Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756727Ab3EBJg6 (ORCPT ); Thu, 2 May 2013 05:36:58 -0400 Received: from mail-ia0-f178.google.com ([209.85.210.178]:36172 "EHLO mail-ia0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753927Ab3EBJg5 (ORCPT ); Thu, 2 May 2013 05:36:57 -0400 MIME-Version: 1.0 X-Originating-IP: [178.83.130.250] In-Reply-To: <1367485129-4423-1-git-send-email-imre.deak@intel.com> References: <1367485129-4423-1-git-send-email-imre.deak@intel.com> Date: Thu, 2 May 2013 11:36:56 +0200 Message-ID: Subject: Re: [PATCH] wait: fix false timeouts when using wait_event_timeout() From: Daniel Vetter To: Imre Deak Cc: "Paul E. McKenney" , David Howells , Dave Jones , Jens Axboe , Lukas Czerner , Linux Kernel Mailing List Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1443 Lines: 31 On Thu, May 2, 2013 at 10:58 AM, Imre Deak wrote: > Many callers of the wait_event_timeout() and > wait_event_interruptible_timeout() expect that the return value will be > positive if the specified condition becomes true before the timeout > elapses. However, at the moment this isn't guaranteed. If the wake-up > handler is delayed enough, the time remaining until timeout will be > calculated as 0 - and passed back as a return value - even if the > condition became true before the timeout has passed. > > Fix this by returning at least 1 if the condition becomes true. This > semantic is in line with what wait_for_condition_timeout() does; see > commit bb10ed09 - "sched: fix wait_for_completion_timeout() spurious > failure under heavy load". > > Signed-off-by: Imre Deak We have 3 instances of this bug in drm/i915. One case even where we switch between the interruptible and not interruptible wait_event_timeout variants, foolishly presuming they have the same semantics. I very much like this. Acked-by: Daniel Vetter -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/