linux-kernel - [BUGFIX/x86] Fix initialization of wakeup

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Date:	Tue, 10 Feb 2009 12:28:35 -0800
From:	Alok Kataria <akataria@...are.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [BUGFIX/x86] Fix initialization of wakeup_cpu.

Was originally reported in the..
"Re: [PARAVIRT/x86] BUGFIX: Put a missing paravirt_release_pmd in pgd_dtor" thread

--
With the patches for refactoring of wake_cpu macros, the 32bit code
in tip doesn't execute generic_apic_probe if CONFIG_X86_32_NON_STANDARD
is not set.

Even on a x86 STANDARD cpu we need to execute the generic_apic_probe
function, as we rely on this function to execute the update_genapic
quirk which initilizes apic->wakeup_cpu. 

Failing to do so results in we making a call to a null function in do_boot_cpu.

The stack trace without the patch goes like this.

Booting processor 1 APIC 0x1 ip 0x6000
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<(null)>] (null)
*pdpt = 0000000000839001 *pde = 0000000000c97067 *pte = 0000000000000163 
Oops: 0000 [#1] SMP 
last sysfs file: 
Modules linked in:

Pid: 1, comm: swapper Not tainted (2.6.29-rc4-tip #18) VMware Virtual Platform
EIP: 0062:[<00000000>] EFLAGS: 00010293 CPU: 0
EIP is at 0x0
EAX: 00000001 EBX: 00006000 ECX: c077ed00 EDX: 00006000
ESI: 00000001 EDI: 00000001 EBP: ef04cf40 ESP: ef04cf1c
 DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 006a
Process swapper (pid: 1, ti=ef04c000 task=ef050000 task.ti=ef04c000)
Stack:
 c0644e52 00000000 ef04cf24 ef04cf24 c064468d c0886dc0 00000000 c0702aea
 ef055480 00000001 00000101 dead4ead ffffffff ffffffff c08af530 00000000
 c0709715 ef04cf60 ef04cf60 00000001 00000000 00000000 dead4ead ffffffff
Call Trace:
 [<c0644e52>] ? native_cpu_up+0x2de/0x45b
 [<c064468d>] ? do_fork_idle+0x0/0x19
 [<c0645c5e>] ? _cpu_up+0x88/0xe8
 [<c0645d20>] ? cpu_up+0x42/0x4e
 [<c07e7462>] ? kernel_init+0x99/0x14b
 [<c07e73c9>] ? kernel_init+0x0/0x14b
 [<c040375f>] ? kernel_thread_helper+0x7/0x10
Code:  Bad EIP value.
EIP: [<00000000>] 0x0 SS:ESP 006a:ef04cf1c

I think we should call generic_apic_probe unconditionally now.

Signed-off-by: Alok N Kataria <akataria@...are.com>

Index: linux-tip-master/arch/x86/kernel/setup.c
===================================================================
--- linux-tip-master.orig/arch/x86/kernel/setup.c	2009-02-10 11:37:31.000000000 -0800
+++ linux-tip-master/arch/x86/kernel/setup.c	2009-02-10 11:50:37.000000000 -0800
@@ -936,9 +936,7 @@
 	map_vsyscall();
 #endif
 
-#if defined(CONFIG_X86_32_NON_STANDARD) || defined(CONFIG_X86_BIGSMP)
 	generic_apic_probe();
-#endif
 
 	early_quirks();
 


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