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authorSoheil Hassas Yeganeh <soheil@google.com>2020-12-18 23:01:48 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2020-12-19 20:18:37 +0100
commit2efdaf7660c408d57721cc6dacb0167f866cb451 (patch)
treef408a18b19361393572b8a59525bf97826fd08f9 /fs/eventpoll.c
parentepoll: check for events when removing a timed out thread from the wait queue (diff)
downloadlinux-2efdaf7660c408d57721cc6dacb0167f866cb451.tar.xz
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epoll: simplify signal handling
Check signals before locking ep->lock, and immediately return -EINTR if there is any signal pending. This saves a few loads, stores, and branches from the hot path and simplifies the loop structure for follow up patches. Link: https://lkml.kernel.org/r/20201106231635.3528496-3-soheil.kdev@gmail.com Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Willem de Bruijn <willemb@google.com> Reviewed-by: Khazhismel Kumykov <khazhy@google.com> Cc: Guantao Liu <guantaol@google.com> 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.c20
1 files changed, 10 insertions, 10 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 935c66c809ba..4f460be723d0 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1733,7 +1733,7 @@ static inline struct timespec64 ep_set_mstimeout(long ms)
static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
int maxevents, long timeout)
{
- int res = 0, eavail, timed_out = 0;
+ int res, eavail, timed_out = 0;
u64 slack = 0;
wait_queue_entry_t wait;
ktime_t expires, *to = NULL;
@@ -1780,6 +1780,9 @@ fetch_events:
ep_reset_busy_poll_napi_id(ep);
do {
+ if (signal_pending(current))
+ return -EINTR;
+
/*
* Internally init_wait() uses autoremove_wake_function(),
* thus wait entry is removed from the wait queue on each
@@ -1809,15 +1812,12 @@ fetch_events:
* important.
*/
eavail = ep_events_available(ep);
- if (!eavail) {
- if (signal_pending(current))
- res = -EINTR;
- else
- __add_wait_queue_exclusive(&ep->wq, &wait);
- }
+ if (!eavail)
+ __add_wait_queue_exclusive(&ep->wq, &wait);
+
write_unlock_irq(&ep->lock);
- if (!eavail && !res)
+ if (!eavail)
timed_out = !schedule_hrtimeout_range(to, slack,
HRTIMER_MODE_ABS);
@@ -1853,14 +1853,14 @@ send_events:
* finding more events available and fetching
* repeatedly.
*/
- res = -EINTR;
+ return -EINTR;
}
/*
* Try to transfer events to user space. In case we get 0 events and
* there's still timeout left over, we go trying again in search of
* more luck.
*/
- if (!res && eavail &&
+ if (eavail &&
!(res = ep_send_events(ep, events, maxevents)) && !timed_out)
goto fetch_events;