Messages in this thread | | | From | Alexander Shishkin <> | Subject | Re: [PATCH 1/2] perf/x86/intel/pt: Fail event scheduling on conflict with VMX | Date | Tue, 14 Feb 2017 19:21:34 +0200 |
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Peter Zijlstra <peterz@infradead.org> writes:
> On Tue, Feb 14, 2017 at 06:17:30PM +0200, Alexander Shishkin wrote: >> This is called by pmu::add(), which checks hw.state afterwards and if it >> finds HES_STOPPED, it returns an error, which event_sched_in() captures >> and keeps the event in INACTIVE state. Should I add a comment about it? > > Egads... so what if ->add() succeeds but we then hit this on > ->stop()/->start() due to throttle or period adjust?
It will hang there with hw.state==PERF_HES_STOPPED till the next sched_out. But that will be the case anyway if VMXON kicks in while PT is running.
> Now I suppose PT will never normally hit either of those, but you can do > IOC_PERIOD on it, just for giggles.
True. Should we worry?
> Yes, this very much needs a comment... Also, should not this then live > in ->add() in the first place?
The output_stop() stuff in the mmap_close path relies on perf_aux_output_end() being in ->stop(), let me think if there's more.
Regards, -- Alex
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