Messages in this thread | | | Date | Thu, 2 Apr 2009 20:21:35 +1100 | From | Paul Mackerras <> | Subject | Re: [PATCH 2/9] perf_counter: fix update_userpage() |
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Peter Zijlstra writes:
> The below might work: > > u32 seq; > s64 count; > > again: > seq = pc->lock; > > if (unlikely(seq & 1)) {
I don't believe we can ever see this condition, since pc->lock is updated in the kernel either at interrupt level on the cpu this task is running on, or in the kernel in the context of this task. So this userspace code can never run in the middle of the kernel updating things.
Paul.
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