[PATCH v2 4/6] perf/core: Use stable cpuctx->cgrp when update perf cgroup time

[Chengming Zhou]

The current code use the changeable task->cgroups when update
the perf cgroup time, which maybe not the active perf_cgroup
that sched_in on the CPU.

This patch change to use the stable cpuctx->cgrp and only
update time when event is matched with cpuctx->cgrp.

Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
---
 kernel/events/core.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index e27c06628bad..849a81299906 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -780,7 +780,6 @@ static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx,
 static inline void update_cgrp_time_from_event(struct perf_event *event)
 {
 	struct perf_cgroup_info *info;
-	struct perf_cgroup *cgrp;
 
 	/*
 	 * ensure we access cgroup data only when needed and
@@ -789,11 +788,10 @@ static inline void update_cgrp_time_from_event(struct perf_event *event)
 	if (!is_cgroup_event(event))
 		return;
 
-	cgrp = perf_cgroup_from_task(current, event->ctx);
 	/*
-	 * Do not update time when cgroup is not active
+	 * Only update time when event is matched with cpuctx cgrp
 	 */
-	if (cgroup_is_descendant(cgrp->css.cgroup, event->cgrp->css.cgroup)) {
+	if (perf_cgroup_match(event)) {
 		info = this_cpu_ptr(event->cgrp->info);
 		__update_cgrp_time(info, perf_clock(), true);
 	}
-- 
2.20.1