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| author |   Doug Smythies <doug.smythies@gmail.com> | 2017-08-08 14:12:49 -0700 |
|---|---|---|
| committer |   Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2017-08-11 01:27:41 +0200 |
| commit | 8e2f3bce05e056575c2c84a344a8291fdabb5f21 (patch) | |
| tree | 0a68d4997d6c9d4e9b77faceca9132ab1d9120d8 /arch | |
| parent | Linux 4.13-rc4 (diff) | |
| download | linux-dev-8e2f3bce05e056575c2c84a344a8291fdabb5f21.tar.xz linux-dev-8e2f3bce05e056575c2c84a344a8291fdabb5f21.zip | |
cpufreq: x86: Disable interrupts during MSRs reading
According to Intel 64 and IA-32 Architectures SDM, Volume 3,
Chapter 14.2, "Software needs to exercise care to avoid delays
between the two RDMSRs (for example interrupts)".
So, disable interrupts during reading MSRs IA32_APERF and IA32_MPERF.
See also: commit 4ab60c3f32c7 (cpufreq: intel_pstate: Disable
interrupts during MSRs reading).
Signed-off-by: Doug Smythies <dsmythies@telus.net>
Reviewed-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/cpu/aperfmperf.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c index 7cf7c70b6ef2..0ee83321a313 100644 --- a/arch/x86/kernel/cpu/aperfmperf.c +++ b/arch/x86/kernel/cpu/aperfmperf.c @@ -40,13 +40,16 @@ static void aperfmperf_snapshot_khz(void *dummy) struct aperfmperf_sample *s = this_cpu_ptr(&samples); ktime_t now = ktime_get(); s64 time_delta = ktime_ms_delta(now, s->time); + unsigned long flags; /* Don't bother re-computing within the cache threshold time. */ if (time_delta < APERFMPERF_CACHE_THRESHOLD_MS) return; + local_irq_save(flags); rdmsrl(MSR_IA32_APERF, aperf); rdmsrl(MSR_IA32_MPERF, mperf); + local_irq_restore(flags); aperf_delta = aperf - s->aperf; mperf_delta = mperf - s->mperf; |