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authorAlexander Shishkin <alexander.shishkin@linux.intel.com>2019-12-10 12:51:01 +0200
committerPeter Zijlstra <peterz@infradead.org>2019-12-17 13:32:46 +0100
commit92ca7da4bdc24d63bb0bcd241c11441ddb63b80a (patch)
tree149940e4c77a558df00df7038a6aa6f6eb48942f /arch/x86/events
parentff61541cc6c1962957758ba433c574b76f588d23 (diff)
downloadlinux-92ca7da4bdc24d63bb0bcd241c11441ddb63b80a.tar.gz
perf/x86/intel: Fix PT PMI handling
Commit: ccbebba4c6bf ("perf/x86/intel/pt: Bypass PT vs. LBR exclusivity if the core supports it") skips the PT/LBR exclusivity check on CPUs where PT and LBRs coexist, but also inadvertently skips the active_events bump for PT in that case, which is a bug. If there aren't any hardware events at the same time as PT, the PMI handler will ignore PT PMIs, as active_events reads zero in that case, resulting in the "Uhhuh" spurious NMI warning and PT data loss. Fix this by always increasing active_events for PT events. Fixes: ccbebba4c6bf ("perf/x86/intel/pt: Bypass PT vs. LBR exclusivity if the core supports it") Reported-by: Vitaly Slobodskoy <vitaly.slobodskoy@intel.com> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Alexey Budankov <alexey.budankov@linux.intel.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Link: https://lkml.kernel.org/r/20191210105101.77210-1-alexander.shishkin@linux.intel.com
Diffstat (limited to 'arch/x86/events')
-rw-r--r--arch/x86/events/core.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 84fe1becbe26..f118af9f0718 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -376,7 +376,7 @@ int x86_add_exclusive(unsigned int what)
* LBR and BTS are still mutually exclusive.
*/
if (x86_pmu.lbr_pt_coexist && what == x86_lbr_exclusive_pt)
- return 0;
+ goto out;
if (!atomic_inc_not_zero(&x86_pmu.lbr_exclusive[what])) {
mutex_lock(&pmc_reserve_mutex);
@@ -388,6 +388,7 @@ int x86_add_exclusive(unsigned int what)
mutex_unlock(&pmc_reserve_mutex);
}
+out:
atomic_inc(&active_events);
return 0;
@@ -398,11 +399,15 @@ fail_unlock:
void x86_del_exclusive(unsigned int what)
{
+ atomic_dec(&active_events);
+
+ /*
+ * See the comment in x86_add_exclusive().
+ */
if (x86_pmu.lbr_pt_coexist && what == x86_lbr_exclusive_pt)
return;
atomic_dec(&x86_pmu.lbr_exclusive[what]);
- atomic_dec(&active_events);
}
int x86_setup_perfctr(struct perf_event *event)