[PATCH v8 -tip 22/26] sched/debug: Add CGroup node for printing group cookie if SCHED_DEBUG

[Joel Fernandes (Google)]

This will be used by kselftest to verify the CGroup cookie value that is
set by the CGroup interface.

Tested-by: Julien Desfossez <jdesfossez@xxxxxxxxxxxxxxxx>
Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
---
 kernel/sched/core.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1321c26a8385..b3afbba5abe1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9520,6 +9520,13 @@ static u64 cpu_core_tag_color_read_u64(struct cgroup_subsys_state *css, struct c
 	return tg->core_tag_color;
 }
 
+#ifdef CONFIG_SCHED_DEBUG
+static u64 cpu_core_group_cookie_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
+{
+	return cpu_core_get_group_cookie(css_tg(css));
+}
+#endif
+
 struct write_core_tag {
 	struct cgroup_subsys_state *css;
 	unsigned long cookie;
@@ -9695,6 +9702,14 @@ static struct cftype cpu_legacy_files[] = {
 		.read_u64 = cpu_core_tag_color_read_u64,
 		.write_u64 = cpu_core_tag_color_write_u64,
 	},
+#ifdef CONFIG_SCHED_DEBUG
+	/* Read the effective cookie (color+tag) of the group. */
+	{
+		.name = "core_group_cookie",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.read_u64 = cpu_core_group_cookie_read_u64,
+	},
+#endif
 #endif
 #ifdef CONFIG_UCLAMP_TASK_GROUP
 	{
@@ -9882,6 +9897,14 @@ static struct cftype cpu_files[] = {
 		.read_u64 = cpu_core_tag_color_read_u64,
 		.write_u64 = cpu_core_tag_color_write_u64,
 	},
+#ifdef CONFIG_SCHED_DEBUG
+	/* Read the effective cookie (color+tag) of the group. */
+	{
+		.name = "core_group_cookie",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.read_u64 = cpu_core_group_cookie_read_u64,
+	},
+#endif
 #endif
 #ifdef CONFIG_CFS_BANDWIDTH
 	{
-- 
2.29.0.rc1.297.gfa9743e501-goog