task must see the
         * perf_event_ctpx[] store.
         */

        /*
         * This smp_mb() orders the task->perf_event_ctxp[] store with the
         * task_cpu() load, such that if the IPI then does not find the task
         * running, a future context switch of that task must observe the
         * store.
         */
        smp_mb();
again:
        if (!task_function_call(task, __perf_install_in_context, event))
                return;

        raw_spin_lock_irq(&ctx->lock);
        task = ctx->task;
        if (WARN_ON_ONCE(task == TASK_TOMBSTONE)) {
                /*
                 * Cannot happen because we already checked above (which also
                 * cannot happen), and we hold ctx->mutex, which serializes us
                 * against perf_event_exit_task_context().
                 */
                raw_spin_unlock_irq(&ctx->lock);
                return;
        }
        /*
         * If the task is not running, ctx->lock will avoid it becoming so,
         * thus we can safely install the event.
         */
        if (task_curr(task)) {
                raw_spin_unlock_irq(&ctx->lock);
                goto again;
        }
        add_event_to_ctx(event, ctx);
        raw_spin_unlock_irq(&ctx->lock);
}

/*
 * Cross CPU call to enable a performance event
 */
static void __perf_event_enable(struct perf_event *event,
                                struct perf_cpu_context *cpuctx,
                                struct perf_event_context *ctx,
                                void *info)
{
        struct perf_event *leader = event->group_leader;
        struct perf_event_context *task_ctx;

        if (event->state >= PERF_EVENT_STATE_INACTIVE ||
            event->state <= PERF_EVENT_STATE_ERROR)
                return;

        if (ctx->is_active)
                ctx_sched_out(ctx, cpuctx, EVENT_TIME);

        perf_event_set_state(event, PERF_EVENT_STATE_INACTIVE);
        perf_cgroup_event_enable(event, ctx);

        if (!ctx->is_active)
                return;

        if (!event_filter_match(event)) {
                ctx_sched_in(ctx, cpuctx, EVENT_TIME, current);
                return;
        }

        /*
         * If the event is in a group and isn't the group leader,
         * then don't put it on unless the group is on.
         */
        if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE) {
                ctx_sched_in(ctx, cpuctx, EVENT_TIME, current);
                return;
        }

        task_ctx = cpuctx->task_ctx;
        if (ctx->task)
                WARN_ON_ONCE(task_ctx != ctx);

        ctx_resched(cpuctx, task_ctx, get_event_type(event));
}

/*
 * Enable an event.
 *
 * If event->ctx is a cloned context, callers must make sure that
 * every task struct that event->ctx->task could possibly point to
 * remains valid.  This condition is satisfied when called through
 * perf_event_for_each_child or perf_event_for_each as described
 * for perf_event_disable.
 */
static void _perf_event_enable(struct perf_event *event)
{
        struct perf_event_context *ctx = event->ctx;

        raw_spin_lock_irq(&ctx->lock);
        if (event->state >= PERF_EVENT_STATE_INACTIVE ||
            event->state <  PERF_EVENT_STATE_ERROR) {
out:
                raw_spin_unlock_irq(&ctx->lock);
                return;
        }

        /*
         * If the event is in error state, clear that first.
         *

         * That way, if we see the event in error state below, we know that it
         * has gone back into error state, as distinct from the task having
         * been scheduled away before the cross-call arrived.
         */
        if (event->state == PERF_EVENT_STATE_ERROR) {
                /*
                 * Detached SIBLING events cannot leave ERROR state.
                 */
                if (event->event_caps & PERF_EV_CAP_SIBLING &&
                    event->group_leader == event)
                        goto out;

                event->state = PERF_EVENT_STATE_OFF;
        }
        raw_spin_unlock_irq(&ctx->lock);

        event_function_call(event, __perf_event_enable, NULL);
}

/*
 * See perf_event_disable();
 */
void perf_event_enable(struct perf_event *event)
{
        struct perf_event_context *ctx;

        ctx = perf_event_ctx_lock(event);
        _perf_event_enable(event);
        perf_event_ctx_unlock(event, ctx);
}
EXPORT_SYMBOL_GPL(perf_event_enable);

struct stop_event_data {
        struct perf_event       *event;
        unsigned int            restart;
};

static int __perf_event_stop(void *info)
{
        struct stop_event_data *sd = info;
        struct perf_event *event = sd->event;

