linux-kernel - Re: [RFC] [patch 4/6 -rt] powerpc 2.6.20-rt8: fix a runtime warnings for xmon

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Date:	Wed, 7 Mar 2007 10:16:38 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Tsutomu OWA <tsutomu.owa@...hiba.co.jp>
Cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] [patch 4/6 -rt] powerpc 2.6.20-rt8: fix a runtime warnings for xmon

* Tsutomu OWA <tsutomu.owa@...hiba.co.jp> wrote:

> @@ -342,6 +342,7 @@ static int xmon_core(struct pt_regs *reg
>  
>  	msr = mfmsr();
>  	mtmsr(msr & ~MSR_EE);	/* disable interrupts */
> +	preempt_disable();

i'm not an xmon expert, but maybe it might make more sense to first 
disable preemption, then interrupts - otherwise you could be preempted 
right after having disabled these interrupts (and be scheduled to 
another CPU, etc.). What is the difference between local_irq_save() and 
the above 'disable interrupts' sequence? If it's not the same and 
xmon_core() relied on having hardirqs disabled then it might make sense 
to do a local_irq_save() there, instead of a preempt_disable().

	Ingo
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