linux-kernel - [GIT pull] core/core for 5.19-rc1

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Date:   Mon, 23 May 2022 10:02:03 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [GIT pull] core/core for 5.19-rc1

Linus,

please pull the latest core/core branch from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-core-2022-05-23

up to:  75d8cce128c5: lib/irq_poll: Prevent softirq pending leak in irq_poll_cpu_dead()


A single update for irqpoll:

  - Ensure that a raised soft interrupt is handled after pulling the
    blk_cpu_iopoll backlog from a unplugged CPU. This prevents that the CPU
    which runs that code reaches idle with soft interrupts pending.

Thanks,

	tglx

------------------>
Sebastian Andrzej Siewior (1):
      lib/irq_poll: Prevent softirq pending leak in irq_poll_cpu_dead()


 lib/irq_poll.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/lib/irq_poll.c b/lib/irq_poll.c
index 2f17b488d58e..2d5329a42105 100644
--- a/lib/irq_poll.c
+++ b/lib/irq_poll.c
@@ -188,14 +188,18 @@ EXPORT_SYMBOL(irq_poll_init);
 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
+	 * If a CPU goes away, splice its entries to the current CPU and
+	 * set the POLL softirq bit. The local_bh_disable()/enable() pair
+	 * ensures that it is handled. Otherwise the current CPU could
+	 * reach idle with the POLL softirq pending.
 	 */
+	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;
 }