On Mon, Jun 19, 2017 at 08:01:07PM +0530, Naveen N. Rao wrote:
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 6c4e523dc1e2..812fcfc767f4 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -2679,7 +2679,8 @@ static int _perf_event_refresh(struct perf_event
> *event, int refresh)
> /*
> * not supported on inherited events
That comment wants updating to explain the signal crud..
> */
> - if (event->attr.inherit || !is_sampling_event(event))
> + if (event->attr.inherit || event->attr.signal_on_wakeup ||
> + !is_sampling_event(event))
> return -EINVAL;
>
> atomic_add(refresh, &event->event_limit);
> @@ -7362,12 +7362,15 @@ static int __perf_event_overflow(struct perf_event
> *event,
> * events
> */
>
> + if (!event->attr.signal_on_wakeup) {
> + int events = atomic_read(&event->event_limit);
> + event->pending_kill = POLL_IN;
> + if (events && atomic_dec_and_test(&event->event_limit)) {
> + ret = 1;
> + event->pending_kill = POLL_HUP;
>
> + perf_event_disable_inatomic(event);
> + }
> }
So even without event_limit (IOC_REFRESH) this would've generated
SIGIO:POLL_IN.
>
> READ_ONCE(event->overflow_handler)(event, data, regs);
> @@ -10408,6 +10411,7 @@ perf_event_exit_event(struct perf_event *child_event,
> perf_group_detach(child_event);
> list_del_event(child_event, child_ctx);
> child_event->state = PERF_EVENT_STATE_EXIT; /* is_event_hup() */
> + child_event->pending_kill = POLL_HUP;
This looks like an undocumented change..
> raw_spin_unlock_irq(&child_ctx->lock);
>
> /*
> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
> index 2831480c63a2..4e7c728569a8 100644
> --- a/kernel/events/ring_buffer.c
> +++ b/kernel/events/ring_buffer.c
> @@ -21,6 +21,9 @@ static void perf_output_wakeup(struct perf_output_handle
> *handle)
> {
> atomic_set(&handle->rb->poll, POLLIN);
>
> + if (handle->event->attr.signal_on_wakeup)
> + handle->event->pending_kill = POLL_IN;
> +
And this is the bit that generates SIGIO:POLL_IN on wakeup.
> handle->event->pending_wakeup = 1;
> irq_work_queue(&handle->event->pending);
> }
> --
> 2.13.1
>
