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Two fixes for performance monitoring on X86:

Browse Source 
- Add recursion protection to another callchain invoked from
       x86_pmu_stop() which can recurse back into x86_pmu_stop(). The first
       attempt to fix this missed this extra code path.
 
     - Use the already filtered status variable to check for PEBS counter
       overflow bits and not the unfiltered full status read from
       IA32_PERF_GLOBAL_STATUS which can have unrelated bits check which
       would be evaluated incorrectly.
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Merge tag 'perf-urgent-2020-12-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perf fixes from Thomas Gleixner:
 "Two fixes for performance monitoring on X86:

   - Add recursion protection to another callchain invoked from
     x86_pmu_stop() which can recurse back into x86_pmu_stop(). The
     first attempt to fix this missed this extra code path.

   - Use the already filtered status variable to check for PEBS counter
     overflow bits and not the unfiltered full status read from
     IA32_PERF_GLOBAL_STATUS which can have unrelated bits check which
     would be evaluated incorrectly"

* tag 'perf-urgent-2020-12-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/intel: Check PEBS status correctly
  perf/x86/intel: Fix a warning on x86_pmu_stop() with large PEBS
This commit is contained in:
Linus Torvalds 2020-12-06 11:20:18 -08:00
commit 9f6b28d498
1 changed files with 2 additions and 2 deletions
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4
arch/x86/events/intel/ds.c
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@ -1916,7 +1916,7 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs, struct perf_sample_d
* that caused the PEBS record. It's called collision.
* If collision happened, the record will be dropped.
*/
if (p->status != (1ULL << bit)) {
if (pebs_status != (1ULL << bit)) {
for_each_set_bit(i, (unsigned long *)&pebs_status, size)
error[i]++;
continue;
@ -1940,7 +1940,7 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs, struct perf_sample_d
if (error[bit]) {
perf_log_lost_samples(event, error[bit]);
if (perf_event_account_interrupt(event))
if (iregs && perf_event_account_interrupt(event))
x86_pmu_stop(event, 0);
}