Mercurial > hg > nginx-quic
view src/event/ngx_event_busy_lock.h @ 5970:74edc0ccf27a
Core: fixed a race resulting in extra sem_post()'s.
The mtx->wait counter was not decremented if we were able to obtain the lock
right after incrementing it. This resulted in unneeded sem_post() calls,
eventually leading to EOVERFLOW errors being logged, "sem_post() failed
while wake shmtx (75: Value too large for defined data type)".
To close the race, mtx->wait is now decremented if we obtain the lock right
after incrementing it in ngx_shmtx_lock(). The result can become -1 if a
concurrent ngx_shmtx_unlock() decrements mtx->wait before the added code does.
However, that only leads to one extra iteration in the next call of
ngx_shmtx_lock().
author | Roman Arutyunyan <arut@nginx.com> |
---|---|
date | Wed, 04 Feb 2015 16:22:43 +0300 |
parents | d620f497c50f |
children | 457ec43dd8d5 |
line wrap: on
line source
/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #ifndef _NGX_EVENT_BUSY_LOCK_H_INCLUDED_ #define _NGX_EVENT_BUSY_LOCK_H_INCLUDED_ #include <ngx_config.h> #include <ngx_core.h> #include <ngx_event.h> typedef struct ngx_event_busy_lock_ctx_s ngx_event_busy_lock_ctx_t; struct ngx_event_busy_lock_ctx_s { ngx_event_t *event; ngx_event_handler_pt handler; void *data; ngx_msec_t timer; unsigned locked:1; unsigned waiting:1; unsigned cache_updated:1; char *md5; ngx_int_t slot; ngx_event_busy_lock_ctx_t *next; }; typedef struct { u_char *md5_mask; char *md5; ngx_uint_t cacheable; ngx_uint_t busy; ngx_uint_t max_busy; ngx_uint_t waiting; ngx_uint_t max_waiting; ngx_event_busy_lock_ctx_t *events; ngx_event_busy_lock_ctx_t *last; #if (NGX_THREADS) ngx_mutex_t *mutex; #endif } ngx_event_busy_lock_t; ngx_int_t ngx_event_busy_lock(ngx_event_busy_lock_t *bl, ngx_event_busy_lock_ctx_t *ctx); ngx_int_t ngx_event_busy_lock_cacheable(ngx_event_busy_lock_t *bl, ngx_event_busy_lock_ctx_t *ctx); void ngx_event_busy_unlock(ngx_event_busy_lock_t *bl, ngx_event_busy_lock_ctx_t *ctx); void ngx_event_busy_lock_cancel(ngx_event_busy_lock_t *bl, ngx_event_busy_lock_ctx_t *ctx); #endif /* _NGX_EVENT_BUSY_LOCK_H_INCLUDED_ */