From: Sebastian Andrzej Siewior <[email protected]>

commit 87a4ecd3c2abc634b10f600d7fab5fbafc544dca linux-rt-devel.

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 <[email protected]>
Signed-off-by: Paul Gortmaker <[email protected]>
---
 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 99a51dfed59c..7df9930628c2 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();
 }
 
 /*
-- 
2.7.4

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