[PATCH 3.4 084/125] genirq: Prevent chip buslock deadlock

From: lizf
Date: Wed Oct 12 2016 - 08:44:21 EST

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

3.4.113-rc1 review patch. If anyone has any objections, please let me know.


commit abc7e40c81d113ef4bacb556f0a77ca63ac81d85 upstream.

If a interrupt chip utilizes chip->buslock then free_irq() can
deadlock in the following way:

interrupt(X) (Shared or spurious)
free_irq(X) interrupt_thread(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 MarkstrÃm <fredrik.markstrom@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx>
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 9baa631..43e4342 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1181,6 +1181,7 @@ 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);

@@ -1194,7 +1195,7 @@ 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;

@@ -1223,6 +1224,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)

raw_spin_unlock_irqrestore(&desc->lock, flags);
+ chip_bus_sync_unlock(desc);

unregister_handler_proc(irq, action);

@@ -1296,9 +1298,7 @@ void free_irq(unsigned int irq, void *dev_id)
desc->affinity_notify = NULL;

- chip_bus_lock(desc);
kfree(__free_irq(irq, dev_id));
- chip_bus_sync_unlock(desc);