From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Date: Sat, 12 Dec 2009 09:40:02 +0000 Subject: Re: RCU detected CPU 0 stall after panic on sparc64 Message-Id: <20091212.014002.173528710.davem@davemloft.net> List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: mroos@linux.ee Cc: linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org From: Meelis Roos Date: Sat, 12 Dec 2009 10:54:19 +0200 (EET) > I tried 2.6.32 git gaad3bf0 on a SMP sparc64 machine (Ultra Enterprise > 250). For some reason my disks were not found (not important in this > bugreport) and this resulted in panic (cannnot mount root). However, the > machine kept going and got the below messages (RCU detected CPU 0 stall > (t00 jiffies)) from timer interrupts. > > This seems to be like a bug in RCU vs panic. It's normal actually. A panic() just loops forever and the cpu never goes through an RCU grace period again as a result, and this triggers the debugging timer that detects this condition. Probably the panic() code should disable that assertion check. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761367AbZLLJj7 (ORCPT ); Sat, 12 Dec 2009 04:39:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760840AbZLLJj5 (ORCPT ); Sat, 12 Dec 2009 04:39:57 -0500 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:40672 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760669AbZLLJj4 (ORCPT ); Sat, 12 Dec 2009 04:39:56 -0500 Date: Sat, 12 Dec 2009 01:40:02 -0800 (PST) Message-Id: <20091212.014002.173528710.davem@davemloft.net> To: mroos@linux.ee Cc: linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org Subject: Re: RCU detected CPU 0 stall after panic on sparc64 From: David Miller In-Reply-To: References: X-Mailer: Mew version 6.3 on Emacs 23.1 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Meelis Roos Date: Sat, 12 Dec 2009 10:54:19 +0200 (EET) > I tried 2.6.32 git gaad3bf0 on a SMP sparc64 machine (Ultra Enterprise > 250). For some reason my disks were not found (not important in this > bugreport) and this resulted in panic (cannnot mount root). However, the > machine kept going and got the below messages (RCU detected CPU 0 stall > (t=1000 jiffies)) from timer interrupts. > > This seems to be like a bug in RCU vs panic. It's normal actually. A panic() just loops forever and the cpu never goes through an RCU grace period again as a result, and this triggers the debugging timer that detects this condition. Probably the panic() code should disable that assertion check.