> >>+static void pmu_disable_counters_ctrl(struct cci_pmu *cci_pmu, unsigned
> >>long *mask)
> >>+{
> >>+ int i;
> >>+
> >>+ for (i = 0; i < cci_pmu->num_cntrs; i++) {
> >>+ clear_bit(i, mask);
> >>+ if (pmu_get_counter_ctrl(cci_pmu, i)) {
> >>+ set_bit(i, mask);
> >>+ pmu_disable_counter(cci_pmu, i);
> >>+ }
> >>+ }
> >>+}
> >
> >I don't understand what's going on with the mask here. Why do we clear
> >ieach bit when the only user (introduced in the next patch) explicitly
> >clears the mask anyway?
>
> To be more precise, it should have been :
>
> if (pmu_get_counter_ctrl(cci_pmu, i)) {
> set_bit(i, mask);
> pmu_disable_counter(cci_pmu, i);
> } else
> clear_bit(i, mask);
>
> >
> >Can we not get rid of the mask entirely? The combination of used_mask
> >and each event's hwc->state tells us which counters are actually in use.
>
> The problem is that neither hwc->state nor the cci_pmu->hw_events->events is
> protected by pmu_lock, while enable/disable counter is. So we cannot really
> rely on ((struct perf_event
> *)(cci_pmu->hw_events->events[counter]))->hw->state.
They must be protected somehow, or we'd have races against cross-calls
and/or the interrupt handler.
Are we protected due to being cpu-affine with interrupts disabled when
modifying these, is there some other mechanism that protects us, or do
we have additional problems here?
Thanks,
Mark.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
