From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932763AbVITO1J (ORCPT ); Tue, 20 Sep 2005 10:27:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932764AbVITO1J (ORCPT ); Tue, 20 Sep 2005 10:27:09 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:18893 "EHLO mx3.mail.elte.hu") by vger.kernel.org with ESMTP id S932763AbVITO1H (ORCPT ); Tue, 20 Sep 2005 10:27:07 -0400 Date: Tue, 20 Sep 2005 16:27:53 +0200 From: Ingo Molnar To: Steven Rostedt Cc: LKML , Thomas Gleixner , Daniel Walker Subject: Re: [PATCH linux-2.6.13-rt14] Priority inversion bug Message-ID: <20050920142753.GA6132@elte.hu> References: <1127162309.5097.15.camel@localhost.localdomain> <20050920133706.GA4855@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=disabled SpamAssassin version=3.0.3 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Steven Rostedt wrote: > On Tue, 20 Sep 2005, Ingo Molnar wrote: > > thanks - added it to my tree. I'm wondering why it never showed up in > > practice? > > How do we know if it hasn't? It wouldn't bug, you may just have a > longer latency on the higher priority process than what should be. It > did happen on my kernel, and the way I found that it did, was that I > had a test in the passing of ownership to make sure that the one that > got the lock is indeed the highest priority process. Without this > check, we probably would never know. 'showed up' as in 'clearly incorrect scheduling shown in latency trace'. It's probably the complex locking scenario that never made it trigger in the simpler tests that e.g. rtc_wakeup or other latency testers do. Ingo