linux-kernel - Re: [PATCH 1/3] PM / Sleep: Make [un]lock_system

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Date:	Mon, 05 Dec 2011 22:55:51 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Tejun Heo <tj@...nel.org>
CC:	rjw@...k.pl, pavel@....cz, len.brown@...el.com,
	ebiederm@...ssion.com, rdunlap@...otime.net,
	linux-doc@...r.kernel.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 1/3] PM / Sleep: Make [un]lock_system_sleep() generic

On 12/05/2011 10:44 PM, Tejun Heo wrote:

> Hello,
> 
> On Mon, Dec 05, 2011 at 01:32:38AM +0530, Srivatsa S. Bhat wrote:
>> +static inline void lock_system_sleep(void)
>> +{
>> +	/* simplified freezer_do_not_count() */
>> +	current->flags |= PF_FREEZER_SKIP;
>> +	mutex_lock(&pm_mutex);
>> +}
>> +
>> +static inline void unlock_system_sleep(void)
>> +{
>> +	mutex_unlock(&pm_mutex);
>> +	/* simplified freezer_count() */
>> +	current->flags &= ~PF_FREEZER_SKIP;
>> +}
> 
> BTW, don't we want try_to_freeze() there?  What's the reason for not
> using freezer_count()?
> 

I wanted these APIs to be generic, not restricted to work only for userspace
processes. Both freezer_do_not_count() and freezer_count() are effective only
when current->mm is non-NULL (ie., only for userspace ones).
I think I have documented this in the patch which added these things to the
2 APIs. See commit 6a76b7a in linux-pm/linux-next.

As for try_to_freeze(), we can surely add that. I think I missed it while
open-coding the relevant part of freezer_count(). I'll send it as a separate
patch. Thank you very much.

Regards,
Srivatsa S. Bhat

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