/*
 * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <config.h>
#include "timeval.h"
#include <errno.h>
#include <poll.h>
#include <pthread.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <unistd.h>
#include "coverage.h"
#include "dummy.h"
#include "dynamic-string.h"
#include "fatal-signal.h"
#include "hash.h"
#include "hmap.h"
#include "ovs-thread.h"
#include "signals.h"
#include "unixctl.h"
#include "util.h"
#include "vlog.h"

VLOG_DEFINE_THIS_MODULE(timeval);

struct clock {
    clockid_t id;               /* CLOCK_MONOTONIC or CLOCK_REALTIME. */
    struct ovs_rwlock rwlock;   /* Mutual exclusion for 'cache'. */

    /* Features for use by unit tests.  Protected by 'rwlock'. */
    struct timespec warp;       /* Offset added for unit tests. */
    bool stopped;               /* Disables real-time updates if true.  */

    /* Relevant only if CACHE_TIME is true. */
    volatile sig_atomic_t tick; /* Has the timer ticked?  Set by signal. */
    struct timespec cache;      /* Last time read from kernel. */
};

/* Our clocks. */
static struct clock monotonic_clock; /* CLOCK_MONOTONIC, if available. */
static struct clock wall_clock;      /* CLOCK_REALTIME. */

/* The monotonic time at which the time module was initialized. */
static long long int boot_time;

/* Monotonic time in milliseconds at which to die with SIGALRM (if not
 * LLONG_MAX). */
static long long int deadline = LLONG_MAX;

/* Monotonic time, in milliseconds, at which the last call to time_poll() woke
 * up. */
DEFINE_STATIC_PER_THREAD_DATA(long long int, last_wakeup, 0);

static void set_up_timer(void);
static void set_up_signal(int flags);
static void sigalrm_handler(int);
static void block_sigalrm(sigset_t *);
static void unblock_sigalrm(const sigset_t *);
static void log_poll_interval(long long int last_wakeup);
static struct rusage *get_recent_rusage(void);
static void refresh_rusage(void);
static void timespec_add(struct timespec *sum,
                         const struct timespec *a, const struct timespec *b);

static void
init_clock(struct clock *c, clockid_t id)
{
    memset(c, 0, sizeof *c);
    c->id = id;
    ovs_rwlock_init(&c->rwlock);
    xclock_gettime(c->id, &c->cache);
}

static void
do_init_time(void)
{
    struct timespec ts;

    coverage_init();

    init_clock(&monotonic_clock, (!clock_gettime(CLOCK_MONOTONIC, &ts)
                                  ? CLOCK_MONOTONIC
                                  : CLOCK_REALTIME));
    init_clock(&wall_clock, CLOCK_REALTIME);
    boot_time = timespec_to_msec(&monotonic_clock.cache);

    set_up_signal(SA_RESTART);
    set_up_timer();
}

/* Initializes the timetracking module, if not already initialized. */
static void
time_init(void)
{
    static pthread_once_t once = PTHREAD_ONCE_INIT;
    pthread_once(&once, do_init_time);
}

static void
set_up_signal(int flags)
{
    struct sigaction sa;

    memset(&sa, 0, sizeof sa);
    sa.sa_handler = sigalrm_handler;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = flags;
    xsigaction(SIGALRM, &sa, NULL);
}

static void
set_up_timer(void)
{
    static timer_t timer_id;    /* "static" to avoid apparent memory leak. */
    struct itimerspec itimer;

    if (!CACHE_TIME) {
        return;
    }

    if (timer_create(monotonic_clock.id, NULL, &timer_id)) {
        VLOG_FATAL("timer_create failed (%s)", ovs_strerror(errno));
    }

    itimer.it_interval.tv_sec = 0;
    itimer.it_interval.tv_nsec = TIME_UPDATE_INTERVAL * 1000 * 1000;
    itimer.it_value = itimer.it_interval;

    if (timer_settime(timer_id, 0, &itimer, NULL)) {
        VLOG_FATAL("timer_settime failed (%s)", ovs_strerror(errno));
    }
}

/* Set up the interval timer, to ensure that time advances even without calling
 * time_refresh().
 *
 * A child created with fork() does not inherit the parent's interval timer, so
 * this function needs to be called from the child after fork(). */
void
time_postfork(void)
{
    assert_single_threaded();
    time_init();
    set_up_timer();
}

