[PATCH RT 1/3] mm/memcontrol: Disable preemption in __mod_memcg_lruvec_state()

[zanussi]

From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

v4.19.152-rt66-rc1 stable review patch.
If anyone has any objections, please let me know.

-----------


[ Upstream commit 74858f0d38a8d3c069a0745ff53ae084c8e7cabb ]

The callers expect disabled preemption/interrupts while invoking
__mod_memcg_lruvec_state(). This works mainline because a lock of
somekind is acquired.

Use preempt_disable_rt() where per-CPU variables are accessed and a
stable pointer is expected. This is also done in __mod_zone_page_state()
for the same reason.

Cc: stable-rt@xxxxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Tom Zanussi <zanussi@xxxxxxxxxx>

 Conflicts:
	mm/memcontrol.c
---
 include/linux/memcontrol.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index cc6b6532eb56..dbb2c4e27277 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -665,6 +665,7 @@ static inline void __mod_lruvec_state(struct lruvec *lruvec,
 
 	pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
 
+	preempt_disable_rt();
 	/* Update memcg */
 	__mod_memcg_state(pn->memcg, idx, val);
 
@@ -675,6 +676,7 @@ static inline void __mod_lruvec_state(struct lruvec *lruvec,
 		x = 0;
 	}
 	__this_cpu_write(pn->lruvec_stat_cpu->count[idx], x);
+	preempt_enable_rt();
 }
 
 static inline void mod_lruvec_state(struct lruvec *lruvec,
-- 
2.17.1