On 21/01/15 13:48, Daniel Thompson wrote: > On 21/01/15 13:06, Steven Rostedt wrote: >> On Wed, 21 Jan 2015 10:47:37 +0000 >> Daniel Thompson <daniel.thomp...@linaro.org> wrote: >> >> >>>> With this patchset, is it possible to call sched_clock() from within NMI >>>> context? I ask because the generic sched_clock() code is not NMI safe >> >> That's not good. Better not run function tracing, as that could trace >> functions in NMI context (I depend on that it does), and it uses >> sched_clock() as the default clock. > > I think sched_clock is unsafe as in "may sometimes give the wrong value" > rather than "can lock up arbitrarily". Thus the impact is unlikely to > be harmful enough to want to avoid tracing altogether.
Just to update the record... The above paragraph is wrong in every possible way. It is a livelock (and I'm working on it). > It would require special care be taken when interpreting the timestamps > however. Also since update_sched_clock() is a notrace function its very > hard to figure out when timestamps are at risk. > > Anyhow, the fix doesn't seem that hard. I can take a look. > > > Daniel. > -- 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/
