Mercurial > hg > nginx
view src/event/ngx_event_timer.c @ 3755:76e3a93821b1
fix race condition if during reconfiguration two cache managers try
to delete old inactive entries: one of them removes a entry just locked by
other manager from the queue and the rbtree as long inactive entry,
causes the latter manager to segfault leaving cache mutex locked,
the bug has been introduced in r3727
author | Igor Sysoev <igor@sysoev.ru> |
---|---|
date | Thu, 02 Sep 2010 14:31:47 +0000 |
parents | 4fc402c3ec73 |
children | 59b99f217c6d |
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/* * Copyright (C) Igor Sysoev */ #include <ngx_config.h> #include <ngx_core.h> #include <ngx_event.h> #if (NGX_THREADS) ngx_mutex_t *ngx_event_timer_mutex; #endif ngx_thread_volatile ngx_rbtree_t ngx_event_timer_rbtree; static ngx_rbtree_node_t ngx_event_timer_sentinel; /* * the event timer rbtree may contain the duplicate keys, however, * it should not be a problem, because we use the rbtree to find * a minimum timer value only */ ngx_int_t ngx_event_timer_init(ngx_log_t *log) { ngx_rbtree_init(&ngx_event_timer_rbtree, &ngx_event_timer_sentinel, ngx_rbtree_insert_timer_value); #if (NGX_THREADS) if (ngx_event_timer_mutex) { ngx_event_timer_mutex->log = log; return NGX_OK; } ngx_event_timer_mutex = ngx_mutex_init(log, 0); if (ngx_event_timer_mutex == NULL) { return NGX_ERROR; } #endif return NGX_OK; } ngx_msec_t ngx_event_find_timer(void) { ngx_msec_int_t timer; ngx_rbtree_node_t *node, *root, *sentinel; if (ngx_event_timer_rbtree.root == &ngx_event_timer_sentinel) { return NGX_TIMER_INFINITE; } ngx_mutex_lock(ngx_event_timer_mutex); root = ngx_event_timer_rbtree.root; sentinel = ngx_event_timer_rbtree.sentinel; node = ngx_rbtree_min(root, sentinel); ngx_mutex_unlock(ngx_event_timer_mutex); timer = (ngx_msec_int_t) node->key - (ngx_msec_int_t) ngx_current_msec; return (ngx_msec_t) (timer > 0 ? timer : 0); } void ngx_event_expire_timers(void) { ngx_event_t *ev; ngx_rbtree_node_t *node, *root, *sentinel; sentinel = ngx_event_timer_rbtree.sentinel; for ( ;; ) { ngx_mutex_lock(ngx_event_timer_mutex); root = ngx_event_timer_rbtree.root; if (root == sentinel) { return; } node = ngx_rbtree_min(root, sentinel); /* node->key <= ngx_current_time */ if ((ngx_msec_int_t) node->key - (ngx_msec_int_t) ngx_current_msec <= 0) { ev = (ngx_event_t *) ((char *) node - offsetof(ngx_event_t, timer)); #if (NGX_THREADS) if (ngx_threaded && ngx_trylock(ev->lock) == 0) { /* * We can not change the timer of the event that is been * handling by another thread. And we can not easy walk * the rbtree to find a next expired timer so we exit the loop. * However it should be rare case when the event that is * been handling has expired timer. */ ngx_log_debug1(NGX_LOG_DEBUG_EVENT, ev->log, 0, "event %p is busy in expire timers", ev); break; } #endif ngx_log_debug2(NGX_LOG_DEBUG_EVENT, ev->log, 0, "event timer del: %d: %M", ngx_event_ident(ev->data), ev->timer.key); ngx_rbtree_delete(&ngx_event_timer_rbtree, &ev->timer); ngx_mutex_unlock(ngx_event_timer_mutex); #if (NGX_DEBUG) ev->timer.left = NULL; ev->timer.right = NULL; ev->timer.parent = NULL; #endif ev->timer_set = 0; #if (NGX_THREADS) if (ngx_threaded) { ev->posted_timedout = 1; ngx_post_event(ev, &ngx_posted_events); ngx_unlock(ev->lock); continue; } #endif ev->timedout = 1; ev->handler(ev); continue; } break; } ngx_mutex_unlock(ngx_event_timer_mutex); }