/*
 * Context switch microbenchmark.
 *
 * Copyright (C) 2015 Anton Blanchard <anton@au.ibm.com>, IBM
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#define _GNU_SOURCE
#include <sched.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <getopt.h>
#include <signal.h>
#include <assert.h>
#include <pthread.h>
#include <limits.h>
#include <sys/time.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/shm.h>
#include <linux/futex.h>
#ifdef __powerpc__
#include <altivec.h>
#endif
#include "../utils.h"

static unsigned int timeout = 30;

static int touch_vdso;
struct timeval tv;

static int touch_fp = 1;
double fp;

static int touch_vector = 1;
vector int a, b, c;

#ifdef __powerpc__
static int touch_altivec = 1;

/*
 * Note: LTO (Link Time Optimisation) doesn't play well with this function
 * attribute. Be very careful enabling LTO for this test.
 */
static void __attribute__((__target__("no-vsx"))) altivec_touch_fn(void)
{
        c = a + b;
}
#endif

static void touch(void)
{
        if (touch_vdso)
                gettimeofday(&tv, NULL);

        if (touch_fp)
                fp += 0.1;

#ifdef __powerpc__
        if (touch_altivec)
                altivec_touch_fn();
#endif

        if (touch_vector)
                c = a + b;

        asm volatile("# %0 %1 %2": : "r"(&tv), "r"(&fp), "r"(&c));
}

static void start_thread_on(void *(*fn)(void *), void *arg, unsigned long cpu)
{
        pthread_t tid;
        cpu_set_t cpuset;
        pthread_attr_t attr;

        CPU_ZERO(&cpuset);
        CPU_SET(cpu, &cpuset);

        pthread_attr_init(&attr);

        if (pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset)) {
                perror("pthread_attr_setaffinity_np");
                exit(1);
        }

        if (pthread_create(&tid, &attr, fn, arg)) {
                perror("pthread_create");
                exit(1);
        }
}

static void start_process_on(void *(*fn)(void *), void *arg, unsigned long cpu)
{
        int pid;
        cpu_set_t cpuset;

        pid = fork();
        if (pid == -1) {
                perror("fork");
                exit(1);
        }

        if (pid)
                return;

        CPU_ZERO(&cpuset);
        CPU_SET(cpu, &cpuset);

        if (sched_setaffinity(0, sizeof(cpuset), &cpuset)) {
                perror("sched_setaffinity");
                exit(1);
        }

        fn(arg);

        exit(0);
}

static unsigned long iterations;
static unsigned long iterations_prev;

static void sigalrm_handler(int junk)
{
        unsigned long i = iterations;

        printf("%ld\n", i - iterations_prev);
        iterations_prev = i;

        if (--timeout == 0)
                kill(0, SIGUSR1);

        alarm(1);
}

static void sigusr1_handler(int junk)
{
        exit(0);
}

struct actions {
        void (*setup)(int, int);
        void *(*thread1)(void *);
        void *(*thread2)(void *);
};

#define READ 0
#define WRITE 1

static int pipe_fd1[2];
static int pipe_fd2[2];

static void pipe_setup(int cpu1, int cpu2)
{
        if (pipe(pipe_fd1) || pipe(pipe_fd2))
                exit(1);
}

static void *pipe_thread1(void *arg)
{
        signal(SIGALRM, sigalrm_handler);
        alarm(1);

        while (1) {
                assert(read(pipe_fd1[READ], &c, 1) == 1);
                touch();

                assert(write(pipe_fd2[WRITE], &c, 1) == 1);
                touch();

                iterations += 2;
        }

        return NULL;
}

static void *pipe_thread2(void *arg)
{
        while (1) {
                assert(write(pipe_fd1[WRITE], &c, 1) == 1);
                touch();

                assert(read(pipe_fd2[READ], &c, 1) == 1);
                touch();
        }

        return NULL;
}

static struct actions pipe_actions = {
        .setup = pipe_setup,
        .thread1 = pipe_thread1,
        .thread2 = pipe_thread2,
};

static void yield_setup(int cpu1, int cpu2)
{
        if (cpu1 != cpu2) {
                fprintf(stderr, "Both threads must be on the same CPU for yield test\n");
                exit(1);
        }
}

static void *yield_thread1(void *arg)
{
        signal(SIGALRM, sigalrm_handler);
        alarm(1);

        while (1) {
                sched_yield();
                touch();

                iterations += 2;
        }

        return NULL;
}

static void *yield_thread2(void *arg)
{
        while (1) {
                sched_yield();
                touch();
        }

        return NULL;
}

static struct actions yield_actions = {
        .setup = yield_setup,
        .thread1 = yield_thread1,
        .thread2 = yield_thread2,
};

static long sys_futex(void *addr1, int op, int val1, struct timespec *timeout,
                      void *addr2, int val3)
{
        return syscall(SYS_futex, addr1, op, val1, timeout, addr2, val3);
}

static unsigned long cmpxchg(unsigned long *p, unsigned long expected,
                             unsigned long desired)
{
        unsigned long exp = expected;

