Re: [RFC PATCH(Experimental) 2/4] Revert changes to workqueue.c

From: Oleg Nesterov
Date: Tue Feb 20 2007 - 15:10:42 EST

On 02/20, Srivatsa Vaddagiri wrote:
> On Sun, Feb 18, 2007 at 12:59:28AM +0300, Oleg Nesterov wrote:
> > Before you begin. You are doing CPU_DOWN_PREPARE after freeze_processes().
> > Not good. This makes impossible to do flush_workueue() at CPU_DOWN_PREPARE
> > stage, we have callers.
> We have few solutions to deal with this:
> a. Mark such workqueues not freezable for hotplug
> b. If above is not possible, don't call flush_workqueue in DOWN_PREPARE
> c. If above is not possible, send DOWN_PREPARE before freeze_processes()
> I would prefer a solution in the above order listed.
> Which caller are you referring to here? Maybe we can decide on the
> option after we see the users of flush_workqueue() in DOWN_PREPARE.


> > I'm afraid it won't be so easy to solve all locking/racing problems. Will
> > wait for the patch :)
> I dont see problems for workqueue.c even if we follow option c. Do you
> see any?

I don't right now... Oh, I already forgot everything :) I'll try to recall
when I see the patch.


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