From: Nate Rosenblum <nater@maginatics.com>
Date: Tue, 5 Mar 2013 19:29:33 +0000 (-0800)
Subject: Double-check next timeout when adding events
X-Git-Tag: release-2.1.3-alpha~37
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=9443868d55a829cd66a2dce24daad84c5f1ca2ed;p=libevent

Double-check next timeout when adding events

When resuming the system from a suspended state, the ev_timeout field
of a scheduled timer event may be in the past. This leads to
unexpected behavior when scheduling a short-duration timer event
immediately after returning from suspension, because the new event
does not land on top of the timeout minheap and so the event loop
(blocked on a possibly long-duration timeout) is not notified.

This patch checks for this condition and, if it obtains, notifies the
event loop.
---

diff --git a/event.c b/event.c
index 51e34a99..9286c36f 100644
--- a/event.c
+++ b/event.c
@@ -2378,12 +2378,18 @@ event_add_nolock_(struct event *ev, const struct timeval *tv,
 				common_timeout_schedule(ctl, &now, ev);
 			}
 		} else {
+			struct event* top = NULL;
 			/* See if the earliest timeout is now earlier than it
 			 * was before: if so, we will need to tell the main
-			 * thread to wake up earlier than it would
-			 * otherwise. */
+			 * thread to wake up earlier than it would otherwise.
+			 * We double check the timeout of the top element to
+			 * handle time distortions due to system suspension.
+			 */
 			if (min_heap_elt_is_top_(ev))
 				notify = 1;
+			else if ((top = min_heap_top_(&base->timeheap)) != NULL &&
+					 evutil_timercmp(&top->ev_timeout, &now, <))
+				notify = 1;
 		}
 	}