        __atomic_compare_exchange_n(p, &exp, desired, 0,
                                    __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
        return exp;
}

static unsigned long xchg(unsigned long *p, unsigned long val)
{
        return __atomic_exchange_n(p, val, __ATOMIC_SEQ_CST);
}

static int mutex_lock(unsigned long *m)
{
        int c;

        c = cmpxchg(m, 0, 1);
        if (!c)
                return 0;

        if (c == 1)
                c = xchg(m, 2);

        while (c) {
                sys_futex(m, FUTEX_WAIT, 2, NULL, NULL, 0);
                c = xchg(m, 2);
        }

        return 0;
}

static int mutex_unlock(unsigned long *m)
{
        if (*m == 2)
                *m = 0;
        else if (xchg(m, 0) == 1)
                return 0;

        sys_futex(m, FUTEX_WAKE, 1, NULL, NULL, 0);

        return 0;
}

static unsigned long *m1, *m2;

static void futex_setup(int cpu1, int cpu2)
{
        int shmid;
        void *shmaddr;

        shmid = shmget(IPC_PRIVATE, getpagesize(), SHM_R | SHM_W);
        if (shmid < 0) {
                perror("shmget");
                exit(1);
        }

        shmaddr = shmat(shmid, NULL, 0);
        if (shmaddr == (char *)-1) {
                perror("shmat");
                shmctl(shmid, IPC_RMID, NULL);
                exit(1);
        }

        shmctl(shmid, IPC_RMID, NULL);

        m1 = shmaddr;
        m2 = shmaddr + sizeof(*m1);

        *m1 = 0;
        *m2 = 0;

        mutex_lock(m1);
        mutex_lock(m2);
}

static void *futex_thread1(void *arg)
{
        signal(SIGALRM, sigalrm_handler);
        alarm(1);

        while (1) {
                mutex_lock(m2);
                mutex_unlock(m1);

                iterations += 2;
        }

        return NULL;
}

static void *futex_thread2(void *arg)
{
        while (1) {
                mutex_unlock(m2);
                mutex_lock(m1);
        }

        return NULL;
}

static struct actions futex_actions = {
        .setup = futex_setup,
        .thread1 = futex_thread1,
        .thread2 = futex_thread2,
};

static int processes;

static struct option options[] = {
        { "test", required_argument, 0, 't' },
        { "process", no_argument, &processes, 1 },
        { "timeout", required_argument, 0, 's' },
        { "vdso", no_argument, &touch_vdso, 1 },
        { "no-fp", no_argument, &touch_fp, 0 },
#ifdef __powerpc__
        { "no-altivec", no_argument, &touch_altivec, 0 },
#endif
        { "no-vector", no_argument, &touch_vector, 0 },
        { 0, },
};

static void usage(void)
{
        fprintf(stderr, "Usage: context_switch2 <options> CPU1 CPU2\n\n");
        fprintf(stderr, "\t\t--test=X\tpipe, futex or yield (default)\n");
        fprintf(stderr, "\t\t--process\tUse processes (default threads)\n");
        fprintf(stderr, "\t\t--timeout=X\tDuration in seconds to run (default 30)\n");
        fprintf(stderr, "\t\t--vdso\t\ttouch VDSO\n");
        fprintf(stderr, "\t\t--no-fp\t\tDon't touch FP\n");
#ifdef __powerpc__
        fprintf(stderr, "\t\t--no-altivec\tDon't touch altivec\n");
#endif
        fprintf(stderr, "\t\t--no-vector\tDon't touch vector\n");
}

int main(int argc, char *argv[])
{
        signed char c;
        struct actions *actions = &yield_actions;
        int cpu1;
        int cpu2;
        static void (*start_fn)(void *(*fn)(void *), void *arg, unsigned long cpu);

        while (1) {
                int option_index = 0;

                c = getopt_long(argc, argv, "", options, &option_index);

                if (c == -1)
                        break;

                switch (c) {
                case 0:
                        if (options[option_index].flag != 0)
                                break;

                        usage();
                        exit(1);
                        break;

                case 't':
                        if (!strcmp(optarg, "pipe")) {
                                actions = &pipe_actions;
                        } else if (!strcmp(optarg, "yield")) {
                                actions = &yield_actions;
                        } else if (!strcmp(optarg, "futex")) {
                                actions = &futex_actions;
                        } else {
                                usage();
                                exit(1);
                        }
                        break;

                case 's':
                        timeout = atoi(optarg);
                        break;

                default:
                        usage();
                        exit(1);
                }
        }

        if (processes)
                start_fn = start_process_on;
        else
                start_fn = start_thread_on;

        if (((argc - optind) != 2)) {
                cpu1 = cpu2 = pick_online_cpu();
        } else {
                cpu1 = atoi(argv[optind++]);
                cpu2 = atoi(argv[optind++]);
        }

        printf("Using %s with ", processes ? "processes" : "threads");

        if (actions == &pipe_actions)
                printf("pipe");
        else if (actions == &yield_actions)
                printf("yield");
        else
                printf("futex");

        printf(" on cpus %d/%d touching FP:%s altivec:%s vector:%s vdso:%s\n",
               cpu1, cpu2, touch_fp ?  "yes" : "no", touch_altivec ? "yes" : "no",
               touch_vector ? "yes" : "no", touch_vdso ? "yes" : "no");

        /* Create a new process group so we can signal everyone for exit */
        setpgid(getpid(), getpid());

        signal(SIGUSR1, sigusr1_handler);

        actions->setup(cpu1, cpu2);

        start_fn(actions->thread1, NULL, cpu1);
        start_fn(actions->thread2, NULL, cpu2);

        while (1)
                sleep(3600);

        return 0;
}