Re: [PATCH 09/12] perf_events: add hook to flush branch_stack oncontext switch (v2)

[Peter Zijlstra]

On Fri, 2011-10-14 at 14:37 +0200, Stephane Eranian wrote:
> +               /*
> +                * check if the context has at least one
> +                * event using PERF_SAMPLE_BRANCH_STACK
> +                */
> +               if (cpuctx->ctx.nr_branch_stack > 0
> +                   && pmu->flush_branch_stack) {
> +
> +                       pmu = cpuctx->ctx.pmu;
> +
> +                       perf_ctx_lock(cpuctx, cpuctx->task_ctx);
> +
> +                       perf_pmu_disable(pmu);
> +
> +                       pmu->flush_branch_stack();
> +
> +                       perf_pmu_enable(pmu);
> +
> +                       perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
> +               }
> +       } 

(what whitespace looks funny)

So all PMUs not supporting this branch stuff will fail to create a
has_branch_stack() event, right? Thus all ctx with !0 nr_branch_stack
support it. Doesn't this make the test for pmu->flush_branch_stack
redundant?


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