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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-rt-users@vger.kernel.org
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH RT] mm/page_alloc: Use migreate_disable() in drain_local_pages_wq()
Date: Fri, 20 Mar 2020 17:56:11 +0100
Message-ID: <20200320165611.clg7ynljztcd52fs@linutronix.de> (raw)

The drain_local_pages_wq() uses preempt_disable() to ensure that there
will be no CPU migration while drain_local_pages() is invoked which
might happen if the CPU is going down.
drain_local_pages() acquires a sleeping lock on RT which can not be
acquired with disabled preemption.

Use migrate_disable() instead of preempt_disable(): On RT it ensures
that the CPU won't go down and on !RT it is replaced with
preempt_disable().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 mm/page_alloc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 99a51dfed59c7..7df9930628c2b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2912,9 +2912,9 @@ static void drain_local_pages_wq(struct work_struct *work)
 	 * cpu which is allright but we also have to make sure to not move to
 	 * a different one.
 	 */
-	preempt_disable();
+	migrate_disable();
 	drain_local_pages(drain->zone);
-	preempt_enable();
+	migrate_enable();
 }
 
 /*
-- 
2.26.0.rc2

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