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Diffstat (limited to 'src/nxt_thread_time.c')
| -rw-r--r-- | src/nxt_thread_time.c | 468 |
1 files changed, 468 insertions, 0 deletions
diff --git a/src/nxt_thread_time.c b/src/nxt_thread_time.c new file mode 100644 index 00000000..f359a95e --- /dev/null +++ b/src/nxt_thread_time.c @@ -0,0 +1,468 @@ + +/* + * Copyright (C) Igor Sysoev + * Copyright (C) NGINX, Inc. + */ + +#include <nxt_main.h> + + +/* + * Each thread keeps several time representations in its thread local + * storage: + * the monotonic time in nanoseconds since unspecified point in the past, + * the real time in seconds and nanoseconds since the Epoch, + * the local time and GMT time structs, + * and various user-defined text representations of local and GMT times. + * + * The monotonic time is used mainly by engine timers and is updated after + * a kernel operation which can block for unpredictable duration like event + * polling. Besides getting the monotonic time is generally faster than + * getting the real time, so the monotonic time is also used for milestones + * to update cached real time seconds and, if debug log enabled, milliseconds. + * As a result, the cached real time is updated at most one time per second + * or millisecond respectively. If there is a signal event support or in + * multi-threaded mode, then the cached real time and local time structs + * are updated only on demand. In single-threaded mode without the signal + * event support the cached real and local time are updated synchronously + * with the monotonic time update. GMT time structs and text representations + * are always updated only on demand. + */ + + +#if (NXT_THREADS) +static void nxt_time_thread(void *data); +static void nxt_thread_time_shared(nxt_monotonic_time_t *now); + +static nxt_bool_t nxt_use_shared_time = 0; +static volatile nxt_monotonic_time_t nxt_shared_time; +#endif + +static void nxt_thread_realtime_update(nxt_thread_t *thr, + nxt_monotonic_time_t *now); +static u_char *nxt_thread_time_string_no_cache(nxt_thread_t *thr, + nxt_time_string_t *ts, u_char *buf); +static nxt_atomic_uint_t nxt_thread_time_string_slot(nxt_time_string_t *ts); +static nxt_time_string_cache_t *nxt_thread_time_string_cache(nxt_thread_t *thr, + nxt_atomic_uint_t slot); + + +static nxt_atomic_int_t nxt_gmtoff; + + +void +nxt_thread_time_update(nxt_thread_t *thr) +{ +#if (NXT_THREADS) + + if (nxt_use_shared_time) { + nxt_thread_time_shared(&thr->time.now); + + } else { + nxt_monotonic_time(&thr->time.now); + } + +#else + + nxt_monotonic_time(&thr->time.now); + + if (thr->time.signal >= 0) { + nxt_time_t s; + + /* + * Synchronous real time update: + * single-threaded mode without signal event support. + */ + + s = nxt_thread_time(thr); + + if (thr->time.signal == 0 && thr->time.last_localtime != s) { + /* Synchronous local time update in non-signal context. */ + + nxt_localtime(s, &thr->time.localtime); + thr->time.last_localtime = s; + + nxt_gmtoff = nxt_timezone(&thr->time.localtime); + } + } + +#endif +} + + +void +nxt_thread_time_free(nxt_thread_t *thr) +{ + nxt_uint_t i; + nxt_time_string_cache_t *tsc; + + tsc = thr->time.strings; + + if (tsc) { + thr->time.no_cache = 1; + + for (i = 0; i < thr->time.nstrings; i++) { + nxt_free(tsc[i].string.data); + } + + nxt_free(tsc); + thr->time.strings = NULL; + } +} + + +#if (NXT_THREADS) + +void +nxt_time_thread_start(nxt_msec_t interval) +{ + nxt_thread_link_t *link; + nxt_thread_handle_t handle; + + link = nxt_zalloc(sizeof(nxt_thread_link_t)); + + if (nxt_fast_path(link != NULL)) { + link->start = nxt_time_thread; + link->data = (void *) (uintptr_t) interval; + + (void) nxt_thread_create(&handle, link); + } +} + + +static void +nxt_time_thread(void *data) +{ + nxt_nsec_t interval, rest; + nxt_thread_t *thr; + nxt_monotonic_time_t now; + + interval = (uintptr_t) data; + interval *= 1000000; + + thr = nxt_thread(); + /* + * The time thread is never preempted by asynchronous signals, since + * the signals are processed synchronously by dedicated thread. + */ + thr->time.signal = -1; + + nxt_log_debug(thr->log, "time thread"); + + nxt_memzero(&now, sizeof(nxt_monotonic_time_t)); + + nxt_monotonic_time(&now); + nxt_thread_realtime_update(thr, &now); + + nxt_shared_time = now; + nxt_use_shared_time = 1; + + for ( ;; ) { + rest = 1000000000 - now.realtime.nsec; + + nxt_nanosleep(nxt_min(interval, rest)); + + nxt_monotonic_time(&now); + nxt_thread_realtime_update(thr, &now); + + nxt_shared_time = now; + +#if 0 + thr->time.now = now; + nxt_log_debug(thr->log, "time thread"); +#endif + +#if 0 + if (nxt_exiting) { + nxt_use_shared_time = 0; + return; + } +#endif + } +} + + +static void +nxt_thread_time_shared(nxt_monotonic_time_t *now) +{ + nxt_uint_t n; + nxt_time_t t; + nxt_nsec_t m, u; + + /* Lock-free thread time update. */ + + for ( ;; ) { + *now = nxt_shared_time; + + t = nxt_shared_time.realtime.sec; + n = nxt_shared_time.realtime.nsec; + m = nxt_shared_time.monotonic; + u = nxt_shared_time.update; + + if (now->realtime.sec == t && now->realtime.nsec == n + && now->monotonic == m && now->update == u) + { + return; + } + } +} + +#endif + + +nxt_time_t +nxt_thread_time(nxt_thread_t *thr) +{ + nxt_thread_realtime_update(thr, &thr->time.now); + + return thr->time.now.realtime.sec; +} + + +nxt_realtime_t * +nxt_thread_realtime(nxt_thread_t *thr) +{ + nxt_thread_realtime_update(thr, &thr->time.now); + + return &thr->time.now.realtime; +} + + +static void +nxt_thread_realtime_update(nxt_thread_t *thr, nxt_monotonic_time_t *now) +{ + nxt_nsec_t delta; + +#if (NXT_DEBUG) + + if (nxt_slow_path(thr->log->level == NXT_LOG_DEBUG || nxt_debug)) { + + if (now->monotonic >= now->update) { + nxt_realtime(&now->realtime); + + delta = 1000000 - now->realtime.nsec % 1000000; + now->update = now->monotonic + delta; + } + + return; + } + +#endif + + if (now->monotonic >= now->update) { + nxt_realtime(&now->realtime); + + delta = 1000000000 - now->realtime.nsec; + now->update = now->monotonic + delta; + } +} + + +u_char * +nxt_thread_time_string(nxt_thread_t *thr, nxt_time_string_t *ts, u_char *buf) +{ + u_char *p; + struct tm *tm; + nxt_time_t s; + nxt_bool_t update; + nxt_atomic_uint_t slot; + nxt_time_string_cache_t *tsc; + + if (nxt_slow_path(thr == NULL || thr->time.no_cache)) { + return nxt_thread_time_string_no_cache(thr, ts, buf); + } + + slot = nxt_thread_time_string_slot(ts); + + tsc = nxt_thread_time_string_cache(thr, slot); + if (tsc == NULL) { + return buf; + } + + if (thr->time.signal < 0) { + /* + * Lazy real time update: + * signal event support or multi-threaded mode. + */ + nxt_thread_realtime_update(thr, &thr->time.now); + } + + s = thr->time.now.realtime.sec; + + update = (s != tsc->last); + +#if (NXT_DEBUG) + + if (ts->msec == NXT_THREAD_TIME_MSEC + && (nxt_slow_path(thr->log->level == NXT_LOG_DEBUG || nxt_debug))) + { + nxt_msec_t ms; + + ms = thr->time.now.realtime.nsec / 1000000; + update |= (ms != tsc->last_msec); + tsc->last_msec = ms; + } + +#endif + + if (nxt_slow_path(update)) { + + if (ts->timezone == NXT_THREAD_TIME_LOCAL) { + + tm = &thr->time.localtime; + + if (nxt_slow_path(s != thr->time.last_localtime)) { + + if (thr->time.signal < 0) { + /* + * Lazy local time update: + * signal event support or multi-threaded mode. + */ + nxt_localtime(s, &thr->time.localtime); + thr->time.last_localtime = s; + + } else { + /* + * "thr->time.signal >= 0" means that a thread may be + * interrupted by a signal handler. Since localtime() + * cannot be safely called in a signal context, the + * thread's thr->time.localtime must be updated regularly + * by nxt_thread_time_update() in non-signal context. + * Stale timestamp means that nxt_thread_time_string() + * is being called in a signal context, so here is + * Async-Signal-Safe localtime() emulation using the + * latest cached GMT offset. + * + * The timestamp is not set here intentionally to update + * thr->time.localtime later in non-signal context. The + * real previously cached thr->localtime is used because + * Linux and Solaris strftime() depend on tm.tm_isdst + * and tm.tm_gmtoff fields. + */ + nxt_gmtime(s + nxt_timezone(tm), tm); + } + } + + } else { + tm = &thr->time.gmtime; + + if (nxt_slow_path(s != thr->time.last_gmtime)) { + nxt_gmtime(s, tm); + thr->time.last_gmtime = s; + } + + } + + p = tsc->string.data; + + if (nxt_slow_path(p == NULL)) { + + thr->time.no_cache = 1; + p = nxt_zalloc(ts->size); + thr->time.no_cache = 0; + + if (p == NULL) { + return buf; + } + + tsc->string.data = p; + } + + p = ts->handler(p, &thr->time.now.realtime, tm, ts->size, ts->format); + + tsc->string.len = p - tsc->string.data; + + if (nxt_slow_path(tsc->string.len == 0)) { + return buf; + } + + tsc->last = s; + } + + return nxt_cpymem(buf, tsc->string.data, tsc->string.len); +} + + +static u_char * +nxt_thread_time_string_no_cache(nxt_thread_t *thr, nxt_time_string_t *ts, + u_char *buf) +{ + struct tm tm; + nxt_realtime_t now; + + nxt_realtime(&now); + + if (ts->timezone == NXT_THREAD_TIME_LOCAL) { + + if (thr == NULL || thr->time.signal <= 0) { + /* Non-signal context */ + nxt_localtime(now.sec, &tm); + + } else { + nxt_gmtime(now.sec + nxt_gmtoff, &tm); + } + + } else { + nxt_gmtime(now.sec, &tm); + } + + return ts->handler(buf, &now, &tm, ts->size, ts->format); +} + + +static nxt_atomic_uint_t +nxt_thread_time_string_slot(nxt_time_string_t *ts) +{ + static nxt_atomic_t slot; + + while (nxt_slow_path((nxt_atomic_int_t) ts->slot < 0)) { + /* + * Atomic allocation of a slot number. + * -1 means an uninitialized slot, + * -2 is the initializing lock to assure the single value for the slot. + */ + if (nxt_atomic_cmp_set(&ts->slot, -1, -2)) { + ts->slot = nxt_atomic_fetch_add(&slot, 1); + + /* No "break" here since it adds only dispensable "jmp". */ + } + } + + return (nxt_atomic_uint_t) ts->slot; +} + + +static nxt_time_string_cache_t * +nxt_thread_time_string_cache(nxt_thread_t *thr, nxt_atomic_uint_t slot) +{ + size_t size; + nxt_atomic_uint_t i, nstrings; + nxt_time_string_cache_t *tsc; + + if (nxt_fast_path(slot < thr->time.nstrings)) { + tsc = &thr->time.strings[slot]; + nxt_prefetch(tsc->string.data); + return tsc; + } + + nstrings = slot + 1; + size = nstrings * sizeof(nxt_time_string_cache_t); + + thr->time.no_cache = 1; + tsc = nxt_realloc(thr->time.strings, size); + thr->time.no_cache = 0; + + if (tsc == NULL) { + return NULL; + } + + for (i = thr->time.nstrings; i < nstrings; i++) { + tsc[i].last = -1; + tsc[i].string.data = NULL; + } + + thr->time.strings = tsc; + thr->time.nstrings = nstrings; + + return &tsc[slot]; +} |