linux-kernel - Re: [PATCH 02/10] freezer: skip waking up tasks with PF_FREEZER

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Message-ID: <20130429215745.GB2395@htj.dyndns.org>
Date:	Mon, 29 Apr 2013 14:57:45 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Colin Cross <ccross@...roid.com>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>, arve@...roid.com,
	Li Zefan <lizefan@...wei.com>, Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org
Subject: Re: [PATCH 02/10] freezer: skip waking up tasks with PF_FREEZER_SKIP
 set

On Mon, Apr 29, 2013 at 02:51:57PM -0700, Tejun Heo wrote:
> I feel a bit weary of changes which try to optimize state checks for
> freezer because the synchronization rules are kinda fragile and things
> may not work reliably depending on who's testing the flag, and it has
> been subtly broken in various ways in the past (maybe even now).  Can

And BTW, this is why the function is only used when checking whether a
task is frozen rather than to decide to issue freeze_task() on it, and
it seems your change is correct now that we don't have per-task FREEZE
flag but I can't say I like the change.  I'd really like to keep
things as dumb as possible for freezer.

Thanks.

-- 
tejun
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