From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752086AbbASRsf (ORCPT ); Mon, 19 Jan 2015 12:48:35 -0500 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:38967 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751465AbbASRse (ORCPT ); Mon, 19 Jan 2015 12:48:34 -0500 Date: Mon, 19 Jan 2015 17:48:18 +0000 From: Russell King - ARM Linux To: Daniel Thompson Cc: Thomas Gleixner , Jason Cooper , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, patches@linaro.org, linaro-kernel@lists.linaro.org, John Stultz , Sumit Semwal , Dirk Behme , Daniel Drake , Dmitry Pervushin , Tim Sander , Stephen Boyd Subject: Re: [RFC PATCH 5/5] arm: perf: Use FIQ to handle PMU events. Message-ID: <20150119174818.GD26493@n2100.arm.linux.org.uk> References: <1421166931-14134-1-git-send-email-daniel.thompson@linaro.org> <1421166931-14134-6-git-send-email-daniel.thompson@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1421166931-14134-6-git-send-email-daniel.thompson@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 13, 2015 at 04:35:31PM +0000, Daniel Thompson wrote: > +/* > + * This handler is called *unconditionally* from the default NMI/FIQ > + * handler. The irq may not be anything to do with us so the main > + * job of this function is to figure out if the irq passed in is ours > + * or not. > + */ > +void cpu_pmu_handle_fiq(int irq) > +{ > + int cpu = smp_processor_id(); This can be either debug_smp_processor_id() or raw_smp_processor_id(). raw_smp_processor_id() is fine from FIQ contexts, as seems to be debug_smp_processor_id(), but only because we guarantee that irqs_disabled() in there will be true. > + > + if (irq != get_cpu_var(cpu_pmu_irqs)) > + return; get_cpu_var() needs put_cpu_var() to undo its effects. get_cpu_var() calls preempt_disable(), which calls into lockdep... I think we determined that was fine last time we went digging? put_cpu_var() would call preempt_enable() which I'd hope would be safe in FIQ/NMI contexts? > + > + (void)armpmu_dispatch_irq(irq, > + get_cpu_ptr(&cpu_pmu->hw_events->percpu_pmu)); Again, get_cpu_xxx() needs to be balanced with a put_cpu_xxx(). -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net. From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Mon, 19 Jan 2015 17:48:18 +0000 Subject: [RFC PATCH 5/5] arm: perf: Use FIQ to handle PMU events. In-Reply-To: <1421166931-14134-6-git-send-email-daniel.thompson@linaro.org> References: <1421166931-14134-1-git-send-email-daniel.thompson@linaro.org> <1421166931-14134-6-git-send-email-daniel.thompson@linaro.org> Message-ID: <20150119174818.GD26493@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Jan 13, 2015 at 04:35:31PM +0000, Daniel Thompson wrote: > +/* > + * This handler is called *unconditionally* from the default NMI/FIQ > + * handler. The irq may not be anything to do with us so the main > + * job of this function is to figure out if the irq passed in is ours > + * or not. > + */ > +void cpu_pmu_handle_fiq(int irq) > +{ > + int cpu = smp_processor_id(); This can be either debug_smp_processor_id() or raw_smp_processor_id(). raw_smp_processor_id() is fine from FIQ contexts, as seems to be debug_smp_processor_id(), but only because we guarantee that irqs_disabled() in there will be true. > + > + if (irq != get_cpu_var(cpu_pmu_irqs)) > + return; get_cpu_var() needs put_cpu_var() to undo its effects. get_cpu_var() calls preempt_disable(), which calls into lockdep... I think we determined that was fine last time we went digging? put_cpu_var() would call preempt_enable() which I'd hope would be safe in FIQ/NMI contexts? > + > + (void)armpmu_dispatch_irq(irq, > + get_cpu_ptr(&cpu_pmu->hw_events->percpu_pmu)); Again, get_cpu_xxx() needs to be balanced with a put_cpu_xxx(). -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net.