From eeb72127cf4b86cb57f53e1f4702bbd1edd1a04a Mon Sep 17 00:00:00 2001 From: Maxim Dounin Date: Tue, 19 Apr 2016 17:18:28 +0300 Subject: [PATCH] Thread pools: memory barriers in task completion notifications. The ngx_thread_pool_done object isn't volatile, and at least some compilers assume that it is permitted to reorder modifications of volatile and non-volatile objects. Added appropriate ngx_memory_barrier() calls to make sure all modifications will happen before the lock is released. Reported by Mindaugas Rasiukevicius, http://mailman.nginx.org/pipermail/nginx-devel/2016-April/008160.html. --- src/core/ngx_thread_pool.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/core/ngx_thread_pool.c b/src/core/ngx_thread_pool.c index 03530851a..f3655aa0b 100644 --- a/src/core/ngx_thread_pool.c +++ b/src/core/ngx_thread_pool.c @@ -345,6 +345,8 @@ ngx_thread_pool_cycle(void *data) *ngx_thread_pool_done.last = task; ngx_thread_pool_done.last = &task->next; + ngx_memory_barrier(); + ngx_unlock(&ngx_thread_pool_done_lock); (void) ngx_notify(ngx_thread_pool_handler); @@ -366,6 +368,8 @@ ngx_thread_pool_handler(ngx_event_t *ev) ngx_thread_pool_done.first = NULL; ngx_thread_pool_done.last = &ngx_thread_pool_done.first; + ngx_memory_barrier(); + ngx_unlock(&ngx_thread_pool_done_lock); while (task) {