/*
 * trace task wakeup timings
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
 *
 * Based on code from the latency_tracer, that is:
 *
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 Nadia Yvette Chambers
 */
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/sched/rt.h>
#include <linux/sched/deadline.h>
#include <trace/events/sched.h>
#include "trace.h"

static struct trace_array       *wakeup_trace;
static int __read_mostly        tracer_enabled;

static struct task_struct       *wakeup_task;
static int                      wakeup_cpu;
static int                      wakeup_current_cpu;
static unsigned                 wakeup_prio = -1;
static int                      wakeup_rt;
static int                      wakeup_dl;
static int                      tracing_dl = 0;

static arch_spinlock_t wakeup_lock =
        (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;

static void wakeup_reset(struct trace_array *tr);
static void __wakeup_reset(struct trace_array *tr);

static int save_flags;

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static int wakeup_display_graph(struct trace_array *tr, int set);
# define is_graph(tr) ((tr)->trace_flags & TRACE_ITER_DISPLAY_GRAPH)
#else
static inline int wakeup_display_graph(struct trace_array *tr, int set)
{
        return 0;
}
# define is_graph(tr) false
#endif


#ifdef CONFIG_FUNCTION_TRACER

static int wakeup_graph_entry(struct ftrace_graph_ent *trace);
static void wakeup_graph_return(struct ftrace_graph_ret *trace);

static bool function_enabled;

/*
 * Prologue for the wakeup function tracers.
 *
 * Returns 1 if it is OK to continue, and preemption
 *            is disabled and data->disabled is incremented.
 *         0 if the trace is to be ignored, and preemption
 *            is not disabled and data->disabled is
 *            kept the same.
 *
 * Note, this function is also used outside this ifdef but
 *  inside the #ifdef of the function graph tracer below.
 *  This is OK, since the function graph tracer is
 *  dependent on the function tracer.
 */
static int
func_prolog_preempt_disable(struct trace_array *tr,
                            struct trace_array_cpu **data,
                            int *pc)
{
        long disabled;
        int cpu;

        if (likely(!wakeup_task))
                return 0;

        *pc = preempt_count();
        preempt_disable_notrace();

        cpu = raw_smp_processor_id();
        if (cpu != wakeup_current_cpu)
                goto out_enable;

        *data = per_cpu_ptr(tr->trace_buffer.data, cpu);
        disabled = atomic_inc_return(&(*data)->disabled);
        if (unlikely(disabled != 1))
                goto out;

        return 1;

out:
        atomic_dec(&(*data)->disabled);

out_enable:
        preempt_enable_notrace();
        return 0;
}

/*
 * wakeup uses its own tracer function to keep the overhead down:
 */
static void
wakeup_tracer_call(unsigned long ip, unsigned long parent_ip,
                   struct ftrace_ops *op, struct pt_regs *pt_regs)
{
        struct trace_array *tr = wakeup_trace;
        struct trace_array_cpu *data;
        unsigned long flags;
        int pc;

        if (!func_prolog_preempt_disable(tr, &data, &pc))
                return;

        local_irq_save(flags);
        trace_function(tr, ip, parent_ip, flags, pc);
        local_irq_restore(flags);

        atomic_dec(&data->disabled);
        preempt_enable_notrace();
}

static int register_wakeup_function(struct trace_array *tr, int graph, int set)
{
        int ret;

        /* 'set' is set if TRACE_ITER_FUNCTION is about to be set */
        if (function_enabled || (!set && !(tr->trace_flags & TRACE_ITER_FUNCTION)))
                return 0;

        if (graph)
                ret = register_ftrace_graph(&wakeup_graph_return,
                                            &wakeup_graph_entry);
        else
                ret = register_ftrace_function(tr->ops);

        if (!ret)
                function_enabled = true;

        return ret;
}

static void unregister_wakeup_function(struct trace_array *tr, int graph)
{
        if (!function_enabled)
                return;

        if (graph)
                unregister_ftrace_graph();
        else
                unregister_ftrace_function(tr->ops);

        function_enabled = false;
}

static int wakeup_function_set(struct trace_array *tr, u32 mask, int set)
{
        if (!(mask & TRACE_ITER_FUNCTION))
                return 0;

        if (set)
                register_wakeup_function(tr, is_graph(tr), 1);
        else
                unregister_wakeup_function(tr, is_graph(tr));
        return 1;
}
#else
static int register_wakeup_function(struct trace_array *tr, int graph, int set)
{
        return 0;
}
static void unregister_wakeup_function(struct trace_array *tr, int graph) { }
static int wakeup_function_set(struct trace_array *tr, u32 mask, int set)
{
        return 0;
}
#endif /* CONFIG_FUNCTION_TRACER */

static int wakeup_flag_changed(struct trace_array *tr, u32 mask, int set)
{
        struct tracer *tracer = tr->current_trace;

        if (wakeup_function_set(tr, mask, set))
                return 0;

