File 0002-evwatch-fix-race-condition.patch of Package libevent

From 1eefbe38f6a7266e1489765317f4e89489856fc1 Mon Sep 17 00:00:00 2001
From: Dan Rosen <mergeconflict@google.com>
Date: Wed, 17 Apr 2019 15:44:59 -0400
Subject: [PATCH 2/2] evwatch: fix race condition

There was a race between event_base_loop and evwatch_new (adding a
prepare/check watcher while iterating over the watcher list). Only
release the mutex immediately before invoking each watcher callback,
and reacquire it immediately afterwards (same as is done for normal
event handlers).
---
 event.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/event.c b/event.c
index 5e41ae04..c6eb175c 100644
--- a/event.c
+++ b/event.c
@@ -2012,11 +2012,12 @@ event_base_loop(struct event_base *base, int flags)
 		event_queue_make_later_events_active(base);
 
 		/* Invoke prepare watchers before polling for events */
-		EVBASE_RELEASE_LOCK(base, th_base_lock);
 		prepare_info.timeout = tv_p;
-		TAILQ_FOREACH(watcher, &base->watchers[EVWATCH_PREPARE], next)
+		TAILQ_FOREACH(watcher, &base->watchers[EVWATCH_PREPARE], next) {
+			EVBASE_RELEASE_LOCK(base, th_base_lock);
 			(*watcher->callback.prepare)(watcher, &prepare_info, watcher->arg);
-		EVBASE_ACQUIRE_LOCK(base, th_base_lock);
+			EVBASE_ACQUIRE_LOCK(base, th_base_lock);
+		}
 
 		clear_time_cache(base);
 
@@ -2033,10 +2034,11 @@ event_base_loop(struct event_base *base, int flags)
 
 		/* Invoke check watchers after polling for events, and before
 		 * processing them */
-		EVBASE_RELEASE_LOCK(base, th_base_lock);
-		TAILQ_FOREACH(watcher, &base->watchers[EVWATCH_CHECK], next)
+		TAILQ_FOREACH(watcher, &base->watchers[EVWATCH_CHECK], next) {
+			EVBASE_RELEASE_LOCK(base, th_base_lock);
 			(*watcher->callback.check)(watcher, &check_info, watcher->arg);
-		EVBASE_ACQUIRE_LOCK(base, th_base_lock);
+			EVBASE_ACQUIRE_LOCK(base, th_base_lock);
+		}
 
 		timeout_process(base);
 
-- 
2.23.0