[PATCH] mm/memcg: Only perform the debug checks on !PREEMPT_RT

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Shakeel Butt <shakeelb@google.com>
Cc: Cgroups <cgroups@vger.kernel.org>,
	"Linux MM" <linux-mm@kvack.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Johannes Weiner" <hannes@cmpxchg.org>,
	"Michal Hocko" <mhocko@kernel.org>,
	"Michal Koutný" <mkoutny@suse.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Vladimir Davydov" <vdavydov.dev@gmail.com>,
	"Waiman Long" <longman@redhat.com>,
	"Roman Gushchin" <guro@fb.com>
Subject: [PATCH] mm/memcg: Only perform the debug checks on !PREEMPT_RT
Date: Sat, 26 Feb 2022 00:01:47 +0100	[thread overview]
Message-ID: <Yhlf29/HqyNMOvGb@linutronix.de> (raw)
In-Reply-To: <CALvZod48Tp7i_BbA4Um57m989iuFU5kSvbzLhSOUt23_CiWmjw@mail.gmail.com>

On PREEMPT_RT interrupts and preemption is always enabled. The locking
function __memcg_stats_lock() always disabled preemptions. The recently
added checks need to performed only on !PREEMPT_RT where preemption and
disabled interrupts are used.

Please fold into:
	"Protect per-CPU counter by disabling preemption on PREEMPT_RT"

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---

Andrew, if this getting to confused at some point, I can fold it myself
and repost the whole lot. Whatever works best for your.

 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 73832cd1e9da4..63287fd03250b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -741,7 +741,7 @@ void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx,
 	 * interrupt context while other caller need to have disabled interrupt.
 	 */
 	__memcg_stats_lock();
-	if (IS_ENABLED(CONFIG_DEBUG_VM)) {
+	if (IS_ENABLED(CONFIG_DEBUG_VM) && !IS_ENABLED(CONFIG_PREEMPT_RT)) {
 		switch (idx) {
 		case NR_ANON_MAPPED:
 		case NR_FILE_MAPPED:
-- 
2.35.1

