linux-kernel - [055/139] x86: Fix double enable_IR_x2apic() call on SMP kernel on !SMP boards

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Message-Id: <20100422195410.361876407@kvm.kroah.org>
Date:	Thu, 22 Apr 2010 12:53:52 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	<jbarnes@...tuousgeek.org>, <david.woodhouse@...el.com>,
	<weidong.han@...el.com>, <youquan.song@...el.com>,
	<Jan.Grossmann@...lnet.net>, Ingo Molnar <mingo@...e.hu>
Subject: [055/139] x86: Fix double enable_IR_x2apic() call on SMP kernel on !SMP boards

2.6.33-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Suresh Siddha <suresh.b.siddha@...el.com>

commit 472a474c6630efd195d3738339fd1bdc8aa3b1aa upstream.

Jan Grossmann reported kernel boot panic while booting SMP
kernel on his system with a single core cpu. SMP kernels call
enable_IR_x2apic() from native_smp_prepare_cpus() and on
platforms where the kernel doesn't find SMP configuration we
ended up again calling enable_IR_x2apic() from the
APIC_init_uniprocessor() call in the smp_sanity_check(). Thus
leading to kernel panic.

Don't call enable_IR_x2apic() and default_setup_apic_routing()
from APIC_init_uniprocessor() in CONFIG_SMP case.

NOTE: this kind of non-idempotent and assymetric initialization
sequence is rather fragile and unclean, we'll clean that up
in v2.6.35. This is the minimal fix for v2.6.34.

Reported-by: Jan.Grossmann@...lnet.net
Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
Cc: <jbarnes@...tuousgeek.org>
Cc: <david.woodhouse@...el.com>
Cc: <weidong.han@...el.com>
Cc: <youquan.song@...el.com>
Cc: <Jan.Grossmann@...lnet.net>
LKML-Reference: <1270083887.7835.78.camel@...-t61.sc.intel.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/x86/kernel/apic/apic.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1640,8 +1640,10 @@ int __init APIC_init_uniprocessor(void)
 	}
 #endif
 
+#ifndef CONFIG_SMP
 	enable_IR_x2apic();
 	default_setup_apic_routing();
+#endif
 
 	verify_local_APIC();
 	connect_bsp_APIC();


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