linux-kernel - Re: [PATCH v2 03/10] freezer: add new freezable helpers using freezer_do_not

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Date:	Thu, 2 May 2013 19:16:59 -0700
From:	Colin Cross <ccross@...roid.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Arve Hjønnevåg <arve@...roid.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Jeff Layton <jlayton@...hat.com>
Subject: Re: [PATCH v2 03/10] freezer: add new freezable helpers using freezer_do_not_count()

This sounds the same as what ended up getting reverted in
https://lkml.org/lkml/2013/3/4/221
I can add the WARN_ON_ONCE to all my new calls, and leave them out of
existing calls, but that seems a little odd, and will be redundant if
the lockdep call in try_to_freeze goes back in in 3.11.  Do you still
want it in the new apis?

On Thu, May 2, 2013 at 5:03 PM, Tejun Heo <tj@...nel.org> wrote:
> On Thu, May 02, 2013 at 04:55:05PM -0700, Tejun Heo wrote:
>> So, the freezable interface can't be something that people can use
>> casually.  It is something which should be carefully and strategically
>> deployed where we *know* that lock dependency risks don't exist or at
>> least are acceptable.  I'm a bit weary that this patch is expanding
>> the interface a lot that they now look like the equivalents of normal
>> schedule calls.  Not exactly sure what to do here but can we please at
>> least have RED BOLD BLINKING comments which scream to people not to
>> use these unless they know what they're doing?
>
> Maybe we should trigger WARN_ON_ONCE() if lockdep_depth() > 0 by
> default and have ugly variants which can be used if the caller is sure
> that it's okay possibly with list of locks which are held?
>
> --
> tejun
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