        /* if it's already INACTIVE, do nothing */
        if (READ_ONCE(event->state) != PERF_EVENT_STATE_ACTIVE)
                return 0;

        /* matches smp_wmb() in event_sched_in() */
        smp_rmb();

        /*
         * There is a window with interrupts enabled before we get here,
         * so we need to check again lest we try to stop another CPU's event.
         */
        if (READ_ONCE(event->oncpu) != smp_processor_id())
                return -EAGAIN;

        event->pmu->stop(event, PERF_EF_UPDATE);

        /*
         * May race with the actual stop (through perf_pmu_output_stop()),
         * but it is only used for events with AUX ring buffer, and such
         * events will refuse to restart because of rb::aux_mmap_count==0,
         * see comments in perf_aux_output_begin().
         *
         * Since this is happening on an event-local CPU, no trace is lost
         * while restarting.
         */
        if (sd->restart)
                event->pmu->start(event, 0);

        return 0;
}

static int perf_event_stop(struct perf_event *event, int restart)
{
        struct stop_event_data sd = {
                .event          = event,
                .restart        = restart,
        };
        int ret = 0;

        do {
                if (READ_ONCE(event->state) != PERF_EVENT_STATE_ACTIVE)
                        return 0;

                /* matches smp_wmb() in event_sched_in() */
                smp_rmb();

                /*
                 * We only want to restart ACTIVE events, so if the event goes
                 * inactive here (event->oncpu==-1), there's nothing more to do;
                 * fall through with ret==-ENXIO.
                 */
                ret = cpu_function_call(READ_ONCE(event->oncpu),
                                        __perf_event_stop, &sd);
        } while (ret == -EAGAIN);

        return ret;
}

/*
 * In order to contain the amount of racy and tricky in the address filter
 * configuration management, it is a two part process:
 *
 * (p1) when userspace mappings change as a result of (1) or (2) or (3) below,
 *      we update the addresses of corresponding vmas in
 *      event::addr_filter_ranges array and bump the event::addr_filters_gen;
 * (p2) when an event is scheduled in (pmu::add), it calls
 *      perf_event_addr_filters_sync() which calls pmu::addr_filters_sync()
 *      if the generation has changed since the previous call.
 *
 * If (p1) happens while the event is active, we restart it to force (p2).
 *
 * (1) perf_addr_filters_apply(): adjusting filters' offsets based on
 *     pre-existing mappings, called once when new filters arrive via SET_FILTER
 *     ioctl;
 * (2) perf_addr_filters_adjust(): adjusting filters' offsets based on newly
 *     registered mapping, called for every new mmap(), with mm::mmap_lock down
 *     for reading;
 * (3) perf_event_addr_filters_exec(): clearing filters' offsets in the process
 *     of exec.
 */
void perf_event_addr_filters_sync(struct perf_event *event)
{
        struct perf_addr_filters_head *ifh = perf_event_addr_filters(event);

        if (!has_addr_filter(event))
                return;

        raw_spin_lock(&ifh->lock);
        if (event->addr_filters_gen != event->hw.addr_filters_gen) {
                event->pmu->addr_filters_sync(event);
                event->hw.addr_filters_gen = event->addr_filters_gen;
        }
        raw_spin_unlock(&ifh->lock);
}
EXPORT_SYMBOL_GPL(perf_event_addr_filters_sync);

static int _perf_event_refresh(struct perf_event *event, int refresh)
{
        /*
         * not supported on inherited events
         */
        if (event->attr.inherit || !is_sampling_event(event))
                return -EINVAL;

        atomic_add(refresh, &event->event_limit);
        _perf_event_enable(event);

        return 0;
}

/*
 * See perf_event_disable()
 */
int perf_event_refresh(struct perf_event *event, int refresh)
{
        struct perf_event_context *ctx;
        int ret;

        ctx = perf_event_ctx_lock(event);
        ret = _perf_event_refresh(event, refresh);
        perf_event_ctx_unlock(event, ctx);

        return ret;
}
EXPORT_SYMBOL_GPL(perf_event_refresh);

static int perf_event_modify_breakpoint(struct perf_event *bp,
                                         struct perf_event_attr *attr)
{
        int err;

