Mercurial > hg > nginx-quic
view src/http/ngx_http_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 |
line wrap: on
line source
/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #ifndef _NGX_HTTP_BUSY_LOCK_H_INCLUDED_ #define _NGX_HTTP_BUSY_LOCK_H_INCLUDED_ #include <ngx_config.h> #include <ngx_core.h> #include <ngx_event.h> #include <ngx_http.h> typedef struct { u_char *md5_mask; char *md5; int cacheable; int busy; int max_busy; int waiting; int max_waiting; time_t timeout; ngx_event_mutex_t *mutex; } ngx_http_busy_lock_t; typedef struct { time_t time; ngx_event_t *event; void (*event_handler)(ngx_event_t *ev); u_char *md5; int slot; } ngx_http_busy_lock_ctx_t; int ngx_http_busy_lock(ngx_http_busy_lock_t *bl, ngx_http_busy_lock_ctx_t *bc); int ngx_http_busy_lock_cacheable(ngx_http_busy_lock_t *bl, ngx_http_busy_lock_ctx_t *bc, int lock); void ngx_http_busy_unlock(ngx_http_busy_lock_t *bl, ngx_http_busy_lock_ctx_t *bc); char *ngx_http_set_busy_lock_slot(ngx_conf_t *cf, ngx_command_t *cmd, void *conf); #endif /* _NGX_HTTP_BUSY_LOCK_H_INCLUDED_ */