Date: Thu, 9 Apr 2009 07:20:02 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] perf_counter: powerpc: add nmi_enter/nmi_exit calls
Message-ID: <20090409052002.GE5352@elte.hu>
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* Paul Mackerras <paulus@samba.org> wrote:

> Impact: powerpc bug fix
> 
> Now that the core is using in_nmi() (added in e30e08f6, 
> "perf_counter: fix NMI race in task clock"), we need the powerpc 
> perf_counter_interrupt to call nmi_enter() and nmi_exit() in those 
> cases where the interrupt happens when interrupts are 
> soft-disabled.  If interrupts were soft-enabled, we can treat it 
> as a regular interrupt and do irq_enter/irq_exit around the whole 
> routine.  This lets us get rid of the test_perf_counter_pending() 
> call at the end of perf_counter_interrupt, thus simplifying things 
> a little.

applied, thanks Paul!

I'm wondering, what was the real impact? Was it a crash or some 
other misbehavior? This impact line:

	Impact: powerpc bug fix

is a bit too generic to be useful in practice. Something like:

	Impact: fix stuck NMIs on powerpc
	Impact: fix NMI crash on powerpc

would have been more descriptive about the real, hands-on impact of 
this patch.

	Ingo
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