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/*
* Copyright (C) Igor Sysoev
* Copyright (C) NGINX, Inc.
*/
#include <nxt_main.h>
/*
* All modern pthread mutex implementations try to acquire a lock atomically
* in userland before going to sleep in kernel. Some spins on SMP systems
* before the sleeping.
*
* In Solaris since version 8 all mutex types spin before sleeping.
* The default spin count is 1000. It can be overridden using
* _THREAD_ADAPTIVE_SPIN=100 environment variable.
*
* In MacOSX all mutex types spin to acquire a lock protecting a mutex's
* internals. If the mutex is busy, thread calls Mach semaphore_wait().
*
*
* PTHREAD_MUTEX_NORMAL lacks deadlock detection and is the fastest
* mutex type.
*
* Linux: No spinning. The internal name PTHREAD_MUTEX_TIMED_NP
* remains from the times when pthread_mutex_timedlock() was
* non-standard extension. Alias name: PTHREAD_MUTEX_FAST_NP.
* FreeBSD: No spinning.
*
*
* PTHREAD_MUTEX_ERRORCHECK is usually as fast as PTHREAD_MUTEX_NORMAL
* yet has lightweight deadlock detection.
*
* Linux: No spinning. The internal name: PTHREAD_MUTEX_ERRORCHECK_NP.
* FreeBSD: No spinning.
*
*
* PTHREAD_MUTEX_RECURSIVE allows recursive locking.
*
* Linux: No spinning. The internal name: PTHREAD_MUTEX_RECURSIVE_NP.
* FreeBSD: No spinning.
*
*
* PTHREAD_MUTEX_ADAPTIVE_NP spins on SMP systems before sleeping.
*
* Linux: No deadlock detection. Dynamically changes a spin count
* for each mutex from 10 to 100 based on spin count taken
* previously.
*
* FreeBSD: Deadlock detection. The default spin count is 2000.
* It can be overriden using LIBPTHREAD_SPINLOOPS environment
* variable or by pthread_mutex_setspinloops_np(). If a lock
* is still busy, sched_yield() can be called on both UP and
* SMP systems. The default yield loop count is zero, but it
* can be set by LIBPTHREAD_YIELDLOOPS environment variable or
* by pthread_mutex_setyieldloops_np(). sched_yield() moves
* a thread to the end of CPU scheduler run queue and this is
* cheaper than removing the thread from the queue and sleeping.
*
* Solaris: No PTHREAD_MUTEX_ADAPTIVE_NP .
* MacOSX: No PTHREAD_MUTEX_ADAPTIVE_NP.
*
*
* PTHREAD_MUTEX_ELISION_NP is a Linux extension to elide locks using
* Intel Restricted Transactional Memory. It is the most suitable for
* rwlock pattern access because it allows simultaneous reads without lock.
* Supported since glibc 2.18.
*
*
* PTHREAD_MUTEX_DEFAULT is default mutex type.
*
* Linux: PTHREAD_MUTEX_NORMAL.
* FreeBSD: PTHREAD_MUTEX_ERRORCHECK.
* Solaris: PTHREAD_MUTEX_NORMAL.
* MacOSX: PTHREAD_MUTEX_NORMAL.
*/
nxt_int_t
nxt_thread_mutex_create(nxt_thread_mutex_t *mtx)
{
nxt_err_t err;
pthread_mutexattr_t attr;
err = pthread_mutexattr_init(&attr);
if (err != 0) {
nxt_thread_log_emerg("pthread_mutexattr_init() failed %E", err);
return NXT_ERROR;
}
err = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK);
if (err != 0) {
nxt_thread_log_emerg("pthread_mutexattr_settype"
"(PTHREAD_MUTEX_ERRORCHECK) failed %E", err);
return NXT_ERROR;
}
err = pthread_mutex_init(mtx, &attr);
if (err != 0) {
nxt_thread_log_emerg("pthread_mutex_init() failed %E", err);
return NXT_ERROR;
}
err = pthread_mutexattr_destroy(&attr);
if (err != 0) {
nxt_thread_log_alert("pthread_mutexattr_destroy() failed %E", err);
}
nxt_thread_log_debug("pthread_mutex_init(%p)", mtx);
return NXT_OK;
}
void
nxt_thread_mutex_destroy(nxt_thread_mutex_t *mtx)
{
nxt_err_t err;
err = pthread_mutex_destroy(mtx);
if (nxt_slow_path(err != 0)) {
nxt_thread_log_alert("pthread_mutex_destroy() failed %E", err);
}
nxt_thread_log_debug("pthread_mutex_destroy(%p)", mtx);
}
nxt_int_t
nxt_thread_mutex_lock(nxt_thread_mutex_t *mtx)
{
nxt_err_t err;
nxt_thread_log_debug("pthread_mutex_lock(%p) enter", mtx);
err = pthread_mutex_lock(mtx);
if (nxt_fast_path(err == 0)) {
return NXT_OK;
}
nxt_thread_log_alert("pthread_mutex_lock() failed %E", err);
return NXT_ERROR;
}
nxt_bool_t
nxt_thread_mutex_trylock(nxt_thread_mutex_t *mtx)
{
nxt_err_t err;
nxt_thread_debug(thr);
nxt_log_debug(thr->log, "pthread_mutex_trylock(%p) enter", mtx);
err = pthread_mutex_trylock(mtx);
if (nxt_fast_path(err == 0)) {
return 1;
}
if (err == NXT_EBUSY) {
nxt_log_debug(thr->log, "pthread_mutex_trylock(%p) failed", mtx);
} else {
nxt_thread_log_alert("pthread_mutex_trylock() failed %E", err);
}
return 0;
}
nxt_int_t
nxt_thread_mutex_unlock(nxt_thread_mutex_t *mtx)
{
nxt_err_t err;
nxt_thread_t *thr;
err = pthread_mutex_unlock(mtx);
thr = nxt_thread();
nxt_thread_time_update(thr);
if (nxt_fast_path(err == 0)) {
nxt_log_debug(thr->log, "pthread_mutex_unlock(%p) exit", mtx);
return NXT_OK;
}
nxt_log_alert(thr->log, "pthread_mutex_unlock() failed %E", err);
return NXT_ERROR;
}
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