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
        if (mask & TRACE_ITER_DISPLAY_GRAPH)
                return wakeup_display_graph(tr, set);
#endif

        return trace_keep_overwrite(tracer, mask, set);
}

static int start_func_tracer(struct trace_array *tr, int graph)
{
        int ret;

        ret = register_wakeup_function(tr, graph, 0);

        if (!ret && tracing_is_enabled())
                tracer_enabled = 1;
        else
                tracer_enabled = 0;

        return ret;
}

static void stop_func_tracer(struct trace_array *tr, int graph)
{
        tracer_enabled = 0;

        unregister_wakeup_function(tr, graph);
}

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static int wakeup_display_graph(struct trace_array *tr, int set)
{
        if (!(is_graph(tr) ^ set))
                return 0;

        stop_func_tracer(tr, !set);

        wakeup_reset(wakeup_trace);
        tr->max_latency = 0;

        return start_func_tracer(tr, set);
}

static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
{
        struct trace_array *tr = wakeup_trace;
        struct trace_array_cpu *data;
        unsigned long flags;
        int pc, ret = 0;

        if (!func_prolog_preempt_disable(tr, &data, &pc))
                return 0;

        local_save_flags(flags);
        ret = __trace_graph_entry(tr, trace, flags, pc);
        atomic_dec(&data->disabled);
        preempt_enable_notrace();

        return ret;
}

static void wakeup_graph_return(struct ftrace_graph_ret *trace)
{
        struct trace_array *tr = wakeup_trace;
        struct trace_array_cpu *data;
        unsigned long flags;
        int pc;

        if (!func_prolog_preempt_disable(tr, &data, &pc))
                return;

        local_save_flags(flags);
        __trace_graph_return(tr, trace, flags, pc);
        atomic_dec(&data->disabled);

        preempt_enable_notrace();
        return;
}

static void wakeup_trace_open(struct trace_iterator *iter)
{
        if (is_graph(iter->tr))
                graph_trace_open(iter);
}

static void wakeup_trace_close(struct trace_iterator *iter)
{
        if (iter->private)
                graph_trace_close(iter);
}

#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_PROC | \
                            TRACE_GRAPH_PRINT_ABS_TIME | \
                            TRACE_GRAPH_PRINT_DURATION)

static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
{
        /*
         * In graph mode call the graph tracer output function,
         * otherwise go with the TRACE_FN event handler
         */
        if (is_graph(iter->tr))
                return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);

        return TRACE_TYPE_UNHANDLED;
}

static void wakeup_print_header(struct seq_file *s)
{
        if (is_graph(wakeup_trace))
                print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
        else
                trace_default_header(s);
}

static void
__trace_function(struct trace_array *tr,
                 unsigned long ip, unsigned long parent_ip,
                 unsigned long flags, int pc)
{
        if (is_graph(tr))
                trace_graph_function(tr, ip, parent_ip, flags, pc);
        else
                trace_function(tr, ip, parent_ip, flags, pc);
}
#else
#define __trace_function trace_function

static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
{
        return TRACE_TYPE_UNHANDLED;
}

static void wakeup_trace_open(struct trace_iterator *iter) { }
static void wakeup_trace_close(struct trace_iterator *iter) { }

#ifdef CONFIG_FUNCTION_TRACER
static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
{
        return -1;
}
static void wakeup_graph_return(struct ftrace_graph_ret *trace) { }
static void wakeup_print_header(struct seq_file *s)
{
        trace_default_header(s);
}
#else
static void wakeup_print_header(struct seq_file *s)
{
        trace_latency_header(s);
}
#endif /* CONFIG_FUNCTION_TRACER */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

