4.2.8-ckt2 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
commit abc7e40c81d113ef4bacb556f0a77ca63ac81d85 upstream.
If a interrupt chip utilizes chip->buslock then free_irq() can
deadlock in the following way:
CPU0 CPU1
interrupt(X) (Shared or spurious)
free_irq(X) interrupt_thread(X)
chip_bus_lock(X)
irq_finalize_oneshot(X)
chip_bus_lock(X)
synchronize_irq(X)
synchronize_irq() waits for the interrupt thread to complete,
i.e. forever.
Solution is simple: Drop chip_bus_lock() before calling
synchronize_irq() as we do with the irq_desc lock. There is nothing to
be protected after the point where irq_desc lock has been released.
This adds chip_bus_lock/unlock() to the remove_irq() code path, but
that's actually correct in the case where remove_irq() is called on
such an interrupt. The current users of remove_irq() are not affected
as none of those interrupts is on a chip which requires buslock.
Reported-by: Fredrik Markström <fredrik.markstrom@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
kernel/irq/manage.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index f974485..aaec958 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1363,6 +1363,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
if (!desc)
return NULL;
+ chip_bus_lock(desc);
raw_spin_lock_irqsave(&desc->lock, flags);
/*
@@ -1376,7 +1377,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
if (!action) {
WARN(1, "Trying to free already-free IRQ %d\n", irq);
raw_spin_unlock_irqrestore(&desc->lock, flags);
-
+ chip_bus_sync_unlock(desc);
return NULL;
}
@@ -1403,6 +1404,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
#endif
raw_spin_unlock_irqrestore(&desc->lock, flags);
+ chip_bus_sync_unlock(desc);
unregister_handler_proc(irq, action);
@@ -1476,9 +1478,7 @@ void free_irq(unsigned int irq, void *dev_id)
desc->affinity_notify = NULL;
#endif
- chip_bus_lock(desc);
kfree(__free_irq(irq, dev_id));
- chip_bus_sync_unlock(desc);
}
EXPORT_SYMBOL(free_irq);
--
1.9.1
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