Mercurial > hg > nginx-quic
view src/os/unix/ngx_thread_mutex.c @ 8867:5119c8150478
Fixed runtime handling of systems without EPOLLRDHUP support.
In 7583:efd71d49bde0 (nginx 1.17.5) along with introduction of the
ioctl(FIONREAD) support proper handling of systems without EPOLLRDHUP
support in the kernel (but with EPOLLRDHUP in headers) was broken.
Before the change, rev->available was never set to 0 unless
ngx_use_epoll_rdhup was also set (that is, runtime test for EPOLLRDHUP
introduced in 6536:f7849bfb6d21 succeeded). After the change,
rev->available might reach 0 on systems without runtime EPOLLRDHUP
support, stopping further reading in ngx_readv_chain() and ngx_unix_recv().
And, if EOF happened to be already reported along with the last event,
it is not reported again by epoll_wait(), leading to connection hangs
and timeouts on such systems.
This affects Linux kernels before 2.6.17 if nginx was compiled
with newer headers, and, more importantly, emulation layers, such as
DigitalOcean's App Platform's / gVisor's epoll emulation layer.
Fix is to explicitly check ngx_use_epoll_rdhup before the corresponding
rev->pending_eof tests in ngx_readv_chain() and ngx_unix_recv().
author | Marcus Ball <marcus.ball@live.com> |
---|---|
date | Mon, 30 May 2022 02:38:07 +0300 |
parents | 022ea0d17177 |
children |
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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 overridden 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"); } 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; } return NGX_OK; } ngx_int_t ngx_thread_mutex_lock(ngx_thread_mutex_t *mtx, ngx_log_t *log) { ngx_err_t err; 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) { return NGX_OK; } ngx_log_error(NGX_LOG_ALERT, log, err, "pthread_mutex_unlock() failed"); return NGX_ERROR; }