/*
 * Should this new latency be reported/recorded?
 */
static bool report_latency(struct trace_array *tr, cycle_t delta)
{
        if (tracing_thresh) {
                if (delta < tracing_thresh)
                        return false;
        } else {
                if (delta <= tr->max_latency)
                        return false;
        }
        return true;
}

static void
probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu)
{
        if (task != wakeup_task)
                return;

        wakeup_current_cpu = cpu;
}

static void
tracing_sched_switch_trace(struct trace_array *tr,
                           struct task_struct *prev,
                           struct task_struct *next,
                           unsigned long flags, int pc)
{
        struct trace_event_call *call = &event_context_switch;
        struct ring_buffer *buffer = tr->trace_buffer.buffer;
        struct ring_buffer_event *event;
        struct ctx_switch_entry *entry;

        event = trace_buffer_lock_reserve(buffer, TRACE_CTX,
                                          sizeof(*entry), flags, pc);
        if (!event)
                return;
        entry   = ring_buffer_event_data(event);
        entry->prev_pid                 = prev->pid;
        entry->prev_prio                = prev->prio;
        entry->prev_state               = prev->state;
        entry->next_pid                 = next->pid;
        entry->next_prio                = next->prio;
        entry->next_state               = next->state;
        entry->next_cpu = task_cpu(next);

        if (!call_filter_check_discard(call, entry, buffer, event))
                trace_buffer_unlock_commit(tr, buffer, event, flags, pc);
}

static void
tracing_sched_wakeup_trace(struct trace_array *tr,
                           struct task_struct *wakee,
                           struct task_struct *curr,
                           unsigned long flags, int pc)
{
        struct trace_event_call *call = &event_wakeup;
        struct ring_buffer_event *event;
        struct ctx_switch_entry *entry;
        struct ring_buffer *buffer = tr->trace_buffer.buffer;

        event = trace_buffer_lock_reserve(buffer, TRACE_WAKE,
                                          sizeof(*entry), flags, pc);
        if (!event)
                return;
        entry   = ring_buffer_event_data(event);
        entry->prev_pid                 = curr->pid;
        entry->prev_prio                = curr->prio;
        entry->prev_state               = curr->state;
        entry->next_pid                 = wakee->pid;
        entry->next_prio                = wakee->prio;
        entry->next_state               = wakee->state;
        entry->next_cpu                 = task_cpu(wakee);

        if (!call_filter_check_discard(call, entry, buffer, event))
                trace_buffer_unlock_commit(tr, buffer, event, flags, pc);
}

static void notrace
probe_wakeup_sched_switch(void *ignore, bool preempt,
                          struct task_struct *prev, struct task_struct *next)
{
        struct trace_array_cpu *data;
        cycle_t T0, T1, delta;
        unsigned long flags;
        long disabled;
        int cpu;
        int pc;

        tracing_record_cmdline(prev);

        if (unlikely(!tracer_enabled))
                return;

        /*
         * When we start a new trace, we set wakeup_task to NULL
         * and then set tracer_enabled = 1. We want to make sure
         * that another CPU does not see the tracer_enabled = 1
         * and the wakeup_task with an older task, that might
         * actually be the same as next.
         */
        smp_rmb();

        if (next != wakeup_task)
                return;

        pc = preempt_count();

        /* disable local data, not wakeup_cpu data */
        cpu = raw_smp_processor_id();
        disabled = atomic_inc_return(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
        if (likely(disabled != 1))
                goto out;

        local_irq_save(flags);
        arch_spin_lock(&wakeup_lock);

        /* We could race with grabbing wakeup_lock */
        if (unlikely(!tracer_enabled || next != wakeup_task))
                goto out_unlock;

        /* The task we are waiting for is waking up */
        data = per_cpu_ptr(wakeup_trace->trace_buffer.data, wakeup_cpu);

        __trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
        tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);

        T0 = data->preempt_timestamp;
        T1 = ftrace_now(cpu);
        delta = T1-T0;

        if (!report_latency(wakeup_trace, delta))
                goto out_unlock;

        if (likely(!is_tracing_stopped())) {
                wakeup_trace->max_latency = delta;
                update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
        }

out_unlock:
        __wakeup_reset(wakeup_trace);
        arch_spin_unlock(&wakeup_lock);
        local_irq_restore(flags);
out:
        atomic_dec(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
}

static void __wakeup_reset(struct trace_array *tr)
{
        wakeup_cpu = -1;
        wakeup_prio = -1;
        tracing_dl = 0;

