linux-kernel - Re: workqueue deadlock

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Date:	Mon, 11 Dec 2006 12:22:28 +0530
From:	Dipankar Sarma <dipankar@...ibm.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu>,
	vatsa@...ibm.com, Bjorn Helgaas <bjorn.helgaas@...com>,
	linux-kernel@...r.kernel.org, Myron Stowe <myron.stowe@...com>,
	Jens Axboe <axboe@...nel.dk>, Gautham shenoy <ego@...ibm.com>,
	Pavel Machek <pavel@....cz>
Subject: Re: workqueue deadlock

On Sun, Dec 10, 2006 at 03:18:38PM +0100, Rafael J. Wysocki wrote:
> On Sunday, 10 December 2006 13:16, Andrew Morton wrote:
> > On Sun, 10 Dec 2006 12:49:43 +0100
> 
> Hm, currently we're using the CPU hotplug to disable the nonboot CPUs before
> the freezer is called. ;-)
> 
> However, we're now trying to make the freezer SMP-safe, so that we can disable
> the nonboot CPUs after devices have been suspended (we want to do this for
> some ACPI-related reasons).  In fact we're almost there, I'm only waiting for
> the confirmation from Pavel to post the patches.
> 
> When this is done, we won't need the CPU hotplug that much and I think the CPU
> hotplug code will be able to do something like:
> 
> freeze_processes
> suspend_cpufreq (or even suspend_all_devices)
> remove_the_CPU_in_question
> resume_cpufreq
> thaw_processes

Have you thought about how much time this might take on
a machine with say - 128 CPUs of which I want to dynamically
reconvigure 64 of them and make a new partition ? Assume
10,000 tasks are running in the system.

Thanks
Dipankar
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