Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756310AbaFXUfl (ORCPT ); Tue, 24 Jun 2014 16:35:41 -0400 Received: from avon.wwwdotorg.org ([70.85.31.133]:34514 "EHLO avon.wwwdotorg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751370AbaFXUfj (ORCPT ); Tue, 24 Jun 2014 16:35:39 -0400 Message-ID: <53A9E117.4010704@wwwdotorg.org> Date: Tue, 24 Jun 2014 14:35:35 -0600 From: Stephen Warren User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Frederic Weisbecker CC: LKML , Andrew Morton , Eric Dumazet , Ingo Molnar , Kevin Hilman , "Paul E. McKenney" , Peter Zijlstra , Thomas Gleixner , Viresh Kumar , "Srivatsa S. Bhat" , "linux-next@vger.kernel.org" Subject: Re: [PATCH 2/6] irq_work: Implement remote queueing References: <1402413309-3415-1-git-send-email-fweisbec@gmail.com> <1402413309-3415-3-git-send-email-fweisbec@gmail.com> <53A9E0A5.5040402@wwwdotorg.org> In-Reply-To: <53A9E0A5.5040402@wwwdotorg.org> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/24/2014 02:33 PM, Stephen Warren wrote: > On 06/10/2014 09:15 AM, Frederic Weisbecker wrote: >> irq work currently only supports local callbacks. However its code >> is mostly ready to run remote callbacks and we have some potential user. >> >> The full nohz subsystem currently open codes its own remote irq work >> on top of the scheduler ipi when it wants a CPU to reevaluate its next >> tick. However this ad hoc solution bloats the scheduler IPI. >> >> Lets just extend the irq work subsystem to support remote queuing on top >> of the generic SMP IPI to handle this kind of user. This shouldn't add >> noticeable overhead. > > I'm running next-20140624 on an ARM system, and this patch causes CPU > hot(un)plug to Oops for me; the following fires: > > void irq_work_run(void) > { > BUG_ON(!in_irq()); > > I found that Linus's master (8b8f5d971584 "Merge tag 'compress-3.16-rc3' > of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core") > works fine. I found that this commit inside the tip(?) tree works fine > (478850160636 "irq_work: Implement remote queueing"). However, if I > merge the two together, I hit that BUG_ON. I forgot to mention that the conflicting commit from Linus' tree is 8d056c48e486 "CPU hotplug, smp: flush any pending IPI callbacks before CPU offline". > I think the issue is: > > This commit adds a call from > generic_smp_call_function_single_interrupt() to irq_work_run(). > > Srivatsa's patch adds a call from hotplug_cfd() to > flush_smp_call_function_queue() to, which I imagine happens in > non-interrupt context. Note that this patch moves most of the body of > generic_smp_call_function_single_interrupt() into > flush_smp_call_function_queue(). -- 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/