Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759294AbbKST7N (ORCPT ); Thu, 19 Nov 2015 14:59:13 -0500 Received: from casper.infradead.org ([85.118.1.10]:45109 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759226AbbKST7K (ORCPT ); Thu, 19 Nov 2015 14:59:10 -0500 Date: Thu, 19 Nov 2015 20:59:05 +0100 From: Peter Zijlstra To: Jacob Pan Cc: Thomas Gleixner , Ingo Molnar , John Stultz , LKML , Arjan van de Ven , Srinivas Pandruvada , Len Brown , Rafael Wysocki , Eduardo Valentin , Paul Turner , Josh Triplett , "Paul E. McKenney" Subject: Re: [PATCH 2/4] timer: relax tick stop in idle entry Message-ID: <20151119195905.GR3816@twins.programming.kicks-ass.net> References: <1447444387-23525-1-git-send-email-jacob.jun.pan@linux.intel.com> <1447444387-23525-3-git-send-email-jacob.jun.pan@linux.intel.com> <20151113142438.3144d47d@icelake> <20151116135126.5a50e45d@icelake> <20151116160910.3811c8ca@icelake> <20151119190630.GP3816@twins.programming.kicks-ass.net> <20151119112125.743f12d7@icelake> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151119112125.743f12d7@icelake> 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 Content-Length: 1374 Lines: 37 On Thu, Nov 19, 2015 at 11:21:25AM -0800, Jacob Pan wrote: > On Thu, 19 Nov 2015 20:06:30 +0100 > Peter Zijlstra wrote: > > > Which one? That is, I cannot find a idle_cpu() call from > > tick_nohz_irq_exit(). > it is tick_irq_exit(void), i will not call tick_nohz_irq_exit() if > !idle_cpu() Ah, but I think we really only need to test for the idle task there, the && need_resched() part of that function takes care of the rest. Once we have need_resched() set, we'll be on our way to tick_nohz_idle_exit() to restart the tick again. --- kernel/softirq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/softirq.c b/kernel/softirq.c index 479e4436f787..3bd30404f2ee 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -367,7 +367,7 @@ static inline void tick_irq_exit(void) int cpu = smp_processor_id(); /* Make sure that timer wheel updates are propagated */ - if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { + if ((is_idle_task(current) && !need_resched()) || tick_nohz_full_cpu(cpu)) { if (!in_interrupt()) tick_nohz_irq_exit(); } -- 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/