        if (wakeup_task)
                put_task_struct(wakeup_task);

        wakeup_task = NULL;
}

static void wakeup_reset(struct trace_array *tr)
{
        unsigned long flags;

        tracing_reset_online_cpus(&tr->trace_buffer);

        local_irq_save(flags);
        arch_spin_lock(&wakeup_lock);
        __wakeup_reset(tr);
        arch_spin_unlock(&wakeup_lock);
        local_irq_restore(flags);
}

static void
probe_wakeup(void *ignore, struct task_struct *p)
{
        struct trace_array_cpu *data;
        int cpu = smp_processor_id();
        unsigned long flags;
        long disabled;
        int pc;

        if (likely(!tracer_enabled))
                return;

        tracing_record_cmdline(p);
        tracing_record_cmdline(current);

        /*
         * Semantic is like this:
         *  - wakeup tracer handles all tasks in the system, independently
         *    from their scheduling class;
         *  - wakeup_rt tracer handles tasks belonging to sched_dl and
         *    sched_rt class;
         *  - wakeup_dl handles tasks belonging to sched_dl class only.
         */
        if (tracing_dl || (wakeup_dl && !dl_task(p)) ||
            (wakeup_rt && !dl_task(p) && !rt_task(p)) ||
            (!dl_task(p) && (p->prio >= wakeup_prio || p->prio >= current->prio)))
                return;

        pc = preempt_count();
        disabled = atomic_inc_return(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
        if (unlikely(disabled != 1))
                goto out;

        /* interrupts should be off from try_to_wake_up */
        arch_spin_lock(&wakeup_lock);

        /* check for races. */
        if (!tracer_enabled || tracing_dl ||
            (!dl_task(p) && p->prio >= wakeup_prio))
                goto out_locked;

        /* reset the trace */
        __wakeup_reset(wakeup_trace);

        wakeup_cpu = task_cpu(p);
        wakeup_current_cpu = wakeup_cpu;
        wakeup_prio = p->prio;

        /*
         * Once you start tracing a -deadline task, don't bother tracing
         * another task until the first one wakes up.
         */
        if (dl_task(p))
                tracing_dl = 1;
        else
                tracing_dl = 0;

        wakeup_task = p;
        get_task_struct(wakeup_task);

        local_save_flags(flags);

        data = per_cpu_ptr(wakeup_trace->trace_buffer.data, wakeup_cpu);
        data->preempt_timestamp = ftrace_now(cpu);
        tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);

        /*
         * We must be careful in using CALLER_ADDR2. But since wake_up
         * is not called by an assembly function  (where as schedule is)
         * it should be safe to use it here.
         */
        __trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);

out_locked:
        arch_spin_unlock(&wakeup_lock);
out:
        atomic_dec(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled);
}

static void start_wakeup_tracer(struct trace_array *tr)
{
        int ret;

        ret = register_trace_sched_wakeup(probe_wakeup, NULL);
        if (ret) {
                pr_info("wakeup trace: Couldn't activate tracepoint"
                        " probe to kernel_sched_wakeup\n");
                return;
        }

        ret = register_trace_sched_wakeup_new(probe_wakeup, NULL);
        if (ret) {
                pr_info("wakeup trace: Couldn't activate tracepoint"
                        " probe to kernel_sched_wakeup_new\n");
                goto fail_deprobe;
        }

        ret = register_trace_sched_switch(probe_wakeup_sched_switch, NULL);
        if (ret) {
                pr_info("sched trace: Couldn't activate tracepoint"
                        " probe to kernel_sched_switch\n");
                goto fail_deprobe_wake_new;
        }

        ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
        if (ret) {
                pr_info("wakeup trace: Couldn't activate tracepoint"
                        " probe to kernel_sched_migrate_task\n");
                return;
        }

        wakeup_reset(tr);

        /*
         * Don't let the tracer_enabled = 1 show up before
         * the wakeup_task is reset. This may be overkill since
         * wakeup_reset does a spin_unlock after setting the
         * wakeup_task to NULL, but I want to be safe.
         * This is a slow path anyway.
         */
        smp_wmb();

        if (start_func_tracer(tr, is_graph(tr)))
                printk(KERN_ERR "failed to start wakeup tracer\n");

        return;
fail_deprobe_wake_new:
        unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
fail_deprobe:
        unregister_trace_sched_wakeup(probe_wakeup, NULL);
}

static void stop_wakeup_tracer(struct trace_array *tr)
{
        tracer_enabled = 0;
        stop_func_tracer(tr, is_graph(tr));
        unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL);
        unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
        unregister_trace_sched_wakeup(probe_wakeup, NULL);
        unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
}

static bool wakeup_busy;

static int __wakeup_tracer_init(struct trace_array *tr)
{
        save_flags = tr->trace_flags;

