From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 13 Oct 2008 17:15:23 +0000 (+0000)
Subject: x86: improve UP kernel when CPU-hotplug and SMP is enabled
X-Git-Tag: v2.6.25.19~14
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=75402d996fe1fe834ce1d1ed5d600407b23a8713;p=thirdparty%2Fkernel%2Fstable.git

x86: improve UP kernel when CPU-hotplug and SMP is enabled

commit 649c6653fa94ec8f3ea32b19c97b790ec4e8e4ac upstream

num_possible_cpus() can be > 1 when disabled CPUs have been accounted.

Disabled CPUs are not in the cpu_present_map, so we can use
num_present_cpus() as a safe indicator to switch to UP alternatives.

Reported-by: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 5fed98ca0e1f0..2fb2dfeeee22e 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -457,7 +457,7 @@ void __init alternative_instructions(void)
 					    _text, _etext);
 
 		/* Only switch to UP mode if we don't immediately boot others */
-		if (num_possible_cpus() == 1 || setup_max_cpus <= 1)
+		if (num_present_cpus() == 1 || setup_max_cpus <= 1)
 			alternatives_smp_switch(0);
 	}
 #endif