linux-kernel - Re: next-20241001: WARNING: at mm/list_lru.c:77 list_lru_del (mm/list_lru.c:212 mm/list

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Message-ID: <62a65418-2393-40ec-b462-151605a5efcf@stanley.mountain>
Date: Wed, 2 Oct 2024 14:28:15 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Naresh Kamboju <naresh.kamboju@...aro.org>,
	Kairui Song <kasong@...cent.com>
Cc: open list <linux-kernel@...r.kernel.org>, lkft-triage@...ts.linaro.org,
	Linux Regressions <regressions@...ts.linux.dev>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Anders Roxell <anders.roxell@...aro.org>
Subject: Re: next-20241001: WARNING: at mm/list_lru.c:77 list_lru_del
 (mm/list_lru.c:212 mm/list_lru.c:200)

On Wed, Oct 02, 2024 at 02:25:34PM +0300, Dan Carpenter wrote:
> On Wed, Oct 02, 2024 at 02:24:20PM +0300, Dan Carpenter wrote:
> > Let's add Kairui Song to the  CC list.
> > 
> > One simple thing is that we should add a READ_ONCE() to the comparison.  Naresh,
> > could you test the attached diff?  I don't know that it will fix it but it's
> > worth checking the easy stuff first.
> > 
> 
> Actually that's not right.  Let me write a different patch.

Try this one.

regards,
dan carpenter

diff --git a/mm/list_lru.c b/mm/list_lru.c
index 79c2d21504a2..2c429578ed31 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -65,6 +65,7 @@ lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
 		       bool irq, bool skip_empty)
 {
 	struct list_lru_one *l;
+	long nr_items;
 	rcu_read_lock();
 again:
 	l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
@@ -73,8 +74,9 @@ lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
 			spin_lock_irq(&l->lock);
 		else
 			spin_lock(&l->lock);
-		if (likely(READ_ONCE(l->nr_items) != LONG_MIN)) {
-			WARN_ON(l->nr_items < 0);
+		nr_items = READ_ONCE(l->nr_items);
+		if (likely(nr_items != LONG_MIN)) {
+			WARN_ON(nr_items < 0);
 			rcu_read_unlock();
 			return l;
 		}