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

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Date:	Mon, 06 Nov 2006 15:15:38 +0100
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	linux-kernel@...r.kernel.org
Cc:	shaohua.li@...el.com, akpm@...l.org, bunk@...sta.de
Subject: [patch] Regression in 2.6.19-rc microcode driver

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.

Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>

--- linux-2.6.18/arch/i386/kernel/microcode.c.org	2006-11-06 14:50:37.000000000 +0100
+++ linux-2.6.18/arch/i386/kernel/microcode.c	2006-11-06 14:52:30.000000000 +0100
@@ -577,7 +577,7 @@ static void microcode_init_cpu(int cpu)
 	set_cpus_allowed(current, cpumask_of_cpu(cpu));
 	mutex_lock(&microcode_mutex);
 	collect_cpu_info(cpu);
-	if (uci->valid)
+	if (uci->valid && system_state==SYSTEM_RUNNING)
 		cpu_request_microcode(cpu);
 	mutex_unlock(&microcode_mutex);
 	set_cpus_allowed(current, old);

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