/* Forces a refresh of the current time from the kernel.  It is not usually
 * necessary to call this function, since the time will be refreshed
 * automatically at least every TIME_UPDATE_INTERVAL milliseconds.  If
 * CACHE_TIME is false, we will always refresh the current time so this
 * function has no effect. */
void
time_refresh(void)
{
    monotonic_clock.tick = wall_clock.tick = true;
}

static void
time_timespec__(struct clock *c, struct timespec *ts)
{
    time_init();
    for (;;) {
        /* Use the cached time by preference, but fall through if there's been
         * a clock tick.  */
        ovs_rwlock_rdlock(&c->rwlock);
        if (c->stopped || !c->tick) {
            timespec_add(ts, &c->cache, &c->warp);
            ovs_rwlock_unlock(&c->rwlock);
            return;
        }
        ovs_rwlock_unlock(&c->rwlock);

        /* Refresh the cache. */
        ovs_rwlock_wrlock(&c->rwlock);
        if (c->tick) {
            c->tick = false;
            xclock_gettime(c->id, &c->cache);
        }
        ovs_rwlock_unlock(&c->rwlock);
    }
}

/* Stores a monotonic timer, accurate within TIME_UPDATE_INTERVAL ms, into
 * '*ts'. */
void
time_timespec(struct timespec *ts)
{
    time_timespec__(&monotonic_clock, ts);
}

/* Stores the current time, accurate within TIME_UPDATE_INTERVAL ms, into
 * '*ts'. */
void
time_wall_timespec(struct timespec *ts)
{
    time_timespec__(&wall_clock, ts);
}

static time_t
time_sec__(struct clock *c)
{
    struct timespec ts;

    time_timespec__(c, &ts);
    return ts.tv_sec;
}

/* Returns a monotonic timer, in seconds. */
time_t
time_now(void)
{
    return time_sec__(&monotonic_clock);
}

/* Returns the current time, in seconds. */
time_t
time_wall(void)
{
    return time_sec__(&wall_clock);
}

static long long int
time_msec__(struct clock *c)
{
    struct timespec ts;

    time_timespec__(c, &ts);
    return timespec_to_msec(&ts);
}

/* Returns a monotonic timer, in ms (within TIME_UPDATE_INTERVAL ms). */
long long int
time_msec(void)
{
    return time_msec__(&monotonic_clock);
}

/* Returns the current time, in ms (within TIME_UPDATE_INTERVAL ms). */
long long int
time_wall_msec(void)
{
    return time_msec__(&wall_clock);
}

/* Configures the program to die with SIGALRM 'secs' seconds from now, if
 * 'secs' is nonzero, or disables the feature if 'secs' is zero. */
void
time_alarm(unsigned int secs)
{
    long long int now;
    long long int msecs;

    assert_single_threaded();
    time_init();
    time_refresh();

    now = time_msec();
    msecs = secs * 1000LL;
    deadline = now < LLONG_MAX - msecs ? now + msecs : LLONG_MAX;
}

/* Like poll(), except:
 *
 *      - The timeout is specified as an absolute time, as defined by
 *        time_msec(), instead of a duration.
 *
 *      - On error, returns a negative error code (instead of setting errno).
 *
 *      - If interrupted by a signal, retries automatically until the original
 *        timeout is reached.  (Because of this property, this function will
 *        never return -EINTR.)
 *
 *      - As a side effect, refreshes the current time (like time_refresh()).
 *
 * Stores the number of milliseconds elapsed during poll in '*elapsed'. */
int
time_poll(struct pollfd *pollfds, int n_pollfds, long long int timeout_when,
          int *elapsed)
{
    long long int *last_wakeup = last_wakeup_get();
    long long int start;
    sigset_t oldsigs;
    bool blocked;
    int retval;

    time_init();
    time_refresh();
    if (*last_wakeup) {
        log_poll_interval(*last_wakeup);
    }
    coverage_clear();
    start = time_msec();
    blocked = false;

    timeout_when = MIN(timeout_when, deadline);

    for (;;) {
        long long int now = time_msec();
        int time_left;

        if (now >= timeout_when) {
            time_left = 0;
        } else if ((unsigned long long int) timeout_when - now > INT_MAX) {
            time_left = INT_MAX;
        } else {
            time_left = timeout_when - now;
        }

        retval = poll(pollfds, n_pollfds, time_left);
        if (retval < 0) {
            retval = -errno;
        }

        time_refresh();
        if (deadline <= time_msec()) {
            fatal_signal_handler(SIGALRM);
            if (retval < 0) {
                retval = 0;
            }
            break;
        }

