From: Ingo Molnar Date: Fri, 15 May 2009 06:25:22 +0000 (+0200) Subject: perf_counter: x86: Disallow interval of 1 X-Git-Tag: firefly_0821_release~13973^2~274 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=1c80f4b598d9b075a2a0be694e28be93a6702bcc;p=firefly-linux-kernel-4.4.55.git perf_counter: x86: Disallow interval of 1 On certain CPUs i have observed a stuck PMU if interval was set to 1 and NMIs were used. The PMU had PMC0 set in MSR_CORE_PERF_GLOBAL_STATUS, but it was not possible to ack it via MSR_CORE_PERF_GLOBAL_OVF_CTRL, and the NMI loop got stuck infinitely. [ Impact: fix rare hangs during high perfcounter load ] Signed-off-by: Peter Zijlstra Cc: Paul Mackerras Cc: Corey Ashford LKML-Reference: Signed-off-by: Ingo Molnar --- diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index 1dcf67057f16..46a82d1e4cbe 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -473,6 +473,11 @@ x86_perf_counter_set_period(struct perf_counter *counter, left += period; atomic64_set(&hwc->period_left, left); } + /* + * Quirk: certain CPUs dont like it if just 1 event is left: + */ + if (unlikely(left < 2)) + left = 2; per_cpu(prev_left[idx], smp_processor_id()) = left;