From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752212AbdLFQnx (ORCPT ); Wed, 6 Dec 2017 11:43:53 -0500 Received: from mail-wm0-f54.google.com ([74.125.82.54]:43253 "EHLO mail-wm0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752715AbdLFQns (ORCPT ); Wed, 6 Dec 2017 11:43:48 -0500 X-Google-Smtp-Source: AGs4zMZs+Z99sJswgHi3DzkPyfEYgwJ+VtsWPJUchQlTcoLyHERlfFzFM5zTEOi4eyONJEJARXkKcQ== Date: Wed, 6 Dec 2017 17:43:44 +0100 From: Ingo Molnar To: Linus Torvalds Cc: Omar Sandoval , Linux Kernel Mailing List , Jens Axboe Subject: Re: add_wait_queue() (unintentional?) behavior change in v4.13 Message-ID: <20171206164344.iy57cvwgbsqhtwwz@gmail.com> References: <20171130005828.GA15628@vader> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Linus Torvalds wrote: > On Wed, Nov 29, 2017 at 4:58 PM, Omar Sandoval wrote: > > > > Note the change from __add_wait_queue() to > > __add_wait_queue_entry_tail(). I'm assuming this was a typo since the > > commit message doesn't mention any functional changes. This patch > > restores the old behavior: > > [...] > > I didn't go through and audit callers of add_wait_queue(), but from a > > quick code read this makes it so that non-exclusive waiters will not be > > woken up if they are behind enough exclusive waiters, and I bet that'll > > cause some bugs. > > This sounds right to me. > > Ingo? Yeah, it's indeed unintended and it's a bug - I have applied the fix and will get it to you ASAP. Thanks, Ingo