        /* non overwrite screws up the latency tracers */
        set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 1);
        set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, 1);

        tr->max_latency = 0;
        wakeup_trace = tr;
        ftrace_init_array_ops(tr, wakeup_tracer_call);
        start_wakeup_tracer(tr);

        wakeup_busy = true;
        return 0;
}

static int wakeup_tracer_init(struct trace_array *tr)
{
        if (wakeup_busy)
                return -EBUSY;

        wakeup_dl = 0;
        wakeup_rt = 0;
        return __wakeup_tracer_init(tr);
}

static int wakeup_rt_tracer_init(struct trace_array *tr)
{
        if (wakeup_busy)
                return -EBUSY;

        wakeup_dl = 0;
        wakeup_rt = 1;
        return __wakeup_tracer_init(tr);
}

static int wakeup_dl_tracer_init(struct trace_array *tr)
{
        if (wakeup_busy)
                return -EBUSY;

        wakeup_dl = 1;
        wakeup_rt = 0;
        return __wakeup_tracer_init(tr);
}

static void wakeup_tracer_reset(struct trace_array *tr)
{
        int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
        int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;

        stop_wakeup_tracer(tr);
        /* make sure we put back any tasks we are tracing */
        wakeup_reset(tr);

        set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag);
        set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
        ftrace_reset_array_ops(tr);
        wakeup_busy = false;
}

static void wakeup_tracer_start(struct trace_array *tr)
{
        wakeup_reset(tr);
        tracer_enabled = 1;
}

static void wakeup_tracer_stop(struct trace_array *tr)
{
        tracer_enabled = 0;
}

static struct tracer wakeup_tracer __read_mostly =
{
        .name           = "wakeup",
        .init           = wakeup_tracer_init,
        .reset          = wakeup_tracer_reset,
        .start          = wakeup_tracer_start,
        .stop           = wakeup_tracer_stop,
        .print_max      = true,
        .print_header   = wakeup_print_header,
        .print_line     = wakeup_print_line,
        .flag_changed   = wakeup_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
        .selftest    = trace_selftest_startup_wakeup,
#endif
        .open           = wakeup_trace_open,
        .close          = wakeup_trace_close,
        .allow_instances = true,
        .use_max_tr     = true,
};

static struct tracer wakeup_rt_tracer __read_mostly =
{
        .name           = "wakeup_rt",
        .init           = wakeup_rt_tracer_init,
        .reset          = wakeup_tracer_reset,
        .start          = wakeup_tracer_start,
        .stop           = wakeup_tracer_stop,
        .print_max      = true,
        .print_header   = wakeup_print_header,
        .print_line     = wakeup_print_line,
        .flag_changed   = wakeup_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
        .selftest    = trace_selftest_startup_wakeup,
#endif
        .open           = wakeup_trace_open,
        .close          = wakeup_trace_close,
        .allow_instances = true,
        .use_max_tr     = true,
};

static struct tracer wakeup_dl_tracer __read_mostly =
{
        .name           = "wakeup_dl",
        .init           = wakeup_dl_tracer_init,
        .reset          = wakeup_tracer_reset,
        .start          = wakeup_tracer_start,
        .stop           = wakeup_tracer_stop,
        .print_max      = true,
        .print_header   = wakeup_print_header,
        .print_line     = wakeup_print_line,
        .flag_changed   = wakeup_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
        .selftest    = trace_selftest_startup_wakeup,
#endif
        .open           = wakeup_trace_open,
        .close          = wakeup_trace_close,
        .use_max_tr     = true,
};

__init static int init_wakeup_tracer(void)
{
        int ret;

        ret = register_tracer(&wakeup_tracer);
        if (ret)
                return ret;

        ret = register_tracer(&wakeup_rt_tracer);
        if (ret)
                return ret;

        ret = register_tracer(&wakeup_dl_tracer);
        if (ret)
                return ret;

        return 0;
}
core_initcall(init_wakeup_tracer);