Mercurial > hg > nginx
view src/os/unix/ngx_thread_mutex.c @ 6422:768e287a6f36
Fixed sendfile in threads (or with aio preload) and subrequests.
If sendfile in threads is used, it is possible that multiple
subrequests will trigger multiple ngx_linux_sendfile_thread() calls,
as operations are only serialized in output chain based on r->aio,
that is, on subrequest level.
This resulted in "task #N already active" alerts, in particular, when
running proxy_store.t with "aio threads; sendfile on;".
Fix is to tolerate duplicate calls, with an additional safety check
that the file is the same as previously used.
The same problem also affects "aio on; sendfile on;" on FreeBSD
(previously known as "aio sendfile;"), where aio->preload_handler()
could be called multiple times due to similar reasons, resulting in
"second aio post" alerts. Fix is the same as well.
It is also believed that similar problems can arise if a filter
calls the next body filter multiple times for some reason. These are
mostly theoretical though.
author | Maxim Dounin <mdounin@mdounin.ru> |
---|---|
date | Thu, 03 Mar 2016 21:14:12 +0300 |
parents | 466bd63b63d1 |
children | e511e3d581bb |
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/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #include <ngx_config.h> #include <ngx_core.h> /* * All modern pthread mutex implementations try to acquire a lock * atomically in userland before going to sleep in kernel. Some * spins 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(). * 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. */ ngx_int_t ngx_thread_mutex_create(ngx_thread_mutex_t *mtx, ngx_log_t *log) { ngx_err_t err; pthread_mutexattr_t attr; err = pthread_mutexattr_init(&attr); if (err != 0) { ngx_log_error(NGX_LOG_EMERG, log, err, "pthread_mutexattr_init() failed"); return NGX_ERROR; } err = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK); if (err != 0) { ngx_log_error(NGX_LOG_EMERG, log, err, "pthread_mutexattr_settype" "(PTHREAD_MUTEX_ERRORCHECK) failed"); return NGX_ERROR; } err = pthread_mutex_init(mtx, &attr); if (err != 0) { ngx_log_error(NGX_LOG_EMERG, log, err, "pthread_mutex_init() failed"); return NGX_ERROR; } err = pthread_mutexattr_destroy(&attr); if (err != 0) { ngx_log_error(NGX_LOG_ALERT, log, err, "pthread_mutexattr_destroy() failed"); } ngx_log_debug1(NGX_LOG_DEBUG_CORE, log, 0, "pthread_mutex_init(%p)", mtx); return NGX_OK; } ngx_int_t ngx_thread_mutex_destroy(ngx_thread_mutex_t *mtx, ngx_log_t *log) { ngx_err_t err; err = pthread_mutex_destroy(mtx); if (err != 0) { ngx_log_error(NGX_LOG_ALERT, log, err, "pthread_mutex_destroy() failed"); return NGX_ERROR; } ngx_log_debug1(NGX_LOG_DEBUG_CORE, log, 0, "pthread_mutex_destroy(%p)", mtx); return NGX_OK; } ngx_int_t ngx_thread_mutex_lock(ngx_thread_mutex_t *mtx, ngx_log_t *log) { ngx_err_t err; ngx_log_debug1(NGX_LOG_DEBUG_CORE, log, 0, "pthread_mutex_lock(%p) enter", mtx); err = pthread_mutex_lock(mtx); if (err == 0) { return NGX_OK; } ngx_log_error(NGX_LOG_ALERT, log, err, "pthread_mutex_lock() failed"); return NGX_ERROR; } ngx_int_t ngx_thread_mutex_unlock(ngx_thread_mutex_t *mtx, ngx_log_t *log) { ngx_err_t err; err = pthread_mutex_unlock(mtx); #if 0 ngx_time_update(); #endif if (err == 0) { ngx_log_debug1(NGX_LOG_DEBUG_CORE, log, 0, "pthread_mutex_unlock(%p) exit", mtx); return NGX_OK; } ngx_log_error(NGX_LOG_ALERT, log, err, "pthread_mutex_unlock() failed"); return NGX_ERROR; }