linux-kernel - Re: apm emulation driver broken ?

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Date:	Mon, 19 Nov 2007 14:05:04 +0100
From:	Franck Bui-Huu <vagabon.xyz@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	linux-pm@...ts.linux-foundation.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: apm emulation driver broken ?

Rafael J. Wysocki wrote:
> On Sunday, 18 of November 2007, Franck Bui-Huu wrote:
>> Rafael J. Wysocki wrote:
>> See the call to wait_even() made by apm_ioctl(). If any processes
>> run this, it will prevent the system to suspend...
> 
> True, but does it actually happen in practice?
> 

when several processes are waiting for a suspend event.

> 
> At this point the second branch of the "if (as->suspend_state == SUSPEND_READ)"
> can be fixed by replacing wait_event_interruptible() with
> wait_event_freezable(), 

yes

> but the fix for the first branch depends on whether or
> not the wait_event() is really necessary.

As I said I don't know. It's probably time to put some people
on CC but don't know who though.

> 
> If it can be replaced with an interruptible sleep, we can use
> wait_event_freezable() in this case too.  Otherwise, the only woking fix would
> be to reintroduce the PF_NOFREEZE in there.

BTW, why not raising PF_NOFREEZE in wait_event(), so thread sleeping
in UNINTERRUPTIBLE state won't prevent suspend to happen ?


		Franck
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