        if (retval != -EINTR) {
            break;
        }

        if (!blocked && CACHE_TIME) {
            block_sigalrm(&oldsigs);
            blocked = true;
        }
    }
    if (blocked) {
        unblock_sigalrm(&oldsigs);
    }
    *last_wakeup = time_msec();
    refresh_rusage();
    *elapsed = *last_wakeup - start;
    return retval;
}

static void
sigalrm_handler(int sig_nr OVS_UNUSED)
{
    monotonic_clock.tick = wall_clock.tick = true;
}

static void
block_sigalrm(sigset_t *oldsigs)
{
    sigset_t sigalrm;
    sigemptyset(&sigalrm);
    sigaddset(&sigalrm, SIGALRM);
    xpthread_sigmask(SIG_BLOCK, &sigalrm, oldsigs);
}

static void
unblock_sigalrm(const sigset_t *oldsigs)
{
    xpthread_sigmask(SIG_SETMASK, oldsigs, NULL);
}

long long int
timespec_to_msec(const struct timespec *ts)
{
    return (long long int) ts->tv_sec * 1000 + ts->tv_nsec / (1000 * 1000);
}

long long int
timeval_to_msec(const struct timeval *tv)
{
    return (long long int) tv->tv_sec * 1000 + tv->tv_usec / 1000;
}

/* Returns the monotonic time at which the "time" module was initialized, in
 * milliseconds. */
long long int
time_boot_msec(void)
{
    time_init();
    return boot_time;
}

void
xgettimeofday(struct timeval *tv)
{
    if (gettimeofday(tv, NULL) == -1) {
        VLOG_FATAL("gettimeofday failed (%s)", ovs_strerror(errno));
    }
}

void
xclock_gettime(clock_t id, struct timespec *ts)
{
    if (clock_gettime(id, ts) == -1) {
        /* It seems like a bad idea to try to use vlog here because it is
         * likely to try to check the current time. */
        ovs_abort(errno, "xclock_gettime() failed");
    }
}

static long long int
timeval_diff_msec(const struct timeval *a, const struct timeval *b)
{
    return timeval_to_msec(a) - timeval_to_msec(b);
}

static void
timespec_add(struct timespec *sum,
             const struct timespec *a,
             const struct timespec *b)
{
    struct timespec tmp;

    tmp.tv_sec = a->tv_sec + b->tv_sec;
    tmp.tv_nsec = a->tv_nsec + b->tv_nsec;
    if (tmp.tv_nsec >= 1000 * 1000 * 1000) {
        tmp.tv_nsec -= 1000 * 1000 * 1000;
        tmp.tv_sec++;
    }

    *sum = tmp;
}

static void
log_poll_interval(long long int last_wakeup)
{
    long long int interval = time_msec() - last_wakeup;

    if (interval >= 1000
        && !monotonic_clock.warp.tv_sec
        && !monotonic_clock.warp.tv_nsec) {
        const struct rusage *last_rusage = get_recent_rusage();
        struct rusage rusage;

        getrusage(RUSAGE_SELF, &rusage);
        VLOG_WARN("Unreasonably long %lldms poll interval"
                  " (%lldms user, %lldms system)",
                  interval,
                  timeval_diff_msec(&rusage.ru_utime,
                                    &last_rusage->ru_utime),
                  timeval_diff_msec(&rusage.ru_stime,
                                    &last_rusage->ru_stime));
        if (rusage.ru_minflt > last_rusage->ru_minflt
            || rusage.ru_majflt > last_rusage->ru_majflt) {
            VLOG_WARN("faults: %ld minor, %ld major",
                      rusage.ru_minflt - last_rusage->ru_minflt,
                      rusage.ru_majflt - last_rusage->ru_majflt);
        }
        if (rusage.ru_inblock > last_rusage->ru_inblock
            || rusage.ru_oublock > last_rusage->ru_oublock) {
            VLOG_WARN("disk: %ld reads, %ld writes",
                      rusage.ru_inblock - last_rusage->ru_inblock,
                      rusage.ru_oublock - last_rusage->ru_oublock);
        }
        if (rusage.ru_nvcsw > last_rusage->ru_nvcsw
            || rusage.ru_nivcsw > last_rusage->ru_nivcsw) {
            VLOG_WARN("context switches: %ld voluntary, %ld involuntary",
                      rusage.ru_nvcsw - last_rusage->ru_nvcsw,
                      rusage.ru_nivcsw - last_rusage->ru_nivcsw);
        }
        coverage_log();
    }
}

