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Date: Fri, 27 Mar 2015 17:35:47 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        John Stultz <john.stultz@linaro.org>, "H. Peter Anvin" <hpa@zytor.com>,
        David Ahern <dsahern@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>
Subject: Re: [tip:perf/timer] perf: Add per event clockid support
Message-ID: <20150327163547.GI23123@twins.programming.kicks-ass.net>
References: <tip-34f439278cef7b1177f8ce24f9fc81dfc6221d3b@git.kernel.org>
 <CABPqkBTKYRU1uwhfWXhWKeqYmWCukXLrinvwtfC9xN4Fy=+2yg@mail.gmail.com>
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On Fri, Mar 27, 2015 at 09:31:45AM -0700, Stephane Eranian wrote:
> On Fri, Mar 27, 2015 at 4:48 AM, tip-bot for Peter Zijlstra
> > +static int perf_event_set_clock(struct perf_event *event, clockid_t clk_id)
> > +{
> > +       bool nmi_safe = false;
> > +
> > +       switch (clk_id) {
> > +       case CLOCK_MONOTONIC:
> > +               event->clock = &ktime_get_mono_fast_ns;
> > +               nmi_safe = true;
> > +               break;
> > +
> > +       case CLOCK_MONOTONIC_RAW:
> > +               event->clock = &ktime_get_raw_fast_ns;
> > +               nmi_safe = true;
> > +               break;
> > +
> > +       case CLOCK_REALTIME:
> > +               event->clock = &ktime_get_real_ns;
> > +               break;
> > +
> > +       case CLOCK_BOOTTIME:
> > +               event->clock = &ktime_get_boot_ns;
> > +               break;
> > +
> > +       case CLOCK_TAI:
> > +               event->clock = &ktime_get_tai_ns;
> > +               break;
> > +
> Can all those clocks be safely called from an NMI context?

+       if (!nmi_safe && !(event->pmu->capabilities & PERF_PMU_CAP_NO_NMI))
+               return -EINVAL;

no :-)