linux-kernel - Re: [PATCH 0/8] Suspend block api (version 7)

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Date:	Mon, 17 May 2010 16:32:48 -0700
From:	Arve Hjønnevåg <arve@...roid.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Brian Swetland <swetland@...gle.com>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/8] Suspend block api (version 7)

On Mon, May 17, 2010 at 2:44 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> On Monday 17 May 2010, Brian Swetland wrote:
>> On Mon, May 17, 2010 at 1:40 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
>> > On Monday 17 May 2010, Arve Hjønnevåg wrote:
>> >>
>> >> It should get out of that loop as soon as someone blocks suspend. If
>> >> someone is constantly aborting suspend without using a suspend blocker
>> >> it will be very inefficient, but it should still work.
>> >
>> > Well, the scenario I have in mind is the following.  Someone wants to check
>> > the feature and simply writes "opportunistic" to /sys/power/policy and "mem" to
>> > /sys/power/state without any drivers or apps that use suspend blockers.
>> >
>> > How in that case is the system supposed to break out of the suspend-resume loop
>> > resulting from this?  I don't see right now, because the main blocker is
>> > inactive, there are no other blockers that can be activated and it is next to
>> > impossible to write to /sys/power/state again.
>>
>> I guess we could set a flag when a suspend blocker is registered and
>> refuse to enter opportunistic mode if no blockers have ever been
>> registered.
>>
>> It does seem like extra effort to go through to handle a "don't do
>> that" type scenario (entering into opportunistic suspend without
>> anything that will prevent it).
>
> I agree, but I think it's necessary.  We shouldn't add interfaces that hurt
> users if not used with care.
>

I'm not sure this can be "fixed". The user asked that the system to
suspend whenever possible, which is what it is doing. I don't think
disabling opportunistic suspend if no suspend blockers have been
registered will work. As soon as we register a suspend blocker we are
back in the same situation.

-- 
Arve Hjønnevåg
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