linux-kernel - Re: [RFC 2/2] clocksource: don't suspend/resume when unused

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <54B8EA54.5020002@linaro.org>
Date:	Fri, 16 Jan 2015 11:39:16 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Thomas Gleixner <tglx@...utronix.de>
CC:	John Stultz <john.stultz@...aro.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 2/2] clocksource: don't suspend/resume when unused

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 <alexandre.belloni@...e-electrons.com>
>>> ---
>>>   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.


-- 
  <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/