[PATCH v1 4/9] cgroup: rstat: add WARN_ON_ONCE() if flushing outside task context

From: Yosry Ahmed
Date: Tue Mar 28 2023 - 02:17:36 EST


rstat flushing is too expensive to perform in irq context.
The previous patch removed the only context that may invoke an rstat
flush from irq context, add a WARN_ON_ONCE() to detect future
violations, or those that we are not aware of.

Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
---
kernel/cgroup/rstat.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
index d3252b0416b6..c2571939139f 100644
--- a/kernel/cgroup/rstat.c
+++ b/kernel/cgroup/rstat.c
@@ -176,6 +176,8 @@ static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep)
{
int cpu;

+ /* rstat flushing is too expensive for irq context */
+ WARN_ON_ONCE(!in_task());
lockdep_assert_held(&cgroup_rstat_lock);

for_each_possible_cpu(cpu) {
--
2.40.0.348.gf938b09366-goog