linux-kernel - Re: apm emulation driver broken ?

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Message-ID: <473ED715.9000004@gmail.com>
Date:	Sat, 17 Nov 2007 12:57:09 +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 Saturday, 17 of November 2007, Franck Bui-Huu wrote:
>> Rafael J. Wysocki wrote:
>>> However, using PF_NOFREEZE to prevent this from happening doesn't seem to be
>>> a good idea.
>>>
>> Indeed but...
>>
>>> I'd probably use wait_event_freezable() (defined in
>>> include/linux/freezer.h) for that.
>> ...I would just revert this bits from now to make sure this driver
>> work again for v2.6.24.
> 
> I'd prefer not to.
> 
> The PF_NOFREEZE was not present in 2.6.23 already and I wouldn't like to
> reintroduce it now.
> 
> Why do you think that using wait_event_freezable() would not work, BTW?
> 

I've never claimed this. I just said it may be safer to revert the
changes for v2.6.24 and improve the current code for next releases.

>>> It tries to send them fake signals and waits for them to freeze.  If
>>> they don't freeze within the timeout, it fails and clears their
>>> TIF_FREEZE bits.
>> But send_fake_signal() seems to wake up task in INTERRUPTIBLE state
>> only. Looking at signal_wake_up(), it basically do:
>>
>> 	wake_up_state(t, TASK_INTERRUPTIBLE);
>>
>> What am I missing ?
> 
> Nothing. :-)
> 
> I didn't remember the change that made the freezer use TASK_INTERRUPTIBLE
> explicitly in there (should have looked at the current code before replying).
> 

ok so now we agreed on this point, can we assert that a user
land thread waiting for an event in an UNINTERRUPTIBLE state
will prevent a suspend to happen ?

		Franck
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