linux-kernel - [PATCH RT 1/3] mm/memcontrol: Disable preemption in __mod_memcg_lruvec

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Message-Id: <46fc7bbf28dfbafd2f6e87b736458c4ba060728c.1605633581.git.zanussi@kernel.org>
Date:   Tue, 17 Nov 2020 11:19:46 -0600
From:   zanussi@...nel.org
To:     LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        John Kacur <jkacur@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Daniel Wagner <wagi@...om.org>,
        Clark Williams <williams@...hat.com>,
        Pavel Machek <pavel@...x.de>, Tom Zanussi <zanussi@...nel.org>
Cc:     stable-rt@...r.kernel.org
Subject: [PATCH RT 1/3] mm/memcontrol: Disable preemption in __mod_memcg_lruvec_state()

From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

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@...r.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Tom Zanussi <zanussi@...nel.org>

 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