        _perf_event_disable(bp);

        err = modify_user_hw_breakpoint_check(bp, attr, true);

        if (!bp->attr.disabled)
                _perf_event_enable(bp);

        return err;
}

static int perf_event_modify_attr(struct perf_event *event,
                                  struct perf_event_attr *attr)
{
        if (event->attr.type != attr->type)
                return -EINVAL;

        switch (event->attr.type) {
        case PERF_TYPE_BREAKPOINT:
                return perf_event_modify_breakpoint(event, attr);
        default:
                /* Place holder for future additions. */
                return -EOPNOTSUPP;
        }
}

static void ctx_sched_out(struct perf_event_context *ctx,
                          struct perf_cpu_context *cpuctx,
                          enum event_type_t event_type)
{
        struct perf_event *event, *tmp;
        int is_active = ctx->is_active;

        lockdep_assert_held(&ctx->lock);

        if (likely(!ctx->nr_events)) {
                /*
                 * See __perf_remove_from_context().
                 */
                WARN_ON_ONCE(ctx->is_active);
                if (ctx->task)
                        WARN_ON_ONCE(cpuctx->task_ctx);
                return;
        }

        ctx->is_active &= ~event_type;
        if (!(ctx->is_active & EVENT_ALL))
                ctx->is_active = 0;

        if (ctx->task) {
                WARN_ON_ONCE(cpuctx->task_ctx != ctx);
                if (!ctx->is_active)
                        cpuctx->task_ctx = NULL;
        }

        /*
         * Always update time if it was set; not only when it changes.
         * Otherwise we can 'forget' to update time for any but the last
         * context we sched out. For example:
         *
         *   ctx_sched_out(.event_type = EVENT_FLEXIBLE)
         *   ctx_sched_out(.event_type = EVENT_PINNED)
         *
         * would only update time for the pinned events.
         */
        if (is_active & EVENT_TIME) {
                /* update (and stop) ctx time */
                update_context_time(ctx);
                update_cgrp_time_from_cpuctx(cpuctx);
        }

        is_active ^= ctx->is_active; /* changed bits */

        if (!ctx->nr_active || !(is_active & EVENT_ALL))
                return;

        perf_pmu_disable(ctx->pmu);
        if (is_active & EVENT_PINNED) {
                list_for_each_entry_safe(event, tmp, &ctx->pinned_active, active_list)
                        group_sched_out(event, cpuctx, ctx);
        }

        if (is_active & EVENT_FLEXIBLE) {
                list_for_each_entry_safe(event, tmp, &ctx->flexible_active, active_list)
                        group_sched_out(event, cpuctx, ctx);

                /*
                 * Since we cleared EVENT_FLEXIBLE, also clear
                 * rotate_necessary, is will be reset by
                 * ctx_flexible_sched_in() when needed.
                 */
                ctx->rotate_necessary = 0;
        }
        perf_pmu_enable(ctx->pmu);
}

/*
 * Test whether two contexts are equivalent, i.e. whether they have both been
 * cloned from the same version of the same context.
 *
 * Equivalence is measured using a generation number in the context that is
 * incremented on each modification to it; see unclone_ctx(), list_add_event()
 * and list_del_event().
 */
static int context_equiv(struct perf_event_context *ctx1,
                         struct perf_event_context *ctx2)
{
        lockdep_assert_held(&ctx1->lock);
        lockdep_assert_held(&ctx2->lock);

        /* Pinning disables the swap optimization */
        if (ctx1->pin_count || ctx2->pin_count)
                return 0;

        /* If ctx1 is the parent of ctx2 */
        if (ctx1 == ctx2->parent_ctx && ctx1->generation == ctx2->parent_gen)
                return 1;

        /* If ctx2 is the parent of ctx1 */
        if (ctx1->parent_ctx == ctx2 && ctx1->parent_gen == ctx2->generation)
                return 1;

