Messages in this thread | | | Date | Thu, 6 May 2010 18:48:54 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [PATCH -tip] x86,perf: P4 PMU -- protect sensible procedures from preemption |
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On Thu, May 06, 2010 at 09:45:24AM -0400, Steven Rostedt wrote: ... > > > We want the one with the least runtime overhead. These are instrumentation > > > routines, so we want to optimize them as much as possible. > > > Yeah, my point was either disable preemption or keep the checks. In > other words, if you don't disable preemption, do not use > raw_smp_procesor_id(), because then we will not catch it if it changes > in the future. > > > ok, Ingo, dont apply this patch then for a while. > > Send another patch, I'll test it again ;-) > > -- Steve > >
Ingo, Steven, it seems we have potential preemtion available in perf_event.c:validate_group:x86_pmu.schedule_events() which is reached via syscall from userspace perf_event_open() call, so get_cpu is still needed. But I'm a bit messed with call graph at the moment :(
-- Cyrill
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