On Thu, Jan 22, 2015 at 1:39 PM, Stephane Eranian <[email protected]> wrote: > On Thu, Jan 22, 2015 at 2:17 AM, Peter Zijlstra <[email protected]> wrote: >> On Wed, Jan 21, 2015 at 09:13:11PM -0800, Stephane Eranian wrote: >>> Vince, >>> >>> On Wed, Jan 21, 2015 at 10:55 AM, Vince Weaver <[email protected]> >>> wrote: >>> > Hello >>> > >>> > on my haswell system, running 3.19-rc5, and with >>> > echo "0" > /proc/sys/kernel/perf_event_paranoid >>> > >>> > I can easily crash my system with the attached test program that simply >>> > opens a RAPL event and then closes it. >>> > >>> > This bug was found by the perf_fuzzer. >>> > >>> > It looks like somehow rapl_pmu gets freed to NULL but the >>> > call in rapl_scale() >>> > __this_cpu_read(rapl_pmu->hw_unit) >>> > still happens. >>> > >>> I don't see how this can happen. >>> >>> I get some crashes but not with your program on my laptop. >>> But I cannot catch the serial console from my laptop. >>> Will try with another machine tomorrow. >> >> I saw it today as well on an ivb-ep. I disabled rapl for now since I'm >> chasing other things. > > I will fix that today.
Ok, problem identified. One liner. Bug introduced by: commit 89cbc76768c2fa4ed95545bf961f3a14ddfeed21 Author: Christoph Lameter <[email protected]> Date: Sun Aug 17 12:30:40 2014 -0500 x86: Replace __get_cpu_var uses Fix looks like this: diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c index 6e434f8..c4bb8b8 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c +++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c @@ -142,7 +142,7 @@ static inline u64 rapl_scale(u64 v) * or use ldexp(count, -32). * Watts = Joules/Time delta */ - return v << (32 - __this_cpu_read(rapl_pmu->hw_unit)); + return v << (32 - __this_cpu_read(rapl_pmu)->hw_unit); } Will post the patch shortly. Thanks Vince for reporting this issue. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