        /*
         * If ctx1 and ctx2 have the same parent; we flatten the parent
         * hierarchy, see perf_event_init_context().
         */
        if (ctx1->parent_ctx && ctx1->parent_ctx == ctx2->parent_ctx &&
                        ctx1->parent_gen == ctx2->parent_gen)
                return 1;

        /* Unmatched */
        return 0;
}

static void __perf_event_sync_stat(struct perf_event *event,
                                     struct perf_event *next_event)
{
        u64 value;

        if (!event->attr.inherit_stat)
                return;

        /*
         * Update the event value, we cannot use perf_event_read()
         * because we're in the middle of a context switch and have IRQs
         * disabled, which upsets smp_call_function_single(), however
         * we know the event must be on the current CPU, therefore we
         * don't need to use it.
         */
        if (event->state == PERF_EVENT_STATE_ACTIVE)
                event->pmu->read(event);

        perf_event_update_time(event);

        /*
         * In order to keep per-task stats reliable we need to flip the event
         * values when we flip the contexts.
         */
        value = local64_read(&next_event->count);
        value = local64_xchg(&event->count, value);
        local64_set(&next_event->count, value);

        swap(event->total_time_enabled, next_event->total_time_enabled);
        swap(event->total_time_running, next_event->total_time_running);

        /*
         * Since we swizzled the values, update the user visible data too.
         */
        perf_event_update_userpage(event);
        perf_event_update_userpage(next_event);
}

static void perf_event_sync_stat(struct perf_event_context *ctx,
                                   struct perf_event_context *next_ctx)
{
        struct perf_event *event, *next_event;

        if (!ctx->nr_stat)
                return;

        update_context_time(ctx);

        event = list_first_entry(&ctx->event_list,
                                   struct perf_event, event_entry);

        next_event = list_first_entry(&next_ctx->event_list,
                                        struct perf_event, event_entry);

        while (&event->event_entry != &ctx->event_list &&
               &next_event->event_entry != &next_ctx->event_list) {

                __perf_event_sync_stat(event, next_event);

                event = list_next_entry(event, event_entry);
                next_event = list_next_entry(next_event, event_entry);
        }
}

static void perf_event_context_sched_out(struct task_struct *task, int ctxn,
                                         struct task_struct *next)
{
        struct perf_event_context *ctx = task->perf_event_ctxp[ctxn];
        struct perf_event_context *next_ctx;
        struct perf_event_context *parent, *next_parent;
        struct perf_cpu_context *cpuctx;
        int do_switch = 1;
        struct pmu *pmu;

        if (likely(!ctx))
                return;

        pmu = ctx->pmu;
        cpuctx = __get_cpu_context(ctx);
        if (!cpuctx->task_ctx)
                return;

        rcu_read_lock();
        next_ctx = next->perf_event_ctxp[ctxn];
        if (!next_ctx)
                goto unlock;

        parent = rcu_dereference(ctx->parent_ctx);
        next_parent = rcu_dereference(next_ctx->parent_ctx);

        /* If neither context have a parent context; they cannot be clones. */
        if (!parent && !next_parent)
                goto unlock;

        if (next_parent == ctx || next_ctx == parent || next_parent == parent) {
                /*
                 * Looks like the two contexts are clones, so we might be
                 * able to optimize the context switch.  We lock both
                 * contexts and check that they are clones under the
                 * lock (including re-checking that neither has been
                 * uncloned in the meantime).  It doesn't matter which
                 * order we take the locks because no other cpu could
                 * be trying to lock both of these tasks.
                 */
                raw_spin_lock(&ctx->lock);
                raw_spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
                if (context_equiv(ctx, next_ctx)) {

                        WRITE_ONCE(ctx->task, next);
                        WRITE_ONCE(next_ctx->task, task);

                        perf_pmu_disable(pmu);

                        if (cpuctx->sched_cb_usage && pmu->sched_task)
                                pmu->sched_task(ctx, false);

