2013-08-17 15:06:40

by Eric Dumazet

Subject: [PATCH] epoll: add a reschedule point in ep_free()

From: Eric Dumazet <[email protected]>

ep_free() might iterate on a huge set of epitems and hold
cpu too long. Add two cond_resched() in order to yield cpu
to other tasks. This is safe as we only hold mutexes in
this function.

Signed-off-by: Eric Dumazet <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Theodore Ts'o <[email protected]>
---
Google-Bug-Id: 8940884

fs/eventpoll.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 9ad17b15..4ff595d 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -740,6 +740,7 @@ static void ep_free(struct eventpoll *ep)
epi = rb_entry(rbp, struct epitem, rbn);

ep_unregister_pollwait(ep, epi);
+ cond_resched();
}

/*
@@ -754,6 +755,7 @@ static void ep_free(struct eventpoll *ep)
while ((rbp = rb_first(&ep->rbr)) != NULL) {
epi = rb_entry(rbp, struct epitem, rbn);
ep_remove(ep, epi);
+ cond_resched();
}
mutex_unlock(&ep->mtx);

2013-08-27 23:33:08

by Eric Wong

Subject: Re: [PATCH] epoll: add a reschedule point in ep_free()

Eric Dumazet <[email protected]> wrote:
> From: Eric Dumazet <[email protected]>
>
> ep_free() might iterate on a huge set of epitems and hold
> cpu too long. Add two cond_resched() in order to yield cpu
> to other tasks. This is safe as we only hold mutexes in
> this function.
>
> Signed-off-by: Eric Dumazet <[email protected]>
> Cc: Al Viro <[email protected]>
> Cc: Theodore Ts'o <[email protected]>

Seems reasonable. This isn't a remotely hot path and f_op->release
runs in a workqueue nowadays (right?).

Acked-by: Eric Wong <[email protected]>