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Message-ID: <7c86c4470811270547y370e0be6keef6aadffa16581f@mail.gmail.com>
Date: Thu, 27 Nov 2008 14:47:20 +0100
From: "stephane eranian" <eranian@googlemail.com>
Reply-To: eranian@gmail.com
To: "Andi Kleen" <andi@firstfloor.org>
Subject: Re: [patch 05/24] perfmon: X86 generic code (x86)
Cc: "Thomas Gleixner" <tglx@linutronix.de>, linux-kernel@vger.kernel.org,
       akpm@linux-foundation.org, mingo@elte.hu, x86@kernel.org,
       sfr@canb.auug.org.au
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On Thu, Nov 27, 2008 at 2:49 PM, Andi Kleen <andi@firstfloor.org> wrote:
>> What about a thread doing this and another one in the middle of read the buffer?
>
> I assume that uses locks. Locking between threads is easy.
>
I think that is fine as long as the interrupt handler does not need to
grab locks.
But that, in turn, means that the state needed/modified by the handler cannot
be altered in any other way that could be harmful.

>>
>> Or what about a thread trying to reset the buffer while you're processing an PMU
>> interrupt on another CPU. I know each buffer is per-CPU, but that does not
>> prevent two threads for trying to operate on it at the same time from
>> different CPUs.
>
> That happens per CPU.
>
So you're saying a thread can only access the buffer from the CPU it
is running on?
--
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