// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2013  Davidlohr Bueso <davidlohr@hp.com>
 *
 * futex-requeue: Block a bunch of threads on futex1 and requeue them
 *                on futex2, N at a time.
 *
 * This program is particularly useful to measure the latency of nthread
 * requeues without waking up any tasks -- thus mimicking a regular futex_wait.
 */

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

static u_int32_t futex1 = 0, futex2 = 0;

/*
 * How many tasks to requeue at a time.
 * Default to 1 in order to make the kernel work more.
 */
static unsigned int nrequeue = 1;

static 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 requeuetime_stats, requeued_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('q', "nrequeue", &nrequeue, "Specify amount of threads to requeue 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_requeue_usage[] = {
        "perf bench futex requeue <options>",
        NULL
};

static void print_summary(void)
{
        double requeuetime_avg = avg_stats(&requeuetime_stats);
        double requeuetime_stddev = stddev_stats(&requeuetime_stats);
        unsigned int requeued_avg = avg_stats(&requeued_stats);

        printf("Requeued %d of %d threads in %.4f ms (+-%.2f%%)\n",
               requeued_avg,
               nthreads,
               requeuetime_avg / USEC_PER_MSEC,
               rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
}

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);

        futex_wait(&futex1, 0, NULL, futex_flag);
        return NULL;
}

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

        argc = parse_options(argc, argv, options, bench_futex_requeue_usage, 0);
        if (argc)
                goto err;

        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;

        if (nrequeue > nthreads)
                nrequeue = nthreads;

        printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %p), "
               "%d at a time.\n\n",  getpid(), nthreads,
               fshared ? "shared":"private", &futex1, &futex2, nrequeue);

        init_stats(&requeued_stats);
        init_stats(&requeuetime_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 nrequeued = 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 requeueing */
                gettimeofday(&start, NULL);
                while (nrequeued < nthreads) {
                        /*
                         * Do not wakeup any tasks blocked on futex1, allowing
                         * us to really measure futex_wait functionality.
                         */
                        nrequeued += futex_cmp_requeue(&futex1, 0, &futex2, 0,
                                                       nrequeue, futex_flag);
                }

                gettimeofday(&end, NULL);
                timersub(&end, &start, &runtime);

                update_stats(&requeued_stats, nrequeued);
                update_stats(&requeuetime_stats, runtime.tv_usec);

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

                /* everybody should be blocked on futex2, wake'em up */
                nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
                if (nthreads != nrequeued)
                        warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads);

                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;
err:
        usage_with_options(bench_futex_requeue_usage, options);
        exit(EXIT_FAILURE);
}