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lib/irq_poll: Prevent softirq pending leak in irq_poll_cpu_dead()

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irq_poll_cpu_dead() pulls the blk_cpu_iopoll backlog from the dead CPU and
raises the POLL softirq with __raise_softirq_irqoff() on the CPU it is
running on. That just sets the bit in the pending softirq mask.

This means the handling of the softirq is delayed until the next interrupt
or a local_bh_disable/enable() pair. As a consequence the CPU on which this
code runs can reach idle with the POLL softirq pending, which triggers a
warning in the NOHZ idle code.

Add a local_bh_disable/enable() pair around the interrupts disabled section
in irq_poll_cpu_dead(). local_bh_enable will handle the pending softirq.

[tglx: Massaged changelog and comment]

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/87k0bxgl27.ffs@tglx
This commit is contained in:
Sebastian Andrzej Siewior 2022-04-10 14:49:36 +02:00 committed by Thomas Gleixner
parent ce522ba9ef
commit 75d8cce128
1 changed files with 6 additions and 2 deletions
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8
lib/irq_poll.c
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@ -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;
}