diff options
| author | Miklos Szeredi <mszeredi@redhat.com> | 2018-09-28 16:43:22 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-11-21 09:27:40 +0100 |
| commit | 2fe23468dae467043183e301829827c17f65f45f (patch) | |
| tree | 9076f3494c0d3ea89e6a53c9a2964217e984dab7 /fs | |
| parent | 8bb4354af373a8af395450acd298f25ddb79d93b (diff) | |
fuse: fix blocked_waitq wakeup
commit 908a572b80f6e9577b45e81b3dfe2e22111286b8 upstream.
Using waitqueue_active() is racy. Make sure we issue a wake_up()
unconditionally after storing into fc->blocked. After that it's okay to
optimize with waitqueue_active() since the first wake up provides the
necessary barrier for all waiters, not the just the woken one.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 3c18ef8117f0 ("fuse: optimize wake_up")
Cc: <stable@vger.kernel.org> # v3.10
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/fuse/dev.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 78225f1f1902..da31954e1a99 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -402,12 +402,19 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req) if (test_bit(FR_BACKGROUND, &req->flags)) { spin_lock(&fc->lock); clear_bit(FR_BACKGROUND, &req->flags); - if (fc->num_background == fc->max_background) + if (fc->num_background == fc->max_background) { fc->blocked = 0; - - /* Wake up next waiter, if any */ - if (!fc->blocked && waitqueue_active(&fc->blocked_waitq)) wake_up(&fc->blocked_waitq); + } else if (!fc->blocked) { + /* + * Wake up next waiter, if any. It's okay to use + * waitqueue_active(), as we've already synced up + * fc->blocked with waiters with the wake_up() call + * above. + */ + if (waitqueue_active(&fc->blocked_waitq)) + wake_up(&fc->blocked_waitq); + } if (fc->num_background == fc->congestion_threshold && fc->connected && fc->bdi_initialized) { |