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

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Date:	Wed, 11 Feb 2009 10:48:58 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Alok Kataria <akataria@...are.com>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [BUGFIX/x86] Fix initialization of wakeup_cpu.


* Ingo Molnar <mingo@...e.hu> wrote:

> 
> * Alok Kataria <akataria@...are.com> wrote:
> 
> > On Tue, 2009-02-10 at 16:31 -0800, Yinghai Lu wrote:
> > > > 
> > > >> 2. also will break 64 bit....
> > > > isn't the default_x86_quirks defined for 64 bit too ? 
> > > > 
> > > 64 bit doesn't have genapic_apic_probe()
> > > 
> > > need to change that to 
> > > #ifdef CONFIG_X86_32
> > > 	genapic_apic_probe();
> > > #endif
> > > 
> > 
> > Ok here it is. 
> > --
> > 
> > With 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 for 32 bit now.
> > 
> > Signed-off-by: Alok N Kataria <akataria@...are.com>
> > Cc: Yinghai Lu <yinghai@...nel.org>
> > 
> > Index: linux-tip-master/arch/x86/kernel/setup.c
> > ===================================================================
> > --- linux-tip-master.orig/arch/x86/kernel/setup.c	2009-02-10 12:05:18.000000000 -0800
> > +++ linux-tip-master/arch/x86/kernel/setup.c	2009-02-10 16:37:59.000000000 -0800
> > @@ -936,7 +936,7 @@
> >  	map_vsyscall();
> >  #endif
> >  
> > -#if defined(CONFIG_X86_32_NON_STANDARD) || defined(CONFIG_X86_BIGSMP)
> > +#ifdef CONFIG_X86_32
> >  	generic_apic_probe();
> >  #endif
> 
> Please extend 64-bit with generic_apic_probe() instead. (and please also
> make sure your patches build on a 64-bit defconfig)

I've applied your patch as an interim measure so far, to fix the crash,
so please do the cleaner patch ontop of your first patch. Thanks,

	Ingo
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