perf pmu: Don't double count common sysfs and json events

After pmu_add_cpu_aliases() is called, perf_pmu__num_events() returns an
incorrect value that double counts common events and doesn't match the
actual count of events in the alias list. This is because after
'cpu_aliases_added == true', the number of events returned is
'sysfs_aliases + cpu_json_aliases'. But when adding 'case
EVENT_SRC_SYSFS' events, 'sysfs_aliases' and 'cpu_json_aliases' are both
incremented together, failing to account that these ones overlap and
only add a single item to the list. Fix it by adding another counter for
overlapping events which doesn't influence 'cpu_json_aliases'.

There doesn't seem to be a current issue because it's used in perf list
before pmu_add_cpu_aliases() so the correct value is returned. Other
uses in tests may also miss it for other reasons like only looking at
uncore events. However it's marked as a fixes commit in case any new fix
with new uses of perf_pmu__num_events() is backported.

Fixes: d9c5f5f ("perf pmu: Count sys and cpuid JSON events separately")
Reviewed-by: Ian Rogers <[email protected]>
Signed-off-by: James Clark <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Namhyung Kim <[email protected]>

Author: james-c-linaro

tools/perf/util/pmu.c

@@ -595,7 +595,7 @@ static int perf_pmu__new_alias(struct perf_pmu *pmu, const char *name,
 			};
 			if (pmu_events_table__find_event(pmu->events_table, pmu, name,
 							 update_alias, &data) == 0)
-				pmu->cpu_json_aliases++;
+				pmu->cpu_common_json_aliases++;
 		}
 		pmu->sysfs_aliases++;
 		break;
@@ -1880,9 +1880,10 @@ size_t perf_pmu__num_events(struct perf_pmu *pmu)
 	if (pmu->cpu_aliases_added)
 		 nr += pmu->cpu_json_aliases;
 	else if (pmu->events_table)
-		nr += pmu_events_table__num_events(pmu->events_table, pmu) - pmu->cpu_json_aliases;
+		nr += pmu_events_table__num_events(pmu->events_table, pmu) -
+			pmu->cpu_common_json_aliases;
 	else
-		assert(pmu->cpu_json_aliases == 0);
+		assert(pmu->cpu_json_aliases == 0 && pmu->cpu_common_json_aliases == 0);
 
 	if (perf_pmu__is_tool(pmu))
 		nr -= tool_pmu__num_skip_events();

tools/perf/util/pmu.h

@@ -136,6 +136,11 @@ struct perf_pmu {
 	uint32_t cpu_json_aliases;
 	/** @sys_json_aliases: Number of json event aliases loaded matching the PMU's identifier. */
 	uint32_t sys_json_aliases;
+	/**
+	 * @cpu_common_json_aliases: Number of json events that overlapped with sysfs when
+	 * loading all sysfs events.
+	 */
+	uint32_t cpu_common_json_aliases;
 	/** @sysfs_aliases_loaded: Are sysfs aliases loaded from disk? */
 	bool sysfs_aliases_loaded;
 	/**