diff options
| author | Kan Liang | 2015-08-17 08:37:31 -0400 |
|---|---|---|
| committer | Ingo Molnar | 2015-09-13 11:27:22 +0200 |
| commit | deb27519bf1f4b21a761c0675dbdf1196df7d72a (patch) | |
| tree | 3c7f88c756c4316b8e10265147b9c84795124797 /arch | |
| parent | d2878d642a4edd1d57c691dc3e4d7847cbf9d442 (diff) | |
perf/x86/intel: Fix LBR callstack issue caused by FREEZE_LBRS_ON_PMI
This patch fixes an issue which introduced by commit
1a78d93750bb5f61abdc59a91fc3bd06a214542a ("perf/x86/intel: Streamline
LBR MSR handling in PMI").
The old patch not only avoids writing LBR_SELECT MSR in PMI, but also
avoids updating lbr_select variable. So in PMI, FREEZE_LBRS_ON_PMI bit
is always mistakenly set for IA32_DEBUGCTLMSR MSR, which causes
superfluous increase/decrease of LBR_TOS when collecting LBR callstack.
Reported-by: Milian Wolff <mail@milianw.de>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1439815051-8616-1-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/cpu/perf_event_intel_lbr.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c index b2c9475b7ff2..a1d07c71d3b6 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c @@ -151,10 +151,9 @@ static void __intel_pmu_lbr_enable(bool pmi) * No need to reprogram LBR_SELECT in a PMI, as it * did not change. */ - if (cpuc->lbr_sel && !pmi) { - lbr_select = cpuc->lbr_sel->config; + lbr_select = cpuc->lbr_sel->config; + if (cpuc->lbr_sel && !pmi) wrmsrl(MSR_LBR_SELECT, lbr_select); - } rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl); orig_debugctl = debugctl; |