Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755322AbaDNWiB (ORCPT ); Mon, 14 Apr 2014 18:38:01 -0400 Received: from mail-wi0-f179.google.com ([209.85.212.179]:53777 "EHLO mail-wi0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754255AbaDNWh7 (ORCPT ); Mon, 14 Apr 2014 18:37:59 -0400 MIME-Version: 1.0 In-Reply-To: <20140414105314.GB3530@arm.com> References: <1395178858-27343-1-git-send-email-sebastian.capella@linaro.org> <1395178858-27343-2-git-send-email-sebastian.capella@linaro.org> <20140414105314.GB3530@arm.com> Date: Mon, 14 Apr 2014 15:37:58 -0700 Message-ID: Subject: Re: [PATCH v9 1/2] ARM: avoid tracers in soft_restart From: Sebastian Capella To: Will Deacon Cc: "linux-kernel@vger.kernel.org" , "linux-pm@vger.kernel.org" , "linaro-kernel@lists.linaro.org" , "linux-arm-kernel@lists.infradead.org" , Russell King , Andrew Morton , Robin Holt , Thomas Gleixner , Konstantin Khlebnikov , Steven Capper , Stephen Warren , Tejun Heo Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Will, On 14 April 2014 03:53, Will Deacon wrote: > On Tue, Mar 18, 2014 at 09:40:57PM +0000, Sebastian Capella wrote: >> Use of tracers in local_irq_disable is causes abort loops when called >> with irqs disabled using a temporary stack. Replace local_irq_disable >> with raw_local_irq_disable instead to avoid tracers. > > Do you have any more information about these aborts? At the time we call > local_irq_disable, the stack is still intact, so if the issue is simply > related to having any tracers active at the call_with_stack invocation, we'd > be better off disabling tracing here altogether. This is specifically for when soft_restart is called in the hibernation path with tracers enabled. At that point, we've already switched to a temporary stack, and when we call local_irq_disable, we'll see this: In the local_irq_disable, it ends up calling trace_hardirqs_off (CONFIG_TRACE_IRQFLAGS_SUPPORT is enabled), which calls trace_hardirqs_off_caller which checks lockdep_recursion in the current task, but we've switched to a temporary stack with the call_with_stack, and get_current is returning NULL. This triggers a data abort, which calls trace_hardirqs_off again and so on. We originally had a patch which added a soft restart called soft_restart_noirq which avoided the irq disable. You can see the discussion here: https://patchwork.kernel.org/patch/3677591/ Thanks! Sebastian -- 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/