From mboxrd@z Thu Jan 1 00:00:00 1970 From: daniel.lezcano@linaro.org (Daniel Lezcano) Date: Fri, 16 Jan 2015 11:39:16 +0100 Subject: [RFC 2/2] clocksource: don't suspend/resume when unused In-Reply-To: <20150116103530.GB3843@piout.net> 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> Message-ID: <54B8EA54.5020002@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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