From: Kan Liang kan.liang@linux.intel.com
A warning in intel_pmu_lbr_counters_reorder() may be triggered by below perf command.
perf record -e "{cpu-clock,cycles/call-graph="lbr"/}" -- sleep 1
It's because the group is mistakenly treated as a branch counter group.
The hw.flags of the leader are used to determine whether a group is a branch counters group. However, the hw.flags is only available for a hardware event. The field to store the flags is a union type. For a software event, it's a hrtimer. The corresponding bit may be set if the leader is a software event.
For a branch counter group and other groups that have a group flag (e.g., topdown, PEBS counters snapshotting, and ACR), the leader must be a X86 event. Check the X86 event before checking the flag. The patch only fixes the issue for the branch counter group. The following patch will fix the other groups.
There may be an alternative way to fix the issue by moving the hw.flags out of the union type. It should work for now. But it's still possible that the flags will be used by other types of events later. As long as that type of event is used as a leader, a similar issue will be triggered. So the alternative way is dropped.
Fixes: 33744916196b ("perf/x86/intel: Support branch counters logging") Reported-by: Luo Gengkun luogengkun@huaweicloud.com Closes: https://lore.kernel.org/lkml/20250412091423.1839809-1-luogengkun@huaweicloud... Signed-off-by: Kan Liang kan.liang@linux.intel.com Cc: stable@vger.kernel.org --- arch/x86/events/perf_event.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h index 902bc42a6cfe..4fc61a09c30e 100644 --- a/arch/x86/events/perf_event.h +++ b/arch/x86/events/perf_event.h @@ -110,9 +110,16 @@ static inline bool is_topdown_event(struct perf_event *event) return is_metric_event(event) || is_slots_event(event); }
+int is_x86_event(struct perf_event *event); + +static inline bool check_leader_group(struct perf_event *leader, int flags) +{ + return is_x86_event(leader) ? !!(leader->hw.flags & flags) : false; +} + static inline bool is_branch_counters_group(struct perf_event *event) { - return event->group_leader->hw.flags & PERF_X86_EVENT_BRANCH_COUNTERS; + return check_leader_group(event->group_leader, PERF_X86_EVENT_PEBS_CNTR); }
static inline bool is_pebs_counter_event_group(struct perf_event *event) @@ -1129,7 +1136,6 @@ static struct perf_pmu_format_hybrid_attr format_attr_hybrid_##_name = {\ .pmu_type = _pmu, \ }
-int is_x86_event(struct perf_event *event); struct pmu *x86_get_pmu(unsigned int cpu); extern struct x86_pmu x86_pmu __read_mostly;