Re: [PATCH 2/2] perf_counter: optimize context switch betweenidentical inherited contexts

[Peter Zijlstra]

On Fri, 2009-05-22 at 14:27 +1000, Paul Mackerras wrote:
> +       next_ctx = next->perf_counter_ctxp;
> +       if (next_ctx && context_equiv(ctx, next_ctx)) {
> +               task->perf_counter_ctxp = next_ctx;
> +               next->perf_counter_ctxp = ctx;
> +               ctx->task = next;
> +               next_ctx->task = task;
> +               return;
> +       }

Ingo just pointed out that there is nothing there to close the race with
attaching a counter.

That is, you could end up attaching your counter to the wrong task.

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