Merge branch 'for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - cgroup.kill is added which implements atomic killing of the whole
   subtree.

   Down the line, this should be able to replace the multiple userland
   implementations of "keep killing till empty".

 - PSI can now be turned off at boot time to avoid overhead for
   configurations which don't care about PSI.

* 'for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: make per-cgroup pressure stall tracking configurable
  cgroup: Fix kernel-doc
  cgroup: inline cgroup_task_freeze()
  tests/cgroup: test cgroup.kill
  tests/cgroup: move cg_wait_for(), cg_prepare_for_wait()
  tests/cgroup: use cgroup.kill in cg_killall()
  docs/cgroup: add entry for cgroup.kill
  cgroup: introduce cgroup.kill

1 files changed, 17 insertions, 13 deletions

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 58b36d17a09a..1652f2bb54b7 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -148,6 +148,7 @@
 static int psi_bug __read_mostly;
 
 DEFINE_STATIC_KEY_FALSE(psi_disabled);
+DEFINE_STATIC_KEY_TRUE(psi_cgroups_enabled);
 
 #ifdef CONFIG_PSI_DEFAULT_DISABLED
 static bool psi_enable;
@@ -215,6 +216,9 @@ void __init psi_init(void)
 		return;
 	}
 
+	if (!cgroup_psi_enabled())
+		static_branch_disable(&psi_cgroups_enabled);
+
 	psi_period = jiffies_to_nsecs(PSI_FREQ);
 	group_init(&psi_system);
 }
@@ -748,23 +752,23 @@ static void psi_group_change(struct psi_group *group, int cpu,
 
 static struct psi_group *iterate_groups(struct task_struct *task, void **iter)
 {
+	if (*iter == &psi_system)
+		return NULL;
+
 #ifdef CONFIG_CGROUPS
-	struct cgroup *cgroup = NULL;
+	if (static_branch_likely(&psi_cgroups_enabled)) {
+		struct cgroup *cgroup = NULL;
 
-	if (!*iter)
-		cgroup = task->cgroups->dfl_cgrp;
-	else if (*iter == &psi_system)
-		return NULL;
-	else
-		cgroup = cgroup_parent(*iter);
+		if (!*iter)
+			cgroup = task->cgroups->dfl_cgrp;
+		else
+			cgroup = cgroup_parent(*iter);
 
-	if (cgroup && cgroup_parent(cgroup)) {
-		*iter = cgroup;
-		return cgroup_psi(cgroup);
+		if (cgroup && cgroup_parent(cgroup)) {
+			*iter = cgroup;
+			return cgroup_psi(cgroup);
+		}
 	}
-#else
-	if (*iter)
-		return NULL;
 #endif
 	*iter = &psi_system;
 	return &psi_system;