From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932987AbbIVLAB (ORCPT ); Tue, 22 Sep 2015 07:00:01 -0400 Received: from www.linutronix.de ([62.245.132.108]:40113 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932117AbbIVLAA (ORCPT ); Tue, 22 Sep 2015 07:00:00 -0400 Date: Tue, 22 Sep 2015 12:59:00 +0200 (CEST) From: Thomas Gleixner To: Daniel Thompson cc: Russell King , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, patches@linaro.org, linaro-kernel@lists.linaro.org, Hillf Danton Subject: Re: [PATCH v3] arm: Fix backtrace generation when IPI is masked In-Reply-To: <1442328005-13661-1-git-send-email-daniel.thompson@linaro.org> Message-ID: References: <1442222294-2756-1-git-send-email-daniel.thompson@linaro.org> <1442328005-13661-1-git-send-email-daniel.thompson@linaro.org> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 15 Sep 2015, Daniel Thompson wrote: > Currently on ARM when is triggered from an interrupt handler > (e.g. a SysRq issued using UART or kbd) the main CPU will wedge for ten > seconds with interrupts masked before issuing a backtrace for every CPU > except itself. > > The new backtrace code introduced by commit 96f0e00378d4 ("ARM: add > basic support for on-demand backtrace of other CPUs") does not work > correctly when run from an interrupt handler because IPI_CPU_BACKTRACE > is used to generate the backtrace on all CPUs but cannot preempt the > current calling context. > > This can be fixed by detecting that the calling context cannot be > preempted and issuing the backtrace directly in this case. Issuing > directly leaves us without any pt_regs to pass to nmi_cpu_backtrace() > so we also modify the generic code to call dump_stack() when its > argument is NULL. > > Signed-off-by: Daniel Thompson For the genric part. Acked-by: Thomas Gleixner