The patch titled
Subject: lib/irq_poll: Add local_bh_disable() in irq_poll_cpu_dead()
has been added to the -mm tree. Its filename is
lib-irq_poll-add-local_bh_disable-in-irq_poll_cpu_dead.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/lib-irq_poll-add-local_bh_disable-in-irq_poll_cpu_dead.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/lib-irq_poll-add-local_bh_disable-in-irq_poll_cpu_dead.patch
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------------------------------------------------------
From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Subject: lib/irq_poll: Add local_bh_disable() in irq_poll_cpu_dead()
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.
[@linutronix.de: massaged changelog and comment]
Link: https://lkml.kernel.org/r/87k0bxgl27.ffs@tglx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/lib/irq_poll.c~lib-irq_poll-add-local_bh_disable-in-irq_poll_cpu_dead
+++ a/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;
}
_
Patches currently in -mm which might be from bigeasy@xxxxxxxxxxxxx are
lib-irq_poll-add-local_bh_disable-in-irq_poll_cpu_dead.patch
