Events: protection from stale events in eventport and devpoll.

Stale write event may happen if read and write events was reported both,
and processing of the read event closed descriptor.

In practice this might result in "sendfilev() failed (134: ..." or
"writev() failed (134: ..." errors when switching to next upstream server.

See report here:
http://mailman.nginx.org/pipermail/nginx/2013-April/038421.html

2 files changed, 8 insertions, 2 deletions

diff --git a/src/event/modules/ngx_devpoll_module.c b/src/event/modules/ngx_devpoll_module.c
index d09b5bc07..5f78cd7d3 100644
--- a/src/event/modules/ngx_devpoll_module.c
+++ b/src/event/modules/ngx_devpoll_module.c
@@ -343,7 +343,7 @@ ngx_devpoll_process_events(ngx_cycle_t *cycle, ngx_msec_t timer,
     ngx_fd_t            fd;
     ngx_err_t           err;
     ngx_int_t           i;
-    ngx_uint_t          level;
+    ngx_uint_t          level, instance;
     ngx_event_t        *rev, *wev, **queue;
     ngx_connection_t   *c;
     struct pollfd       pfd;
@@ -510,7 +510,13 @@ ngx_devpoll_process_events(ngx_cycle_t *cycle, ngx_msec_t timer,
                 ngx_locked_post_event(rev, queue);
 
             } else {
+                instance = rev->instance;
+
                 rev->handler(rev);
+
+                if (c->fd == -1 || wev->instance != instance) {
+                    continue;
+                }
             }
         }
 
diff --git a/src/event/modules/ngx_eventport_module.c b/src/event/modules/ngx_eventport_module.c
index d6dcb0bed..5f9cf4e35 100644
--- a/src/event/modules/ngx_eventport_module.c
+++ b/src/event/modules/ngx_eventport_module.c
@@ -551,7 +551,7 @@ ngx_eventport_process_events(ngx_cycle_t *cycle, ngx_msec_t timer,
                 } else {
                     rev->handler(rev);
 
-                    if (ev->closed) {
+                    if (ev->closed || ev->instance != instance) {
                         continue;
                     }
                 }