Subject: Re: [patch] Regression in 2.6.19-rc microcode driver
From: Shaohua Li <shaohua.li@intel.com>
To: Arjan van de Ven <arjan@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, akpm@osdl.org, bunk@stusta.de
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Date: Tue, 07 Nov 2006 09:20:27 +0800
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On Mon, 2006-11-06 at 15:15 +0100, Arjan van de Ven wrote:
> Hi,
> 
> if the microcode driver is built in (rather than module) there are some,
> ehm, interesting effects happening due to the new "call out to
> userspace" behavior that is introduced.. and which runs too early. The
> result is a boot hang; which is really nasty.
> 
> The patch below is a minimally safe patch to fix this regression for
> 2.6.19 by just not requesting actual microcode updates during early
> boot. (That is a good idea in general anyway)
> 
> The "real" fix is a lot more complex given the entire cpu hotplug
> scenario (during cpu hotplug you normally need to load the microcode as
> well); but the interactions for that are just really messy at this
> point; this fix at least makes it work and avoids a full detangle of
> hotplug.
Yes, this is an issue which I documented in my patch. It's not a hang,
but a long delay if you have many cpus. Other drivers with firmware
request have the same issue if they are built-in. Maybe we should fix
the firmware request mechanism itself. I hope no distribution has
microcode driver built-in.

Thanks,
Shaohua
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