                        /*
                         * PMU specific parts of task perf context can require
                         * additional synchronization. As an example of such
                         * synchronization see implementation details of Intel
                         * LBR call stack data profiling;
                         */
                        if (pmu->swap_task_ctx)
                                pmu->swap_task_ctx(ctx, next_ctx);
                        else
                                swap(ctx->task_ctx_data, next_ctx->task_ctx_data);

                        perf_pmu_enable(pmu);

                        /*
                         * RCU_INIT_POINTER here is safe because we've not
                         * modified the ctx and the above modification of
                         * ctx->task and ctx->task_ctx_data are immaterial
                         * since those values are always verified under
                         * ctx->lock which we're now holding.
                         */
                        RCU_INIT_POINTER(task->perf_event_ctxp[ctxn], next_ctx);
                        RCU_INIT_POINTER(next->perf_event_ctxp[ctxn], ctx);

                        do_switch = 0;

                        perf_event_sync_stat(ctx, next_ctx);
                }
                raw_spin_unlock(&next_ctx->lock);
                raw_spin_unlock(&ctx->lock);
        }
unlock:
        rcu_read_unlock();

        if (do_switch) {
                raw_spin_lock(&ctx->lock);
                perf_pmu_disable(pmu);

                if (cpuctx->sched_cb_usage && pmu->sched_task)
                        pmu->sched_task(ctx, false);
                task_ctx_sched_out(cpuctx, ctx, EVENT_ALL);

                perf_pmu_enable(pmu);
                raw_spin_unlock(&ctx->lock);
        }
}

void perf_sched_cb_dec(struct pmu *pmu)
{
        struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);

        --cpuctx->sched_cb_usage;
}


void perf_sched_cb_inc(struct pmu *pmu)
{
        struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);

        cpuctx->sched_cb_usage++;
}

/*
 * This function provides the context switch callback to the lower code
 * layer. It is invoked ONLY when the context switch callback is enabled.
 *
 * This callback is relevant even to per-cpu events; for example multi event
 * PEBS requires this to provide PID/TID information. This requires we flush
 * all queued PEBS records before we context switch to a new task.
 */
static void __perf_pmu_sched_task(struct perf_cpu_context *cpuctx, bool sched_in)
{
        struct pmu *pmu;

        pmu = cpuctx->ctx.pmu; /* software PMUs will not have sched_task */

        if (WARN_ON_ONCE(!pmu->sched_task))
                return;

        perf_ctx_lock(cpuctx, cpuctx->task_ctx);
        perf_pmu_disable(pmu);

        pmu->sched_task(cpuctx->task_ctx, sched_in);

        perf_pmu_enable(pmu);
        perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
}

static void perf_event_switch(struct task_struct *task,
                              struct task_struct *next_prev, bool sched_in);

#define for_each_task_context_nr(ctxn)                                  \
        for ((ctxn) = 0; (ctxn) < perf_nr_task_contexts; (ctxn)++)

/*
 * Called from scheduler to remove the events of the current task,
 * with interrupts disabled.
 *
 * We stop each event and update the event value in event->count.
 *
 * This does not protect us against NMI, but disable()
 * sets the disabled bit in the control field of event _before_
 * accessing the event control register. If a NMI hits, then it will
 * not restart the event.
 */
void __perf_event_task_sched_out(struct task_struct *task,
                                 struct task_struct *next)
{
        int ctxn;

        if (atomic_read(&nr_switch_events))
                perf_event_switch(task, next, false);

        for_each_task_context_nr(ctxn)
                perf_event_context_sched_out(task, ctxn, next);

        /*
         * if cgroup events exist on this CPU, then we need
         * to check if we have to switch out PMU state.
         * cgroup event are system-wide mode only
         */
        if (atomic_read(this_cpu_ptr(&perf_cgroup_events)))
                perf_cgroup_sched_out(task, next);
}

