Messages in this thread | | | Date | Mon, 29 Sep 2014 17:28:32 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/2] perf: Add sampling of the raw monotonic clock |
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On Thu, Sep 18, 2014 at 03:34:32PM +0100, Pawel Moll wrote: > @@ -4456,6 +4459,13 @@ static void __perf_event_header__init_id(struct perf_event_header *header, > data->cpu_entry.cpu = raw_smp_processor_id(); > data->cpu_entry.reserved = 0; > } > + > + if (sample_type & PERF_SAMPLE_CLOCK_RAW_MONOTONIC) { > + struct timespec now; > + > + getrawmonotonic(&now); > + data->clock_raw_monotonic = timespec_to_ns(&now); > + } > } >
This cannot work, getrawmonotonic() isn't NMI-safe and there's nothing stopping this being used from NMI context.
Also getrawmonotonic() + timespec_to_ns() will make tglx sad, he's just done a tree-wide eradication of silly conversions and now you're adding a ns -> timespec -> ns dance right back.
I _think_ you want ktime_get_mono_fast_ns(), but this does bring us right back to the question/discussion on which timebase you'd want to sync again. MONO does make sense for most cases, but I think we've had fairly sane stories for people wanting to sync against other clocks.
A well..
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