Re: [BUGFIX][PATCH] Freezer, CPU hotplug, x86 Microcode: Fix taskfreezing failures

From: Borislav Petkov
Date: Tue Oct 04 2011 - 09:26:04 EST

On Tue, Oct 04, 2011 at 12:15:08AM -0700, Tejun Heo wrote:
> On Mon, Oct 03, 2011 at 10:47:54AM +0200, Borislav Petkov wrote:
> > I think your patch makes sense because re-loading the ucode during
> > a suspend/resume cycle is unnecessary. If one wants to update the
> > microcode, it should happen later when the box is resumed again: you
> > simply put the new microcode image in /lib/firmware/... and on AMD
> > unload/reload the microcode module and on Intel you do either that or
> > use the deprecated microcode_ctl.
> I don't think it changes anything for suspend/resume cycles. They're
> different hooks. The proposed patch changes actual cpu hotplug paths.

Well, we're offlining the CPUs through the same hotplug path when
suspending and since currently the microcode core unnecessarily
re-requests the ucode image from userspace on resume, I still think the
patch makes sense. Especially if Srivatsa does suspend/resume and CPU
hotplugging simultaneously in a test and upon onlining a CPU, he manages
of doing request_firmware on a frozen userspace.

Srivatsa, is my understanding correct?


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