/*
 * Called with IRQs disabled
 */
static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
                              enum event_type_t event_type)
{
        ctx_sched_out(&cpuctx->ctx, cpuctx, event_type);
}

static bool perf_less_group_idx(const void *l, const void *r)
{
        const struct perf_event *le = *(const struct perf_event **)l;
        const struct perf_event *re = *(const struct perf_event **)r;

        return le->group_index < re->group_index;
}

static void swap_ptr(void *l, void *r)
{
        void **lp = l, **rp = r;

        swap(*lp, *rp);
}

static const struct min_heap_callbacks perf_min_heap = {
        .elem_size = sizeof(struct perf_event *),
        .less = perf_less_group_idx,
        .swp = swap_ptr,
};

static void __heap_add(struct min_heap *heap, struct perf_event *event)
{
        struct perf_event **itrs = heap->data;

        if (event) {
                itrs[heap->nr] = event;
                heap->nr++;
        }
}

static noinline int visit_groups_merge(struct perf_cpu_context *cpuctx,
                                struct perf_event_groups *groups, int cpu,
                                int (*func)(struct perf_event *, void *),
                                void *data)
{
#ifdef CONFIG_CGROUP_PERF
        struct cgroup_subsys_state *css = NULL;
#endif
        /* Space for per CPU and/or any CPU event iterators. */
        struct perf_event *itrs[2];
        struct min_heap event_heap;
        struct perf_event **evt;
        int ret;

        if (cpuctx) {
                event_heap = (struct min_heap){
                        .data = cpuctx->heap,
                        .nr = 0,
                        .size = cpuctx->heap_size,
                };

                lockdep_assert_held(&cpuctx->ctx.lock);

#ifdef CONFIG_CGROUP_PERF
                if (cpuctx->cgrp)
                        css = &cpuctx->cgrp->css;
#endif
        } else {
                event_heap = (struct min_heap){
                        .data = itrs,
                        .nr = 0,
                        .size = ARRAY_SIZE(itrs),
                };
                /* Events not within a CPU context may be on any CPU. */
                __heap_add(&event_heap, perf_event_groups_first(groups, -1, NULL));
        }
        evt = event_heap.data;

        __heap_add(&event_heap, perf_event_groups_first(groups, cpu, NULL));

#ifdef CONFIG_CGROUP_PERF
        for (; css; css = css->parent)
                __heap_add(&event_heap, perf_event_groups_first(groups, cpu, css->cgroup));
#endif

        min_heapify_all(&event_heap, &perf_min_heap);

        while (event_heap.nr) {
                ret = func(*evt, data);
                if (ret)
                        return ret;

                *evt = perf_event_groups_next(*evt);
                if (*evt)
                        min_heapify(&event_heap, 0, &perf_min_heap);
                else
                        min_heap_pop(&event_heap, &perf_min_heap);
        }

        return 0;
}

static int merge_sched_in(struct perf_event *event, void *data)
{
        struct perf_event_context *ctx = event->ctx;
        struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
        int *can_add_hw = data;

        if (event->state <= PERF_EVENT_STATE_OFF)
                return 0;

        if (!event_filter_match(event))
                return 0;

        if (group_can_go_on(event, cpuctx, *can_add_hw)) {
                if (!group_sched_in(event, cpuctx, ctx))
                        list_add_tail(&event->active_list, get_event_list(event));
        }

        if (event->state == PERF_EVENT_STATE_INACTIVE) {
                if (event->attr.pinned) {
                        perf_cgroup_event_disable(event, ctx);
                        perf_event_set_state(event, PERF_EVENT_STATE_ERROR);
                }

                *can_add_hw = 0;
                ctx->rotate_necessary = 1;
                perf_mux_hrtimer_restart(cpuctx);
        }

        return 0;
}

static void
ctx_pinned_sched_in(struct perf_event_context *ctx,
                    struct perf_cpu_context *cpuctx)
{
        int can_add_hw = 1;

        if (ctx != &cpuctx->ctx)
                cpuctx = NULL;

        visit_groups_merge(cpuctx, &ctx->pinned_groups,
                           smp_processor_id(),
                           merge_sched_in, &can_add_hw);
}

static void
ctx_flexible_sched_in(struct perf_event_context *ctx,
                      struct perf_cpu_context *cpuctx)
{
        int can_add_hw = 1;

        if (ctx != &cpuctx->ctx)
                cpuctx = NULL;

