linux-kernel - Re: [PATCH 7/9] PM: Add suspend blocking work.

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Message-ID: <i2ld6200be21004232221h2c03ec1alb3d1152142e35fda@mail.gmail.com>
Date:	Fri, 23 Apr 2010 22:21:34 -0700
From:	Arve Hjønnevåg <arve@...roid.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Tejun Heo <tj@...nel.org>, linux-pm@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitri Vorobiev <dmitri.vorobiev@...ial.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 7/9] PM: Add suspend blocking work.

2010/4/23 Arve Hjønnevåg <arve@...roid.com>:
> On Fri, Apr 23, 2010 at 5:20 AM, Oleg Nesterov <oleg@...hat.com> wrote:
>> On 04/23, Tejun Heo wrote:
>>>
>>> On 04/23/2010 03:08 AM, Arve Hjønnevåg wrote:
>>> > Allow work to be queued that will block suspend while it is pending
>>> > or executing. To get the same functionality in the calling code often
>>> > requires a separate suspend_blocker for pending and executing work, or
>>> > additional state and locking.
>>>
>>> Hmm... I think this can be implemented as pure wrapper around
>>> workqueue instead of injecting a flag and code into workqueue core.
>>> Adding @fn field to suspend_blocking_work struct and using a custom
>>> work function to call it and then invoke suspend_unblock() should be
>>> enough, right?  Oh, dedicated queue functions will be needed too.  I
>>> don't think it's wise to meddle with workqueue core code for this.
>>
>> Completely agreed. The patch adds very "strange" hacks into workqueue
>> code to solve the very specific problems.
>>
>
> I want the suspend blocker active when the work is pending or running.
> I did not see a way to do this on top of the workqueue api without
> adding additional locking.
>

I can remove the WORK_STRUCT_SUSPEND_BLOCKING flag and instead add an
argument to __queue_work and __cancel_work_timer (or use separate
copies) if you think that would be better. It would avoid increasing
the alignment requirement of cpu_workqueue_struct, but it will
probably add more code than the current patch.

-- 
Arve Hjønnevåg
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