libevent: fix race in the common case.

third_party/libevent/chromium.patch

Index: third_party/libevent/chromium.patch
diff --git a/third_party/libevent/chromium.patch b/third_party/libevent/chromium.patch
index 31bc327c4dc24eef0c6f37bd15168f7eb0da09d8..b8f355d3f74438a94092e2ad52a1c8fdae55bab6 100644
--- a/third_party/libevent/chromium.patch
+++ b/third_party/libevent/chromium.patch
@@ -81,3 +81,75 @@ index dcb0013..8b664b9 100644
  #ifdef _EVENT_HAVE_SYS_TIME_H
  #include <sys/time.h>
  #endif
+diff --git a/third_party/libevent/event.c b/third_party/libevent/event.c
+index 1253352..598a98f 100644
+--- a/third_party/libevent/event.c
++++ b/third_party/libevent/event.c
+@@ -107,7 +107,7 @@ static const struct eventop *eventops[] = {
+ /* Global state */
+ struct event_base *current_base = NULL;
+ extern struct event_base *evsignal_base;
+-static int use_monotonic;
++static int no_monotonic_clock = 0;
+ 
+ /* Prototypes */
+ static void	event_queue_insert(struct event_base *, struct event *, int);
+@@ -120,17 +120,6 @@ static int	timeout_next(struct event_base *, struct timeval **);
+ static void	timeout_process(struct event_base *);
+ static void	timeout_correct(struct event_base *, struct timeval *);
+ 
+-static void
+-detect_monotonic(void)
+-{
+-#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
+-	struct timespec	ts;
+-
+-	if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0)
+-		use_monotonic = 1;
+-#endif
+-}
+-
+ static int
+ gettime(struct event_base *base, struct timeval *tp)
+ {
+@@ -140,18 +129,18 @@ gettime(struct event_base *base, struct timeval *tp)
+ 	}
+ 
+ #if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
+-	if (use_monotonic) {
+-		struct timespec	ts;
+-
+-		if (clock_gettime(CLOCK_MONOTONIC, &ts) == -1)
+-			return (-1);
++	struct timespec	ts;
+ 
++	if (no_monotonic_clock == 0 &&
++	    clock_gettime(CLOCK_MONOTONIC, &ts) == 0) {
+ 		tp->tv_sec = ts.tv_sec;
+ 		tp->tv_usec = ts.tv_nsec / 1000;
+ 		return (0);
+ 	}
+ #endif
+ 
++	no_monotonic_clock = 1;
++
+ 	return (evutil_gettimeofday(tp, NULL));
+ }
+ 
+@@ -175,7 +164,6 @@ event_base_new(void)
+ 	if ((base = calloc(1, sizeof(struct event_base))) == NULL)
+ 		event_err(1, "%s: calloc", __func__);
+ 
+-	detect_monotonic();
+ 	gettime(base, &base->event_tv);
+ 	
+ 	min_heap_ctor(&base->timeheap);
+@@ -868,7 +856,7 @@ timeout_correct(struct event_base *base, struct timeval *tv)
+ 	unsigned int size;
+ 	struct timeval off;
+ 
+-	if (use_monotonic)
++	if (no_monotonic_clock == 0)
+ 		return;
+ 
+ 	/* Check if time is running backwards */