        visit_groups_merge(cpuctx, &ctx->flexible_groups,
                           smp_processor_id(),
                           merge_sched_in, &can_add_hw);
}

static void
ctx_sched_in(struct perf_event_context *ctx,
             struct perf_cpu_context *cpuctx,
             enum event_type_t event_type,
             struct task_struct *task)
{
        int is_active = ctx->is_active;
        u64 now;

        lockdep_assert_held(&ctx->lock);

        if (likely(!ctx->nr_events))
                return;

        ctx->is_active |= (event_type | EVENT_TIME);
        if (ctx->task) {
                if (!is_active)
                        cpuctx->task_ctx = ctx;
                else
                        WARN_ON_ONCE(cpuctx->task_ctx != ctx);
        }

        is_active ^= ctx->is_active; /* changed bits */

        if (is_active & EVENT_TIME) {
                /* start ctx time */
                now = perf_clock();
                ctx->timestamp = now;
                perf_cgroup_set_timestamp(task, ctx);
        }

        /*
         * First go through the list and put on any pinned groups
         * in order to give them the best chance of going on.
         */
        if (is_active & EVENT_PINNED)
                ctx_pinned_sched_in(ctx, cpuctx);

        /* Then walk through the lower prio flexible groups */
        if (is_active & EVENT_FLEXIBLE)
                ctx_flexible_sched_in(ctx, cpuctx);
}

static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
                             enum event_type_t event_type,
                             struct task_struct *task)
{
        struct perf_event_context *ctx = &cpuctx->ctx;

        ctx_sched_in(ctx, cpuctx, event_type, task);
}

static void perf_event_context_sched_in(struct perf_event_context *ctx,
                                        struct task_struct *task)
{
        struct perf_cpu_context *cpuctx;
        struct pmu *pmu = ctx->pmu;

        cpuctx = __get_cpu_context(ctx);
        if (cpuctx->task_ctx == ctx) {
                if (cpuctx->sched_cb_usage)
                        __perf_pmu_sched_task(cpuctx, true);
                return;
        }

        perf_ctx_lock(cpuctx, ctx);
        /*
         * We must check ctx->nr_events while holding ctx->lock, such
         * that we serialize against perf_install_in_context().
         */
        if (!ctx->nr_events)
                goto unlock;

        perf_pmu_disable(pmu);
        /*
         * We want to keep the following priority order:
         * cpu pinned (that don't need to move), task pinned,
         * cpu flexible, task flexible.
         *
         * However, if task's ctx is not carrying any pinned
         * events, no need to flip the cpuctx's events around.
         */
        if (!RB_EMPTY_ROOT(&ctx->pinned_groups.tree))
                cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
        perf_event_sched_in(cpuctx, ctx, task);

        if (cpuctx->sched_cb_usage && pmu->sched_task)
                pmu->sched_task(cpuctx->task_ctx, true);

        perf_pmu_enable(pmu);

unlock:
        perf_ctx_unlock(cpuctx, ctx);
}

/*
 * Called from scheduler to add the events of the current task
 * with interrupts disabled.
 *
 * We restore the event value and then enable it.
 *
 * This does not protect us against NMI, but enable()
 * sets the enabled bit in the control field of event _before_
 * accessing the event control register. If a NMI hits, then it will
 * keep the event running.
 */
void __perf_event_task_sched_in(struct task_struct *prev,
                                struct task_struct *task)
{
        struct perf_event_context *ctx;
        int ctxn;

        /*
         * If cgroup events exist on this CPU, then we need to check if we have
         * to switch in PMU state; cgroup event are system-wide mode only.
         *
         * Since cgroup events are CPU events, we must schedule these in before
         * we schedule in the task events.
         */
        if (atomic_read(this_cpu_ptr(&perf_cgroup_events)))
                perf_cgroup_sched_in(prev, task);

        for_each_task_context_nr(ctxn) {
                ctx = task->perf_event_ctxp[ctxn];
                if (likely(!ctx))
                        continue;

                perf_event_context_sched_in(ctx, task);
        }

        if (atomic_read(&nr_switch_events))
                perf_event_switch(task, prev, true);
}

static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count)
{
        u64 frequency = event->attr.sample_freq;
        u64 sec = NSEC_PER_SEC;
        u64 divisor, dividend;

        int count_fls, nsec_fls, frequency_fls, sec_fls;

        count_fls = fls64(count);
        nsec_fls = fls64(nsec);
        frequency_fls = fls64(frequency);
        sec_fls = 30;

