From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932421AbaDVLyw (ORCPT ); Tue, 22 Apr 2014 07:54:52 -0400 Received: from www.linutronix.de ([62.245.132.108]:46879 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932156AbaDVLyt convert rfc822-to-8bit (ORCPT ); Tue, 22 Apr 2014 07:54:49 -0400 Date: Tue, 22 Apr 2014 13:54:39 +0200 From: Sebastian Andrzej Siewior To: Stanislav Meduna Cc: "linux-rt-users@vger.kernel.org" , Linux ARM Kernel , "linux-kernel@vger.kernel.org" , Steven Rostedt , Thomas Gleixner Subject: Re: BUG: spinlock trylock failure on UP, i.MX28 3.12.15-rt25 Message-ID: <20140422115439.GA20669@linutronix.de> References: <534C3606.7010206@meduna.org> <534C731F.1050406@meduna.org> <534DADF1.6060608@meduna.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: <534DADF1.6060608@meduna.org> X-Key-Id: 97C4700B X-Key-Fingerprint: 09E2 D1F3 9A3A FF13 C3D3 961C 0688 1C1E 97C4 700B User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Stanislav Meduna | 2014-04-16 00:08:49 [+0200]: >Hmm... how is it in the rt-case guaranteed that the timer interrupt >does not preempt someone trying to modify the timer? The run_local_timers >looks to have arrived via hardirq context. The spinlock in the tvec_base >is a normal one and spin_lock_irqsave does not disable interrupts >on rt, right? 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… Sebastian