linux-kernel - Re: BUG: null pointer deref in dmar_ir

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Date:	Fri, 02 Apr 2010 11:28:33 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"Jan.Grossmann@...lnet.net" <Jan.Grossmann@...lnet.net>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"jbarnes@...tuousgeek.org" <jbarnes@...tuousgeek.org>,
	"Woodhouse, David" <david.woodhouse@...el.com>,
	"Han, Weidong" <weidong.han@...el.com>,
	"Song, Youquan" <youquan.song@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"stable@...nel.org" <stable@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: BUG: null pointer deref in dmar_ir_support

On Fri, 2010-04-02 at 11:20 -0700, Ingo Molnar wrote:
> * Suresh Siddha <suresh.b.siddha@...el.com> wrote:
> 
> > @@ -1640,8 +1640,10 @@ int __init APIC_init_uniprocessor(void)
> >  	}
> >  #endif
> >  
> > +#ifndef CONFIG_SMP
> >  	enable_IR_x2apic();
> >  	default_setup_apic_routing();
> > +#endif
> 
> Instead of adding yet another ugly #ifdef please hide these details properly, 
> by making enable_IR_x2apic() and default_setup_apic_routing() a NOP on !SMP.

Ingo, These are not nops on !SMP. We should call these functions from
APIC_init_uniprocessor() only if it is a UP kernel. For SMP kernel they
are called from some where else.

With the current code, on SMP and with non SMP motherboard we were
calling these routines twice which cause problem.

I wanted to keep the patch simple for urgent/backport. I will clean this
by restructuring the init code for 2.6.35

thanks,
suresh

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