        /*
         * We got @count in @nsec, with a target of sample_freq HZ
         * the target period becomes:
         *
         *             @count * 10^9
         * period = -------------------
         *          @nsec * sample_freq
         *
         */

        /*
         * Reduce accuracy by one bit such that @a and @b converge
         * to a similar magnitude.
         */
#define REDUCE_FLS(a, b)                \
do {                                    \
        if (a##_fls > b##_fls) {        \
                a >>= 1;                \
                a##_fls--;              \
        } else {                        \
                b >>= 1;                \
                b##_fls--;              \
        }                               \
} while (0)

        /*
         * Reduce accuracy until either term fits in a u64, then proceed with
         * the other, so that finally we can do a u64/u64 division.
         */
        while (count_fls + sec_fls > 64 && nsec_fls + frequency_fls > 64) {
                REDUCE_FLS(nsec, frequency);
                REDUCE_FLS(sec, count);
        }

        if (count_fls + sec_fls > 64) {
                divisor = nsec * frequency;

                while (count_fls + sec_fls > 64) {
                        REDUCE_FLS(count, sec);
                        divisor >>= 1;
                }

                dividend = count * sec;
        } else {
                dividend = count * sec;

                while (nsec_fls + frequency_fls > 64) {
                        REDUCE_FLS(nsec, frequency);
                        dividend >>= 1;
                }

                divisor = nsec * frequency;
        }

        if (!divisor)
                return dividend;

        return div64_u64(dividend, divisor);
}

static DEFINE_PER_CPU(int, perf_throttled_count);
static DEFINE_PER_CPU(u64, perf_throttled_seq);

static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count, bool disable)
{
        struct hw_perf_event *hwc = &event->hw;
        s64 period, sample_period;
        s64 delta;

        period = perf_calculate_period(event, nsec, count);

        delta = (s64)(period - hwc->sample_period);
        delta = (delta + 7) / 8; /* low pass filter */

        sample_period = hwc->sample_period + delta;

        if (!sample_period)
                sample_period = 1;

        hwc->sample_period = sample_period;

        if (local64_read(&hwc->period_left) > 8*sample_period) {
                if (disable)
                        event->pmu->stop(event, PERF_EF_UPDATE);

                local64_set(&hwc->period_left, 0);

                if (disable)
                        event->pmu->start(event, PERF_EF_RELOAD);
        }
}

/*
 * combine freq adjustment with unthrottling to avoid two passes over the
 * events. At the same time, make sure, having freq events does not change
 * the rate of unthrottling as that would introduce bias.
 */
static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx,
                                           int needs_unthr)
{
        struct perf_event *event;
        struct hw_perf_event *hwc;
        u64 now, period = TICK_NSEC;
        s64 delta;

        /*
         * only need to iterate over all events iff:
         * - context have events in frequency mode (needs freq adjust)
         * - there are events to unthrottle on this cpu
         */
        if (!(ctx->nr_freq || needs_unthr))
                return;

        raw_spin_lock(&ctx->lock);
        perf_pmu_disable(ctx->pmu);

        list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
                if (event->state != PERF_EVENT_STATE_ACTIVE)
                        continue;

                if (!event_filter_match(event))
                        continue;

                perf_pmu_disable(event->pmu);

                hwc = &event->hw;

                if (hwc->interrupts == MAX_INTERRUPTS) {
                        hwc->interrupts = 0;
                        perf_log_throttle(event, 1);
                        event->pmu->start(event, 0);
                }

                if (!event->attr.freq || !event->attr.sample_freq)
                        goto next;

                /*
                 * stop the event and update event->count
                 */
                event->pmu->stop(event, PERF_EF_UPDATE);

                now = local64_read(&event->count);
                delta = now - hwc->freq_count_stamp;
                hwc->freq_count_stamp = now;

                /*