From 00d027966733f5dab7f5cbacbc3428fd079cff5f Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Fri, 15 Oct 2021 23:09:33 +0200 Subject: [PATCH 028/166] 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(). Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20211015210933.viw6rjvo64qtqxn4@linutronix.de --- mm/page_alloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) Index: linux-5.15.32-rt39/mm/page_alloc.c =================================================================== --- linux-5.15.32-rt39.orig/mm/page_alloc.c +++ linux-5.15.32-rt39/mm/page_alloc.c @@ -3149,9 +3149,9 @@ 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(); } /*