From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 75175C43381 for ; Mon, 25 Mar 2019 22:09:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 459F42075E for ; Mon, 25 Mar 2019 22:09:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729681AbfCYWJN (ORCPT ); Mon, 25 Mar 2019 18:09:13 -0400 Received: from fieldses.org ([173.255.197.46]:55962 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728912AbfCYWJN (ORCPT ); Mon, 25 Mar 2019 18:09:13 -0400 Received: by fieldses.org (Postfix, from userid 2815) id 28D741CEE; Mon, 25 Mar 2019 18:09:13 -0400 (EDT) Date: Mon, 25 Mar 2019 18:09:13 -0400 From: "J. Bruce Fields" To: Jeff Layton Cc: linux-fsdevel@vger.kernel.org, neilb@suse.com, asn@redhat.com Subject: Re: [PATCH v3] locks: wake any locks blocked on request before deadlock check Message-ID: <20190325220913.GA22644@fieldses.org> References: <20190325123252.10211-1-jlayton@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190325123252.10211-1-jlayton@kernel.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Mar 25, 2019 at 08:32:52AM -0400, Jeff Layton wrote: > Andreas reported that he was seeing the tdbtorture test fail in some > cases with -EDEADLCK when it wasn't before. Some debugging showed that > deadlock detection was sometimes discovering the caller's lock request > itself in a dependency chain. > > While we remove the request from the blocked_lock_hash prior to > reattempting to acquire it, any locks that are blocked on that request > will still be present in the hash and will still have their fl_blocker > pointer set to the current request. This description is a lot easier for me to follow, thanks! > This causes posix_locks_deadlock to find a deadlock dependency chain > when it shouldn't, as a lock request cannot block itself. > > We are going to end up waking all of those blocked locks anyway when we > go to reinsert the request back into the blocked_lock_hash, so just do > it prior to checking for deadlocks. This ensures that any lock blocked > on the current request will no longer be part of any blocked request > chain. Looks right to me. --b. > > URL: https://bugzilla.kernel.org/show_bug.cgi?id=202975 > Fixes: 5946c4319ebb ("fs/locks: allow a lock request to block other requests.") > Cc: stable@vger.kernel.org > Reported-by: Andreas Schneider > Signed-off-by: Neil Brown > Signed-off-by: Jeff Layton > --- > fs/locks.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/fs/locks.c b/fs/locks.c > index eaa1cfaf73b0..71d0c6c2aac5 100644 > --- a/fs/locks.c > +++ b/fs/locks.c > @@ -1160,6 +1160,11 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request, > */ > error = -EDEADLK; > spin_lock(&blocked_lock_lock); > + /* > + * Ensure that we don't find any locks blocked on this > + * request during deadlock detection. > + */ > + __locks_wake_up_blocks(request); > if (likely(!posix_locks_deadlock(request, fl))) { > error = FILE_LOCK_DEFERRED; > __locks_insert_block(fl, request, > -- > 2.20.1