epoll: epoll_wait() should not use timespec_add_ns()

commit 95aac7b ("epoll: make epoll_wait() use the hrtimer range feature") added a performance regression because it uses timespec_add_ns() with potential very large 'ns' values. [[email protected]: s/epoll_set_mstimeout/ep_set_mstimeout/, per Davide] Reported-by: Simon Kirby <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Cc: Shawn Bohrer <[email protected]> Acked-by: Davide Libenzi <[email protected]> Cc: <[email protected]> [2.6.37.x] Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
yshchan · Feb 3, 2011 · 0781b90 · 0781b90
1 parent 48db54e
commit 0781b90
Showing 1 changed file with 13 additions and 3 deletions.
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
@@ -1114,19 +1114,29 @@ static int ep_send_events(struct eventpoll *ep,
 	return ep_scan_ready_list(ep, ep_send_events_proc, &esed);
 }
 
+static inline struct timespec ep_set_mstimeout(long ms)
+{
+	struct timespec now, ts = {
+		.tv_sec = ms / MSEC_PER_SEC,
+		.tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC),
+	};
+
+	ktime_get_ts(&now);
+	return timespec_add_safe(now, ts);
+}
+
 static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 		   int maxevents, long timeout)
 {
 	int res, eavail, timed_out = 0;
 	unsigned long flags;
 	long slack;
 	wait_queue_t wait;
-	struct timespec end_time;
 	ktime_t expires, *to = NULL;
 
 	if (timeout > 0) {
-		ktime_get_ts(&end_time);
-		timespec_add_ns(&end_time, (u64)timeout * NSEC_PER_MSEC);
+		struct timespec end_time = ep_set_mstimeout(timeout);
+
 		slack = select_estimate_accuracy(&end_time);
 		to = &expires;
 		*to = timespec_to_ktime(end_time);