[119/262] mm: page_alloc: use migrate_disable() in drain_local_pages_wq()

Commit Message

Andrew Morton Nov. 5, 2021, 8:40 p.m. UTC

From: Sebastian Andrzej Siewior <[e-mail]>
Subject: mm: page_alloc: use migrate_disable() in drain_local_pages_wq()

drain_local_pages_wq() disables preemption to avoid CPU migration during
CPU hotplug and can't use cpus_read_lock().

Using migrate_disable() works here, too.  The scheduler won't take the CPU
offline until the task left the migrate-disable section.  The problem with
disabled preemption here is that drain_local_pages() acquires locks which
are turned into sleeping locks on PREEMPT_RT and can't be acquired with
disabled preemption.

Use migrate_disable() in drain_local_pages_wq().

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Sebastian Andrzej Siewior <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/page_alloc.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Patch

--- a/mm/page_alloc.c~mm-page_alloc-use-migrate_disable-in-drain_local_pages_wq
+++ a/mm/page_alloc.c
@@ -3141,9 +3141,9 @@  static void drain_local_pages_wq(struct
 	 * cpu which is alright 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();
 }
 
 /*