From: Thomas Gleixner <>

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:

CPU0                            CPU1
                                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 Markström <>
Signed-off-by: Thomas Gleixner <>
Signed-off-by: Zefan Li <>
 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);

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