From 42a7c2c1d703a87011dbf5300a4a91f5217ffb2f Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 2 Apr 2020 21:16:30 +0200
Subject: [PATCH] irq_poll: Add local_bh_disable() in cpu_dead notifier

References: SLE Realtime Extension
Patch-mainline: Queued in subsystem maintainer repository
Git-commit: e097e0cb12375ba7e27ac416811775fe7edfda99
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git

__raise_softirq_irqoff() adds a bit to the pending sofirq mask and this
is it. The softirq won't be handled in a deterministic way but randomly
when an interrupt fires and handles the softirq in its irq_exit() routine or
if something randomly checks and handles pending softirqs in the call
chain before the CPU goes idle.

Add a local_bh_disable/enable() around the IRQ-off section which will
handle pending softirqs.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/all/YgJ%2FXWVxxWDVBBVA@linutronix.de
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 lib/irq_poll.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/irq_poll.c b/lib/irq_poll.c
index 2f17b488d58e..2b9f797642f6 100644
--- a/lib/irq_poll.c
+++ b/lib/irq_poll.c
@@ -191,11 +191,13 @@ static int irq_poll_cpu_dead(unsigned int cpu)
 	 * If a CPU goes away, splice its entries to the current CPU
 	 * and trigger a run of the softirq
 	 */
+	local_bh_disable();
 	local_irq_disable();
 	list_splice_init(&per_cpu(blk_cpu_iopoll, cpu),
 			 this_cpu_ptr(&blk_cpu_iopoll));
 	__raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
 	local_irq_enable();
+	local_bh_enable();
 
 	return 0;
 }