Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030229AbVLMVFl (ORCPT ); Tue, 13 Dec 2005 16:05:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030225AbVLMVFl (ORCPT ); Tue, 13 Dec 2005 16:05:41 -0500 Received: from ms-smtp-03.nyroc.rr.com ([24.24.2.57]:16100 "EHLO ms-smtp-03.nyroc.rr.com") by vger.kernel.org with ESMTP id S1030227AbVLMVFk (ORCPT ); Tue, 13 Dec 2005 16:05:40 -0500 Subject: Re: [ANNOUNCE] 2.6.15-rc5-hrt2 - hrtimers based high resolution patches From: Steven Rostedt To: tglx@linutronix.de Cc: john stultz , Ingo Molnar , Roman Zippel , LKML In-Reply-To: <1134385343.4205.72.camel@tglx.tec.linutronix.de> References: <1134385343.4205.72.camel@tglx.tec.linutronix.de> Content-Type: text/plain Date: Tue, 13 Dec 2005 16:05:27 -0500 Message-Id: <1134507927.18921.26.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2275 Lines: 59 Thomas and Ingo, I found a bug in 2.6.15-rc5-rt1 that was due to a race in the hrtimers code. This bug is most likely in the vanilla hrtimers code as well. I added a HRTIMER_RUNNING state because there's a moment in the run_hrtimer_queues that turns interrupts on and releases the base lock. In this time, a remove_hrtimer can be called while the state is still HRTIMER_PENDING_CALLBACK, but it has been removed off the list. The remove_hrtimer will then try to remove this again. Since I couldn't think of which state to use, I created the HRTIMER_RUNNING, and used that instead. I have a program (a simple jitter test) that, with out the patch, reliably crashes the 2.6.15-rc5-rt1 on a slow UP machine. With the patch, it runs solidly, so I know this is the reason for the crash. -- Steve Index: linux-2.6.15-rc5-rt1/kernel/hrtimer.c =================================================================== --- linux-2.6.15-rc5-rt1.orig/kernel/hrtimer.c 2005-12-13 15:51:52.000000000 -0500 +++ linux-2.6.15-rc5-rt1/kernel/hrtimer.c 2005-12-13 15:53:36.000000000 -0500 @@ -846,6 +846,7 @@ data = timer->data; set_curr_timer(base, timer); list_del(&timer->list); + timer->state = HRTIMER_RUNNING; spin_unlock_irq(&base->lock); /* @@ -904,6 +905,7 @@ data = timer->data; set_curr_timer(base, timer); __remove_hrtimer(timer, base); + timer->state = HRTIMER_RUNNING; spin_unlock_irq(&base->lock); /* Index: linux-2.6.15-rc5-rt1/include/linux/hrtimer.h =================================================================== --- linux-2.6.15-rc5-rt1.orig/include/linux/hrtimer.h 2005-12-13 15:51:40.000000000 -0500 +++ linux-2.6.15-rc5-rt1/include/linux/hrtimer.h 2005-12-13 15:55:21.000000000 -0500 @@ -41,6 +41,7 @@ enum hrtimer_state { HRTIMER_INACTIVE, /* Timer is inactive */ HRTIMER_EXPIRED, /* Timer is expired */ + HRTIMER_RUNNING, /* Timer is currently running */ HRTIMER_PENDING, /* Timer is pending */ HRTIMER_PENDING_CALLBACK, /* Timer is expired, callback pending */ }; - 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/