Re: [patch 05/24] perfmon: X86 generic code (x86)

["stephane eranian" <eranian@googlemail.com>]

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?