From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752971AbbBYOiy (ORCPT ); Wed, 25 Feb 2015 09:38:54 -0500 Received: from foss.arm.com ([217.140.101.70]:37738 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752357AbbBYOiw (ORCPT ); Wed, 25 Feb 2015 09:38:52 -0500 Date: Wed, 25 Feb 2015 14:39:17 +0000 From: Lorenzo Pieralisi To: Daniel Lezcano Cc: "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Rafael J. Wysocki" Subject: Re: [PATCH 1/2] drivers: cpuidle: remove stale irq disabling call in cpuidle_enter_freeze() Message-ID: <20150225143917.GC20214@red-moon> References: <1424800730-32059-1-git-send-email-lorenzo.pieralisi@arm.com> <1424800730-32059-2-git-send-email-lorenzo.pieralisi@arm.com> <54EDD883.30608@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54EDD883.30608@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 25, 2015 at 02:13:23PM +0000, Daniel Lezcano wrote: > On 02/24/2015 06:58 PM, Lorenzo Pieralisi wrote: > > On return from cpuidle_enter_freeze() irqs are re-enabled by the function > > caller (ie cpuidle_idle_call) in the idle loop. This patch removes a stale > > local_irq_disable() call and its stale comment in cpuidle_enter_freeze(), > > since they disagree and do not serve a useful purpose. > > > > Cc: Rafael J. Wysocki > > Cc: Daniel Lezcano > > Signed-off-by: Lorenzo Pieralisi > > --- > > drivers/cpuidle/cpuidle.c | 3 --- > > 1 file changed, 3 deletions(-) > > > > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > > index 4d53458..f47edc6c 100644 > > --- a/drivers/cpuidle/cpuidle.c > > +++ b/drivers/cpuidle/cpuidle.c > > @@ -144,9 +144,6 @@ void cpuidle_enter_freeze(void) > > cpuidle_enter(drv, dev, index); > > else > > arch_cpu_idle(); > > - > > - /* Interrupts are enabled again here. */ > > - local_irq_disable(); > > } > > Hmm, I think Rafael added this prevent lockdep to raise a warning. Ok, so the comment is there to say "at this point of execution IRQs are enabled", it does not refer to local_irq_disable() call effects, that's misleading and not necessarily nice, at least it should be explained. > Otherwise, cpuidle_enter or arch_cpu_idle enables the irq again and then > when exiting the cpu_idle_call, we enable them again, so leading to a > lockdep WARN in trace_hardirqs_on_caller. Would not it be better to enable irqs in cpuidle_enter_freeze() on returning from enter_freeze_proper() and remove the local_irq_enable() call in the cpuidle_idle_call() before jumping to exit_idle ? > That said, if we have to do this, it may reveal something is wrong in > the code. I just spotted code through inspection, I have to say at the moment it is not very clear what it is meant to achieve, so I put together this patch. Lorenzo