linux-kernel - Re: [patch] Regression in 2.6.19-rc microcode driver

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Message-Id: <1162862427.22565.4.camel@sli10-conroe.sh.intel.com>
Date:	Tue, 07 Nov 2006 09:20:27 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...l.org, bunk@...sta.de
Subject: Re: [patch] Regression in 2.6.19-rc microcode driver

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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