The patch titled
Fix misrouted interrupts deadlocks
has been added to the -mm tree. Its filename is
fix-misrouted-interrupts-deadlocks.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: Fix misrouted interrupts deadlocks
From: Pavel Emelianov <xemul@xxxxxxxxxx>
While testing kernel on machine with "irqpoll" option I've caught such a
lockup:
__do_IRQ()
spin_lock(&desc->lock);
desc->chip->ack(); /* IRQ is ACKed */
note_interrupt()
misrouted_irq()
handle_IRQ_event()
if (...)
local_irq_enable_in_hardirq();
/* interrupts are enabled from now */
...
__do_IRQ() /* same IRQ we've started from */
spin_lock(&desc->lock); /* LOCKUP */
Looking at misrouted_irq() code I've found that a potential deadlock like
this can also take place:
1CPU:
__do_IRQ()
spin_lock(&desc->lock); /* irq = A */
misrouted_irq()
for (i = 1; i < NR_IRQS; i++) {
spin_lock(&desc->lock); /* irq = B */
if (desc->status & IRQ_INPROGRESS) {
2CPU:
__do_IRQ()
spin_lock(&desc->lock); /* irq = B */
misrouted_irq()
for (i = 1; i < NR_IRQS; i++) {
spin_lock(&desc->lock); /* irq = A */
if (desc->status & IRQ_INPROGRESS) {
As the second lock on both CPUs is taken before checking that this irq is
being handled in another processor this may cause a deadlock. This issue
is only theoretical.
I propose the attached patch to fix booth problems: when trying to handle
misrouted IRQ active desc->lock may be unlocked.
Acked-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
kernel/irq/spurious.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff -puN kernel/irq/spurious.c~fix-misrouted-interrupts-deadlocks kernel/irq/spurious.c
--- a/kernel/irq/spurious.c~fix-misrouted-interrupts-deadlocks
+++ a/kernel/irq/spurious.c
@@ -147,7 +147,11 @@ void note_interrupt(unsigned int irq, st
if (unlikely(irqfixup)) {
/* Don't punish working computers */
if ((irqfixup == 2 && irq == 0) || action_ret == IRQ_NONE) {
- int ok = misrouted_irq(irq);
+ int ok;
+
+ spin_unlock(&desc->lock);
+ ok = misrouted_irq(irq);
+ spin_lock(&desc->lock);
if (action_ret == IRQ_NONE)
desc->irqs_unhandled -= ok;
}
_
Patches currently in -mm which might be from xemul@xxxxxxxxxx are
fix-misrouted-interrupts-deadlocks.patch
-
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