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authorShawn Bohrer <shawn.bohrer@gmail.com>2010-10-27 15:34:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-27 18:03:18 -0700
commit95aac7b1cd224f568fb83937044cd303ff11b029 (patch)
tree24c08cfe031ecc0549cf3f7900e992a27044c4ad /fs/eventpoll.c
parent231f3d393f63f6e3b505afa179999bba491d0f08 (diff)
downloadlinux-linaro-stable-95aac7b1cd224f568fb83937044cd303ff11b029.tar.gz
epoll: make epoll_wait() use the hrtimer range feature
This make epoll use hrtimers for the timeout value which prevents epoll_wait() from timing out up to a millisecond early. This mirrors the behavior of select() and poll(). Signed-off-by: Shawn Bohrer <shawn.bohrer@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Acked-by: Davide Libenzi <davidel@xmailserver.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/eventpoll.c')
-rw-r--r--fs/eventpoll.c35
1 files changed, 19 insertions, 16 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 256bb7bb102a..8cf07242067d 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -77,9 +77,6 @@
/* Maximum number of nesting allowed inside epoll sets */
#define EP_MAX_NESTS 4
-/* Maximum msec timeout value storeable in a long int */
-#define EP_MAX_MSTIMEO min(1000ULL * MAX_SCHEDULE_TIMEOUT / HZ, (LONG_MAX - 999ULL) / HZ)
-
#define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
#define EP_UNACTIVE_PTR ((void *) -1L)
@@ -1117,18 +1114,22 @@ static int ep_send_events(struct eventpoll *ep,
static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
int maxevents, long timeout)
{
- int res, eavail;
+ int res, eavail, timed_out = 0;
unsigned long flags;
- long jtimeout;
+ long slack;
wait_queue_t wait;
-
- /*
- * Calculate the timeout by checking for the "infinite" value (-1)
- * and the overflow condition. The passed timeout is in milliseconds,
- * that why (t * HZ) / 1000.
- */
- jtimeout = (timeout < 0 || timeout >= EP_MAX_MSTIMEO) ?
- MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000;
+ 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);
+ slack = select_estimate_accuracy(&end_time);
+ to = &expires;
+ *to = timespec_to_ktime(end_time);
+ } else if (timeout == 0) {
+ timed_out = 1;
+ }
retry:
spin_lock_irqsave(&ep->lock, flags);
@@ -1150,7 +1151,7 @@ retry:
* to TASK_INTERRUPTIBLE before doing the checks.
*/
set_current_state(TASK_INTERRUPTIBLE);
- if (!list_empty(&ep->rdllist) || !jtimeout)
+ if (!list_empty(&ep->rdllist) || timed_out)
break;
if (signal_pending(current)) {
res = -EINTR;
@@ -1158,7 +1159,9 @@ retry:
}
spin_unlock_irqrestore(&ep->lock, flags);
- jtimeout = schedule_timeout(jtimeout);
+ if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
+ timed_out = 1;
+
spin_lock_irqsave(&ep->lock, flags);
}
__remove_wait_queue(&ep->wq, &wait);
@@ -1176,7 +1179,7 @@ retry:
* more luck.
*/
if (!res && eavail &&
- !(res = ep_send_events(ep, events, maxevents)) && jtimeout)
+ !(res = ep_send_events(ep, events, maxevents)) && !timed_out)
goto retry;
return res;