Patch "perf/cgroup: Fix perf cgroup hierarchy support" has been added to the 4.13-stable tree

This is a note to let you know that I've just added the patch titled

perf/cgroup: Fix perf cgroup hierarchy support

to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
perf-cgroup-fix-perf-cgroup-hierarchy-support.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Tejun Heo <[email protected]>
Date: Sat, 28 Oct 2017 09:49:37 -0700
Subject: perf/cgroup: Fix perf cgroup hierarchy support

From: Tejun Heo <[email protected]>

commit be96b316deff35e119760982c43af74e606fa143 upstream.

The following commit:

864c2357ca89 ("perf/core: Do not set cpuctx->cgrp for unscheduled cgroups")

made list_update_cgroup_event() skip setting cpuctx->cgrp if no cgroup event targets %current's cgroup.

This breaks perf_event's hierarchical support because events which target one of the ancestors get ignored.

Fix it by using cgroup_is_descendant() test instead of equality.

---
 kernel/events/core.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

@@ -901,9 +901,11 @@ list_update_cgroup_event(struct perf_eve
 	cpuctx_entry = &cpuctx->cgrp_cpuctx_entry;
 	/* cpuctx->cgrp is NULL unless a cgroup event is active in this CPU .*/
 	if (add) {
+		struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx);
+
 		list_add(cpuctx_entry, this_cpu_ptr(&cgrp_cpuctx_list));
-		if (perf_cgroup_from_task(current, ctx) == event->cgrp)
-			cpuctx->cgrp = event->cgrp;
+		if (cgroup_is_descendant(cgrp->css.cgroup, event->cgrp->css.cgroup))
+			cpuctx->cgrp = cgrp;
 	} else {
 		list_del(cpuctx_entry);
 		cpuctx->cgrp = NULL;

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/perf-cgroup-fix-perf-cgroup-hierarchy-support.patch