From: Sebastian Andrzej Siewior bigeasy@linutronix.de
[ Upstream commit 75d8cce128c516fe6cf4b8683e8fe1a59e919902 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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; }