/* CPU usage tracking. */

struct cpu_usage {
    long long int when;         /* Time that this sample was taken. */
    unsigned long long int cpu; /* Total user+system CPU usage when sampled. */
};

struct cpu_tracker {
    struct cpu_usage older;
    struct cpu_usage newer;
    int cpu_usage;

    struct rusage recent_rusage;
};
DEFINE_PER_THREAD_MALLOCED_DATA(struct cpu_tracker *, cpu_tracker_var);

static struct cpu_tracker *
get_cpu_tracker(void)
{
    struct cpu_tracker *t = cpu_tracker_var_get();
    if (!t) {
        t = xzalloc(sizeof *t);
        t->older.when = LLONG_MIN;
        t->newer.when = LLONG_MIN;
        cpu_tracker_var_set_unsafe(t);
    }
    return t;
}

static struct rusage *
get_recent_rusage(void)
{
    return &get_cpu_tracker()->recent_rusage;
}

static int
getrusage_thread(struct rusage *rusage OVS_UNUSED)
{
#ifdef RUSAGE_THREAD
    return getrusage(RUSAGE_THREAD, rusage);
#else
    errno = EINVAL;
    return -1;
#endif
}

static void
refresh_rusage(void)
{
    struct cpu_tracker *t = get_cpu_tracker();
    struct rusage *recent_rusage = &t->recent_rusage;

    if (!getrusage_thread(recent_rusage)) {
        long long int now = time_msec();
        if (now >= t->newer.when + 3 * 1000) {
            t->older = t->newer;
            t->newer.when = now;
            t->newer.cpu = (timeval_to_msec(&recent_rusage->ru_utime) +
                            timeval_to_msec(&recent_rusage->ru_stime));

            if (t->older.when != LLONG_MIN && t->newer.cpu > t->older.cpu) {
                unsigned int dividend = t->newer.cpu - t->older.cpu;
                unsigned int divisor = (t->newer.when - t->older.when) / 100;
                t->cpu_usage = divisor > 0 ? dividend / divisor : -1;
            } else {
                t->cpu_usage = -1;
            }
        }
    }
}

/* Returns an estimate of this process's CPU usage, as a percentage, over the
 * past few seconds of wall-clock time.  Returns -1 if no estimate is available
 * (which will happen if the process has not been running long enough to have
 * an estimate, and can happen for other reasons as well). */
int
get_cpu_usage(void)
{
    return get_cpu_tracker()->cpu_usage;
}

/* Unixctl interface. */

/* "time/stop" stops the monotonic time returned by e.g. time_msec() from
 * advancing, except due to later calls to "time/warp". */
static void
timeval_stop_cb(struct unixctl_conn *conn,
                 int argc OVS_UNUSED, const char *argv[] OVS_UNUSED,
                 void *aux OVS_UNUSED)
{
    ovs_rwlock_wrlock(&monotonic_clock.rwlock);
    monotonic_clock.stopped = true;
    ovs_rwlock_unlock(&monotonic_clock.rwlock);

    unixctl_command_reply(conn, NULL);
}

/* "time/warp MSECS" advances the current monotonic time by the specified
 * number of milliseconds.  Unless "time/stop" has also been executed, the
 * monotonic clock continues to tick forward at the normal rate afterward.
 *
 * Does not affect wall clock readings. */
static void
timeval_warp_cb(struct unixctl_conn *conn,
                int argc OVS_UNUSED, const char *argv[], void *aux OVS_UNUSED)
{
    struct timespec ts;
    int msecs;

    msecs = atoi(argv[1]);
    if (msecs <= 0) {
        unixctl_command_reply_error(conn, "invalid MSECS");
        return;
    }

    ts.tv_sec = msecs / 1000;
    ts.tv_nsec = (msecs % 1000) * 1000 * 1000;

    ovs_rwlock_wrlock(&monotonic_clock.rwlock);
    timespec_add(&monotonic_clock.warp, &monotonic_clock.warp, &ts);
    ovs_rwlock_unlock(&monotonic_clock.rwlock);

    unixctl_command_reply(conn, "warped");
}

void
timeval_dummy_register(void)
{
    unixctl_command_register("time/stop", "", 0, 0, timeval_stop_cb, NULL);
    unixctl_command_register("time/warp", "MSECS", 1, 1,
                             timeval_warp_cb, NULL);
}