/*
 * Copyright (C) 2013  Davidlohr Bueso <davidlohr@hp.com>
 *
 * futex-wake: Block a bunch of threads on a futex and wake'em up, N at a time.
 *
 * This program is particularly useful to measure the latency of nthread wakeups
 * in non-error situations:  all waiters are queued and all wake calls wakeup
 * one or more tasks, and thus the waitqueue is never empty.
 */

/* For the CLR_() macros */
#include <pthread.h>

#include <signal.h>
#include "../util/stat.h"
#include <subcmd/parse-options.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/time64.h>
#include <errno.h>
#include "bench.h"
#include "futex.h"

#include <err.h>
#include <stdlib.h>
#include <sys/time.h>

/* all threads will block on the same futex */
static u_int32_t futex1 = 0;

/*
 * How many wakeups to do at a time.
 * Default to 1 in order to make the kernel work more.
 */
static unsigned int nwakes = 1;

pthread_t *worker;
static bool done = false, silent = false, fshared = false;
static pthread_mutex_t thread_lock;
static pthread_cond_t thread_parent, thread_worker;
static struct stats waketime_stats, wakeup_stats;
static unsigned int ncpus, threads_starting, nthreads = 0;
static int futex_flag = 0;

static const struct option options[] = {
        OPT_UINTEGER('t', "threads", &nthreads, "Specify amount of threads"),
        OPT_UINTEGER('w', "nwakes",  &nwakes,   "Specify amount of threads to wake at once"),
        OPT_BOOLEAN( 's', "silent",  &silent,   "Silent mode: do not display data/details"),
        OPT_BOOLEAN( 'S', "shared",  &fshared,  "Use shared futexes instead of private ones"),
        OPT_END()
};

static const char * const bench_futex_wake_usage[] = {
        "perf bench futex wake <options>",
        NULL
};

static void *workerfn(void *arg __maybe_unused)
{
        pthread_mutex_lock(&thread_lock);
        threads_starting--;
        if (!threads_starting)
                pthread_cond_signal(&thread_parent);
        pthread_cond_wait(&thread_worker, &thread_lock);
        pthread_mutex_unlock(&thread_lock);

        while (1) {
                if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR)
                        break;
        }

        pthread_exit(NULL);
        return NULL;
}

static void print_summary(void)
{
        double waketime_avg = avg_stats(&waketime_stats);
        double waketime_stddev = stddev_stats(&waketime_stats);
        unsigned int wakeup_avg = avg_stats(&wakeup_stats);

        printf("Wokeup %d of %d threads in %.4f ms (+-%.2f%%)\n",
               wakeup_avg,
               nthreads,
               waketime_avg / USEC_PER_MSEC,
               rel_stddev_stats(waketime_stddev, waketime_avg));
}

static void block_threads(pthread_t *w,
                          pthread_attr_t thread_attr)
{
        cpu_set_t cpu;
        unsigned int i;

        threads_starting = nthreads;

        /* create and block all threads */
        for (i = 0; i < nthreads; i++) {
                CPU_ZERO(&cpu);
                CPU_SET(i % ncpus, &cpu);

                if (pthread_attr_setaffinity_np(&thread_attr, sizeof(cpu_set_t), &cpu))
                        err(EXIT_FAILURE, "pthread_attr_setaffinity_np");

                if (pthread_create(&w[i], &thread_attr, workerfn, NULL))
                        err(EXIT_FAILURE, "pthread_create");
        }
}

static void toggle_done(int sig __maybe_unused,
                        siginfo_t *info __maybe_unused,
                        void *uc __maybe_unused)
{
        done = true;
}

int bench_futex_wake(int argc, const char **argv,
                     const char *prefix __maybe_unused)
{
        int ret = 0;
        unsigned int i, j;
        struct sigaction act;
        pthread_attr_t thread_attr;

        argc = parse_options(argc, argv, options, bench_futex_wake_usage, 0);
        if (argc) {
                usage_with_options(bench_futex_wake_usage, options);
                exit(EXIT_FAILURE);
        }

        ncpus = sysconf(_SC_NPROCESSORS_ONLN);

        sigfillset(&act.sa_mask);
        act.sa_sigaction = toggle_done;
        sigaction(SIGINT, &act, NULL);

        if (!nthreads)
                nthreads = ncpus;

        worker = calloc(nthreads, sizeof(*worker));
        if (!worker)
                err(EXIT_FAILURE, "calloc");

        if (!fshared)
                futex_flag = FUTEX_PRIVATE_FLAG;

        printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), "
               "waking up %d at a time.\n\n",
               getpid(), nthreads, fshared ? "shared":"private",  &futex1, nwakes);

        init_stats(&wakeup_stats);
        init_stats(&waketime_stats);
        pthread_attr_init(&thread_attr);
        pthread_mutex_init(&thread_lock, NULL);
        pthread_cond_init(&thread_parent, NULL);
        pthread_cond_init(&thread_worker, NULL);

        for (j = 0; j < bench_repeat && !done; j++) {
                unsigned int nwoken = 0;
                struct timeval start, end, runtime;

                /* create, launch & block all threads */
                block_threads(worker, thread_attr);

                /* make sure all threads are already blocked */
                pthread_mutex_lock(&thread_lock);
                while (threads_starting)
                        pthread_cond_wait(&thread_parent, &thread_lock);
                pthread_cond_broadcast(&thread_worker);
                pthread_mutex_unlock(&thread_lock);

                usleep(100000);

                /* Ok, all threads are patiently blocked, start waking folks up */
                gettimeofday(&start, NULL);
                while (nwoken != nthreads)
                        nwoken += futex_wake(&futex1, nwakes, futex_flag);
                gettimeofday(&end, NULL);
                timersub(&end, &start, &runtime);

                update_stats(&wakeup_stats, nwoken);
                update_stats(&waketime_stats, runtime.tv_usec);

                if (!silent) {
                        printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n",
                               j + 1, nwoken, nthreads, runtime.tv_usec / (double)USEC_PER_MSEC);
                }

                for (i = 0; i < nthreads; i++) {
                        ret = pthread_join(worker[i], NULL);
                        if (ret)
                                err(EXIT_FAILURE, "pthread_join");
                }

        }

        /* cleanup & report results */
        pthread_cond_destroy(&thread_parent);
        pthread_cond_destroy(&thread_worker);
        pthread_mutex_destroy(&thread_lock);
        pthread_attr_destroy(&thread_attr);

        print_summary();

        free(worker);
        return ret;
}