From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755995AbaFYKTZ (ORCPT ); Wed, 25 Jun 2014 06:19:25 -0400 Received: from casper.infradead.org ([85.118.1.10]:57608 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755904AbaFYKTW (ORCPT ); Wed, 25 Jun 2014 06:19:22 -0400 Date: Wed, 25 Jun 2014 12:19:15 +0200 From: Peter Zijlstra To: "Srivatsa S. Bhat" Cc: Stephen Warren , Frederic Weisbecker , LKML , Andrew Morton , Eric Dumazet , Ingo Molnar , Kevin Hilman , "Paul E. McKenney" , Thomas Gleixner , Viresh Kumar , "linux-next@vger.kernel.org" Subject: Re: [PATCH 2/6] irq_work: Implement remote queueing Message-ID: <20140625101915.GO19860@laptop.programming.kicks-ass.net> References: <1402413309-3415-1-git-send-email-fweisbec@gmail.com> <1402413309-3415-3-git-send-email-fweisbec@gmail.com> <53A9E0A5.5040402@wwwdotorg.org> <20140625051234.GD6758@twins.programming.kicks-ass.net> <20140625051721.GG3588@twins.programming.kicks-ass.net> <53AA6E11.1000404@linux.vnet.ibm.com> <20140625093657.GN19860@laptop.programming.kicks-ass.net> <20140625093944.GV16155@laptop.programming.kicks-ass.net> <53AA9B68.4050104@linux.vnet.ibm.com> <53AA9C43.3020903@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53AA9C43.3020903@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 25, 2014 at 03:24:11PM +0530, Srivatsa S. Bhat wrote: > Wait, that was a stupid idea. hotplug_cfd() already invokes irq_work_run > indirectly via flush_smp_call_function_queue(). So irq_work_cpu_notify() > doesn't need to invoke it again, AFAIU. So perhaps we can get rid of > irq_work_cpu_notify() altogether? Just so... getting up at 6am and sitting in an airport terminal doesn't seem to agree with me; any more silly fail here? --- Subject: irq_work: Remove BUG_ON in irq_work_run() From: Peter Zijlstra Date: Wed Jun 25 07:13:07 CEST 2014 Because of a collision with 8d056c48e486 ("CPU hotplug, smp: flush any pending IPI callbacks before CPU offline"), which ends up calling hotplug_cfd()->flush_smp_call_function_queue()->irq_work_run(), which is not from IRQ context. And since that already calls irq_work_run() from the hotplug path, remove our entire hotplug handling. Cc: Frederic Weisbecker Reported-by: Stephen Warren Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-busatzs2gvz4v62258agipuf@git.kernel.org --- kernel/irq_work.c | 48 +++++------------------------------------------- 1 file changed, 5 insertions(+), 43 deletions(-) Index: linux-2.6/kernel/irq_work.c =================================================================== --- linux-2.6.orig/kernel/irq_work.c +++ linux-2.6/kernel/irq_work.c @@ -160,20 +160,14 @@ static void irq_work_run_list(struct lli } } -static void __irq_work_run(void) -{ - irq_work_run_list(&__get_cpu_var(raised_list)); - irq_work_run_list(&__get_cpu_var(lazy_list)); -} - /* - * Run the irq_work entries on this cpu. Requires to be ran from hardirq - * context with local IRQs disabled. + * hotplug calls this through: + * hotplug_cfs() -> flush_smp_call_function_queue() */ -void irq_work_run(void) +static void irq_work_run(void) { - BUG_ON(!in_irq()); - __irq_work_run(); + irq_work_run_list(&__get_cpu_var(raised_list)); + irq_work_run_list(&__get_cpu_var(lazy_list)); } EXPORT_SYMBOL_GPL(irq_work_run); @@ -189,35 +183,3 @@ void irq_work_sync(struct irq_work *work cpu_relax(); } EXPORT_SYMBOL_GPL(irq_work_sync); - -#ifdef CONFIG_HOTPLUG_CPU -static int irq_work_cpu_notify(struct notifier_block *self, - unsigned long action, void *hcpu) -{ - long cpu = (long)hcpu; - - switch (action) { - case CPU_DYING: - /* Called from stop_machine */ - if (WARN_ON_ONCE(cpu != smp_processor_id())) - break; - __irq_work_run(); - break; - default: - break; - } - return NOTIFY_OK; -} - -static struct notifier_block cpu_notify; - -static __init int irq_work_init_cpu_notifier(void) -{ - cpu_notify.notifier_call = irq_work_cpu_notify; - cpu_notify.priority = 0; - register_cpu_notifier(&cpu_notify); - return 0; -} -device_initcall(irq_work_init_cpu_notifier); - -#endif /* CONFIG_HOTPLUG_CPU */