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To: Matthew Garrett <mjg@redhat.com>
Cc: Tony Lindgren <tony@atomide.com>, Alan Stern <stern@rowland.harvard.edu>,
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Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 6)
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From: Kevin Hilman <khilman@deeprootsystems.com>
Organization: Deep Root Systems, LLC
Date: Fri, 14 May 2010 09:06:50 -0700
In-Reply-To: <20100513200814.GA20254@srcf.ucam.org> (Matthew Garrett's message of "Thu\, 13 May 2010 21\:08\:14 +0100")
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Matthew Garrett <mjg@redhat.com> writes:

> On Thu, May 13, 2010 at 01:00:04PM -0700, Tony Lindgren wrote:
>
>> The system stays running because there's something to do. The system
>> won't suspend until all the processors hit the kernel idle loop and
>> the next_timer_interrupt_critical() returns nothing.
>
> At which point an application in a busy loop cripples you. I think we 
> could implement your suggestion more easily by just giving untrusted 
> applications an effectively infinite amount of timer slack, 
>
> but it still doesn't handle the case where an app behaves
> excrutiatingly badly.

Is design for exruciatingly bad apps a design requirement?

If so, opportunistic suspend + suspend blockers fails as well.  An app
could easily hold a suspend blocker during its entire execution
crippling PM.

Using opportunistic suspend may possibly allow you contain bad
apps/drivers, but at the cost of having to patch already working and
trusted apps and known-working kernel code with suspend blockers.

IMO, rather than accepting a solution that allows bad apps to run
wild, it would be much better to _continue_ focus on tools for finding
and containing bad apps.  This approach has the added bonus of solving
problems on *every* linux-based system, not just Android.

Kevin