On Tue, Aug 04, 2015 at 08:58:15AM +0000, Kaixu Xia wrote:
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 6251b53..726ca1b 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -8599,6 +8599,25 @@ struct perf_event_attr *perf_event_attrs(struct
> perf_event *event)
> return &event->attr;
> }
>
> +u64 perf_event_read_internal(struct perf_event *event)
Maybe: perf_event_read_local(), as this is this function only works for
events active on the current CPU.
> +{
> + if (!event)
> + return -EINVAL;
> +
> + if (unlikely(event->state != PERF_EVENT_STATE_ACTIVE))
> + return -EINVAL;
You can return perf_event_count() in that case.
> +
> + if (event->oncpu != raw_smp_processor_id() &&
That _must_ be smp_processor_id(). If that gives a warning (ie.
preemption is not disabled or we're not affine to this one cpu) then the
warning is valid.
> + event->ctx->task != current)
Write it like:
if (event->ctx->task != current &&
event->oncpu != smp_processor_id())
That way you'll not evaluate smp_processor_id() for current task events.
> + return -EINVAL;
> +
> + if (unlikely(event->attr.inherit))
> + return -EINVAL;
This should be in your accept function, inherited events should never
get this far.
You need IRQs disabled while calling __perf_event_read(), did you test
with lockdep enabled?
> + __perf_event_read(event);
> + return perf_event_count(event);
> +}
Also, you probably want a WARN_ON(in_nmi()) there, this function is
_NOT_ NMI safe.
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