On Wed, Jan 6, 2016 at 1:46 PM, tip-bot for Peter Zijlstra
<tipbot@xxxxxxxxx> wrote:
>
> This is because context switches can swap the task_struct::perf_event_ctxp[]
> pointer around. Therefore you have to either disable preemption when looking
> at current, or hold ctx->lock.
>
>
> void perf_event_exec(void)
> {
> - struct perf_event_context *ctx;
> int ctxn;
>
> rcu_read_lock();
Do we still need this rcu_read_lock(), if perf_event_enable_on_exec()
uses local_irq_save( ?
> - for_each_task_context_nr(ctxn) {
> - ctx = current->perf_event_ctxp[ctxn];
> - if (!ctx)
> - continue;
> -
> - perf_event_enable_on_exec(ctx);
> - }
> + for_each_task_context_nr(ctxn)
> + perf_event_enable_on_exec(ctxn);
> rcu_read_unlock();
> }
>
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