From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out5-smtp.messagingengine.com ([66.111.4.29]:47131 "EHLO out5-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725895AbeKOLMN (ORCPT ); Thu, 15 Nov 2018 06:12:13 -0500 Subject: FAILED: patch "[PATCH] fuse: fix blocked_waitq wakeup" failed to apply to 3.18-stable tree To: mszeredi@redhat.com, stable@vger.kernel.org Cc: From: Date: Wed, 14 Nov 2018 17:06:25 -0800 Message-ID: <154224398558147@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: The patch below does not apply to the 3.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >>From 908a572b80f6e9577b45e81b3dfe2e22111286b8 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Fri, 28 Sep 2018 16:43:22 +0200 Subject: [PATCH] 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 Fixes: 3c18ef8117f0 ("fuse: optimize wake_up") Cc: # v3.10 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);