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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>
This commit is contained in:
Soheil Hassas Yeganeh 2020-12-18 14:01:48 -08:00 committed by Linus Torvalds
parent 289caf5d8f
commit 2efdaf7660
1 changed files with 10 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
fs/eventpoll.c
View File

@ -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;