// 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 (in the non-pi case) -- thus
 * mimicking a regular futex_wait.
 */

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

#include <signal.h>
#include "../util/mutex.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 <perf/cpumap.h>
#include "bench.h"
#include "futex.h"

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

static u_int32_t futex1 = 0, futex2 = 0;

static pthread_t *worker;
static bool done = false;
static struct mutex thread_lock;
static struct cond thread_parent, thread_worker;
static struct stats requeuetime_stats, requeued_stats;
static unsigned int threads_starting;
static int futex_flag = 0;

static struct bench_futex_parameters params = {
        .nbuckets = -1,
        /*
         * How many tasks to requeue at a time.
         * Default to 1 in order to make the kernel work more.
         */
        .nrequeue = 1,
};

static const struct option options[] = {
        OPT_INTEGER( 'b', "buckets", &params.nbuckets, "Specify amount of hash buckets"),
        OPT_UINTEGER('t', "threads",  &params.nthreads, "Specify amount of threads"),
        OPT_UINTEGER('q', "nrequeue", &params.nrequeue, "Specify amount of threads to requeue at once"),
        OPT_BOOLEAN( 's', "silent",   &params.silent, "Silent mode: do not display data/details"),
        OPT_BOOLEAN( 'S', "shared",   &params.fshared, "Use shared futexes instead of private ones"),
        OPT_BOOLEAN( 'm', "mlockall", &params.mlockall, "Lock all current and future memory"),
        OPT_BOOLEAN( 'B', "broadcast", &params.broadcast, "Requeue all threads at once"),
        OPT_BOOLEAN( 'p', "pi", &params.pi, "Use PI-aware variants of FUTEX_CMP_REQUEUE"),

        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,
               params.nthreads,
               requeuetime_avg / USEC_PER_MSEC,
               rel_stddev_stats(requeuetime_stddev, requeuetime_avg));
        futex_print_nbuckets(&params);
}

static void *workerfn(void *arg __maybe_unused)
{
        int ret;

        mutex_lock(&thread_lock);
        threads_starting--;
        if (!threads_starting)
                cond_signal(&thread_parent);
        cond_wait(&thread_worker, &thread_lock);
        mutex_unlock(&thread_lock);

        while (1) {
                if (!params.pi) {
                        ret = futex_wait(&futex1, 0, NULL, futex_flag);
                        if (!ret)
                                break;

                        if (ret && errno != EAGAIN) {
                                if (!params.silent)
                                        warnx("futex_wait");
                                break;
                        }
                } else {
                        ret = futex_wait_requeue_pi(&futex1, 0, &futex2,
                                                    NULL, futex_flag);
                        if (!ret) {
                                /* got the lock at futex2 */
                                futex_unlock_pi(&futex2, futex_flag);
                                break;
                        }

                        if (ret && errno != EAGAIN) {
                                if (!params.silent)
                                        warnx("futex_wait_requeue_pi");
                                break;
                        }
                }
        }

        return NULL;
}

static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
{
        cpu_set_t *cpuset;
        unsigned int i;
        int nrcpus = cpu__max_cpu().cpu;
        size_t size;

        threads_starting = params.nthreads;

        cpuset = CPU_ALLOC(nrcpus);
        BUG_ON(!cpuset);
        size = CPU_ALLOC_SIZE(nrcpus);

        /* create and block all threads */
        for (i = 0; i < params.nthreads; i++) {
                pthread_attr_t thread_attr;

                pthread_attr_init(&thread_attr);
                CPU_ZERO_S(size, cpuset);
                CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);

                if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
                        CPU_FREE(cpuset);
                        err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
                }

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

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;
        struct perf_cpu_map *cpu;

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

        cpu = perf_cpu_map__new_online_cpus();
        if (!cpu)
                err(EXIT_FAILURE, "cpu_map__new");

        memset(&act, 0, sizeof(act));
        sigfillset(&act.sa_mask);
        act.sa_sigaction = toggle_done;
        sigaction(SIGINT, &act, NULL);

        if (params.mlockall) {
                if (mlockall(MCL_CURRENT | MCL_FUTURE))
                        err(EXIT_FAILURE, "mlockall");
        }

        if (!params.nthreads)
                params.nthreads = perf_cpu_map__nr(cpu);

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

        if (!params.fshared)
                futex_flag = FUTEX_PRIVATE_FLAG;

        if (params.nrequeue > params.nthreads)
                params.nrequeue = params.nthreads;

        if (params.broadcast)
                params.nrequeue = params.nthreads;

        futex_set_nbuckets_param(&params);

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

        init_stats(&requeued_stats);
        init_stats(&requeuetime_stats);
        mutex_init(&thread_lock);
        cond_init(&thread_parent);
        cond_init(&thread_worker);

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

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

                /* make sure all threads are already blocked */
                mutex_lock(&thread_lock);
                while (threads_starting)
                        cond_wait(&thread_parent, &thread_lock);
                cond_broadcast(&thread_worker);
                mutex_unlock(&thread_lock);

                usleep(100000);

                /* Ok, all threads are patiently blocked, start requeueing */
                gettimeofday(&start, NULL);
                while (nrequeued < params.nthreads) {
                        int r;

                        /*
                         * For the regular non-pi case, do not wakeup any tasks
                         * blocked on futex1, allowing us to really measure
                         * futex_wait functionality. For the PI case the first
                         * waiter is always awoken.
                         */
                        if (!params.pi) {
                                r = futex_cmp_requeue(&futex1, 0, &futex2, 0,
                                                      params.nrequeue,
                                                      futex_flag);
                        } else {
                                r = futex_cmp_requeue_pi(&futex1, 0, &futex2,
                                                         params.nrequeue,
                                                         futex_flag);
                                wakeups++; /* assume no error */
                        }

                        if (r < 0)
                                err(EXIT_FAILURE, "couldn't requeue from %p to %p",
                                    &futex1, &futex2);

                        nrequeued += r;
                }

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

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

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

                }

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

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

        /* cleanup & report results */
        cond_destroy(&thread_parent);
        cond_destroy(&thread_worker);
        mutex_destroy(&thread_lock);

        print_summary();

        free(worker);
        perf_cpu_map__put(cpu);
        return ret;
err:
        usage_with_options(bench_futex_requeue_usage, options);
        exit(EXIT_FAILURE);
}