fixed a segment fault bug with upstream check module when check timeout is longer than the check interval

Author: yaoweibin

ngx_http_upstream_check_handler.c

@@ -335,10 +335,10 @@ ngx_http_check_begin_handler(ngx_event_t *event)
 
     ngx_add_timer(event, ucscf->check_interval/2);
 
-    /* This process is processing the event now. */
-    if (peer->shm->owner == ngx_pid) {
-        return;
-    }
+    /* This process is processing this peer now. */
+    if ((peer->shm->owner == ngx_pid) ||
+        (peer->pc.connection != NULL) ||
+        (peer->check_timeout_ev.timer_set)) {
 
     interval = ngx_current_msec - peer->shm->access_time;
     ngx_log_debug5(NGX_LOG_DEBUG_HTTP, event->log, 0,
@@ -1223,11 +1223,14 @@ ngx_http_check_clean_event(ngx_http_check_peer_t *peer)
 
     c = peer->pc.connection;
 
-    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
-                   "http check clean event: index:%ui, fd: %d",
-                   peer->index, c->fd);
+    if (c) {
+        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
+                "http check clean event: index:%ui, fd: %d",
+                peer->index, c->fd);
 
-    ngx_close_connection(c);
+        ngx_close_connection(c);
+        peer->pc.connection = NULL;
+    }
 
     if (peer->check_timeout_ev.timer_set) {
         ngx_del_timer(&peer->check_timeout_ev);
@@ -1314,7 +1317,10 @@ ngx_http_check_clear_all_events()
         /* Be careful, The shared memory may have been freed after reload */
         if (peer[i].check_timeout_ev.timer_set) {
             c = peer[i].pc.connection;
-            ngx_close_connection(c);
+            if (c) {
+                ngx_close_connection(c);
+                peer[i].pc.connection = NULL;
+            }
             ngx_del_timer(&peer[i].check_timeout_ev);
         }