linux-kernel - [PATCH RT 4/8] mm/memcontrol: Move misplaced local_unlock

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Message-Id: <20200306184052.332769343@goodmis.org>
Date:   Fri, 06 Mar 2020 13:40:39 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org,
        linux-rt-users <linux-rt-users@...r.kernel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        John Kacur <jkacur@...hat.com>,
        Julia Cartwright <julia@...com>,
        Daniel Wagner <wagi@...om.org>,
        Tom Zanussi <zanussi@...nel.org>,
        "Srivatsa S. Bhat" <srivatsa@...il.mit.edu>,
        Matt Fleming <matt@...eblueprint.co.uk>
Subject: [PATCH RT 4/8] mm/memcontrol: Move misplaced local_unlock_irqrestore()

4.19.106-rt45-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Matt Fleming <matt@...eblueprint.co.uk>

[ Upstream commit 071a1d6a6e14d0dec240a8c67b425140d7f92f6a ]

The comment about local_lock_irqsave() mentions just the counters and
css_put_many()'s callback just invokes a worker so it is safe to move the
unlock function after memcg_check_events() so css_put_many() can be invoked
without the lock acquired.

Cc: Daniel Wagner <wagi@...om.org>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
[bigeasy: rewrote the patch description]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 421ac74450f6..519528959eef 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6540,10 +6540,10 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 	mem_cgroup_charge_statistics(memcg, page, PageTransHuge(page),
 				     -nr_entries);
 	memcg_check_events(memcg, page);
+	local_unlock_irqrestore(event_lock, flags);
 
 	if (!mem_cgroup_is_root(memcg))
 		css_put_many(&memcg->css, nr_entries);
-	local_unlock_irqrestore(event_lock, flags);
 }
 
 /**
-- 
2.25.0