Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932494AbaDVNrG (ORCPT ); Tue, 22 Apr 2014 09:47:06 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.228]:27998 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756161AbaDVNrA convert rfc822-to-8bit (ORCPT ); Tue, 22 Apr 2014 09:47:00 -0400 Date: Tue, 22 Apr 2014 09:46:57 -0400 From: Steven Rostedt To: Sebastian Andrzej Siewior Cc: Stanislav Meduna , "linux-rt-users@vger.kernel.org" , Linux ARM Kernel , "linux-kernel@vger.kernel.org" , Thomas Gleixner , Peter Zijlstra Subject: Re: BUG: spinlock trylock failure on UP, i.MX28 3.12.15-rt25 Message-ID: <20140422094657.5b6ca1e2@gandalf.local.home> In-Reply-To: <20140422115439.GA20669@linutronix.de> References: <534C3606.7010206@meduna.org> <534C731F.1050406@meduna.org> <534DADF1.6060608@meduna.org> <20140422115439.GA20669@linutronix.de> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.22; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-RR-Connecting-IP: 107.14.168.118:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ added Peter ] On Tue, 22 Apr 2014 13:54:39 +0200 Sebastian Andrzej Siewior wrote: > this is, erm, harmless. We grab the timer lock via trylock in hardirq > context. If the lock is already taken then we fail to get it we go for > plan B. According to lockdep a trylock should not fail on UP. This is > true in general except for this timer case. I was thinking abour > disabling this lockdep check… trylock not failing on UP, can that be an issue? I mean, if a hardirq does a trylock to see if it can grab a lock that is not protected by disabling irqs, and will go to plan B if it fails, on UP, it will always get it. But the issue is still there. That would mean that a hardirq could have preempted a critical section and doing a trylock here would succeed when it really should have failed. -- Steve -- 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/