On Fri, Apr 22, 2016 at 07:19:11PM +0300, Alexander Shishkin wrote:
> +static int perf_event_restart(struct perf_event *event)
> +{
> + struct stop_event_data sd = {
> + .event = event,
> + .restart = 1,
> + };
> + int ret = 0;
> +
> + do {
> + if (READ_ONCE(event->state) != PERF_EVENT_STATE_ACTIVE)
> + return 0;
> +
> + /* matches smp_wmb() in event_sched_in() */
> + smp_rmb();
> +
> + ret = cpu_function_call(READ_ONCE(event->oncpu),
> + __perf_event_stop, &sd);
> + } while (ret == -EAGAIN);
> +
> + return ret;
> +}
A few concerns with this;
- if I understand things right; this will loose a bit of trace when
people tickle the ioctl(), right? This might want a note of sorts,
- you need to handle event->oncpu == -1,
- can we race with an actual stop, and accidentally re-enable the
thing? If not, this might be a good place for a comment explaining
how.
