On Tue, Jan 20, 2015 at 03:20:00PM +0200, Alexander Shishkin wrote:
> > As for the exclusive events, how about something like the code below (on
> > top of the previous exclusive event patch)? The only remaining issue
> > that I see is creating cpu-wide events in the presence of per-thread
> > (event->cpu==-1) events. Both would still work, but only one of them
> > will actually get scheduled at a time. I'm thinking about adding a
> > counter for per-thread events to struct pmu for this purpose, so that if
> > any are present, we can disallow creating cpu-wide events. Or, we can
> > leave it as it is.
> >
> > What do you think?
> >
> > ---
> > kernel/events/core.c | 52
> > +++++++++++++++++++++++++++++++++++++++++++++++-----
> > 1 file changed, 47 insertions(+), 5 deletions(-)
> >
> > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > index cf0bf99f53..e8c86530e2 100644
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -7688,14 +7688,11 @@ static bool exclusive_event_match(struct perf_event
> > *e1, struct perf_event *e2)
> > return false;
> > }
> >
> > -static bool exclusive_event_ok(struct perf_event *event,
> > - struct perf_event_context *ctx)
> > +static bool __exclusive_event_ok(struct perf_event *event,
> > + struct perf_event_context *ctx)
> > {
> > struct perf_event *iter_event;
> >
> > - if (!(event->pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE))
> > - return true;
> > -
> > list_for_each_entry(iter_event, &ctx->event_list, event_entry) {
> > if (exclusive_event_match(iter_event, event))
> > return false;
> > @@ -7704,6 +7701,51 @@ static bool exclusive_event_ok(struct perf_event
> > *event,
> > return true;
> > }
> >
> > +static bool __exclusive_event_ok_on_cpu(struct perf_event *event, int cpu)
> > +{
> > + struct perf_event_context *cpuctx;
> > + bool ret;
> > +
> > + cpuctx = find_get_context(event->pmu, NULL, cpu);
> > + mutex_lock(&cpuctx->mutex);
> > + ret = __exclusive_event_ok(event, cpuctx);
> > + perf_unpin_context(cpuctx);
> > + put_ctx(cpuctx);
> > + mutex_unlock(&cpuctx->mutex);
>
> Actually, find_get_context() is not needed here, the following should be
> sufficient:
>
> cpuctx = &per_cpu_ptr(event->pmu->pmu_cpu_context, cpu)->ctx;
>
> mutex_lock(&cpuctx->mutex);
> ret = __exclusive_event_ok(event, cpuctx);
> mutex_unlock(&cpuctx->mutex);
Yes that'll work.
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