From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754194AbbAPKjX (ORCPT ); Fri, 16 Jan 2015 05:39:23 -0500 Received: from mail-wi0-f170.google.com ([209.85.212.170]:48381 "EHLO mail-wi0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751980AbbAPKjU (ORCPT ); Fri, 16 Jan 2015 05:39:20 -0500 Message-ID: <54B8EA54.5020002@linaro.org> Date: Fri, 16 Jan 2015 11:39:16 +0100 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Alexandre Belloni , Thomas Gleixner CC: John Stultz , Nicolas Ferre , Boris Brezillon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC 2/2] clocksource: don't suspend/resume when unused References: <1421399874-29119-1-git-send-email-alexandre.belloni@free-electrons.com> <1421399874-29119-3-git-send-email-alexandre.belloni@free-electrons.com> <20150116103530.GB3843@piout.net> In-Reply-To: <20150116103530.GB3843@piout.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/16/2015 11:35 AM, Alexandre Belloni wrote: > On 16/01/2015 at 11:23:32 +0100, Thomas Gleixner wrote : >> On Fri, 16 Jan 2015, Alexandre Belloni wrote: >> >>> There is no point in calling suspend/resume for unused >>> clocksources. >>> >>> Signed-off-by: Alexandre Belloni >>> --- >>> kernel/time/clocksource.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c >>> index 920a4da58eb0..baea4e42ae90 100644 >>> --- a/kernel/time/clocksource.c >>> +++ b/kernel/time/clocksource.c >>> @@ -493,7 +493,7 @@ void clocksource_suspend(void) >>> struct clocksource *cs; >>> >>> list_for_each_entry_reverse(cs, &clocksource_list, list) >>> - if (cs->suspend) >>> + if (cs->suspend && (cs->flags & CLOCK_SOURCE_USED)) >>> cs->suspend(cs); >> >> This might be dangerous. If the clocksource has no enable/disable >> callbacks, but suspend/resume, then you might leave it enabled across >> suspend. >> > > Isn't that already the case? > Right now, if you call clocksource_suspend, it doesn't matter whether > the clocksource has an enable or not, it will be suspended. Maybe I'm > mistaken but my patch doesn't seem to change that behaviour. Actually, if there is no enable/disable callback, then CLOCK_SOURCE_USED will be never set, hence the condition will always fail and the suspend callback won't be called. -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog