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authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2022-04-10 14:49:36 +0200
committerThomas Gleixner <tglx@linutronix.de>2022-04-13 21:32:21 +0200
commit75d8cce128c516fe6cf4b8683e8fe1a59e919902 (patch)
treec90aa58d0e8ae63b4915d5af63c63ebc499fb561 /lib/irq_poll.c
parentce522ba9ef7e2d9fb22a39eb3371c0c64e2a433e (diff)
downloadlwn-75d8cce128c516fe6cf4b8683e8fe1a59e919902.tar.gz
lwn-75d8cce128c516fe6cf4b8683e8fe1a59e919902.zip
lib/irq_poll: Prevent softirq pending leak 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. [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
Diffstat (limited to 'lib/irq_poll.c')
-rw-r--r--lib/irq_poll.c8
1 files 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;
}