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| author | Miklos Szeredi <mszeredi@redhat.com> | 2018-09-28 16:43:22 +0200 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2018-09-28 16:43:22 +0200 |
| commit | 908a572b80f6e9577b45e81b3dfe2e22111286b8 (patch) | |
| tree | 9752e255244d3e6314f471fdc15f4491c1dc8939 /fs/fuse/dev.c | |
| parent | 4c316f2f3ff315cb48efb7435621e5bfb81df96d (diff) | |
| download | lwn-908a572b80f6e9577b45e81b3dfe2e22111286b8.tar.gz lwn-908a572b80f6e9577b45e81b3dfe2e22111286b8.zip | |
fuse: fix blocked_waitq wakeup
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
Diffstat (limited to 'fs/fuse/dev.c')
| -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 34976b42f3e1..51eb602a435b 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -391,12 +391,19 @@ 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->sb) { clear_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC); |