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Subject[GIT pull] irq fix for 4.13
Linus,

please pull the latest irq-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq-urgent-for-linus

Fix the fallout from reworking the locking and resource management in
request/free_irq().

Thanks,

tglx

------------------>
Thomas Gleixner (1):
genirq: Keep chip buslock across irq_request/release_resources()


kernel/irq/manage.c | 63 ++++++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 53 insertions(+), 10 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 5624b2dd6b58..1d1a5b945ab4 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1090,6 +1090,16 @@ setup_irq_thread(struct irqaction *new, unsigned int irq, bool secondary)
/*
* Internal function to register an irqaction - typically used to
* allocate special interrupts that are part of the architecture.
+ *
+ * Locking rules:
+ *
+ * desc->request_mutex Provides serialization against a concurrent free_irq()
+ * chip_bus_lock Provides serialization for slow bus operations
+ * desc->lock Provides serialization against hard interrupts
+ *
+ * chip_bus_lock and desc->lock are sufficient for all other management and
+ * interrupt related functions. desc->request_mutex solely serializes
+ * request/free_irq().
*/
static int
__setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
@@ -1167,20 +1177,35 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
if (desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)
new->flags &= ~IRQF_ONESHOT;

+ /*
+ * Protects against a concurrent __free_irq() call which might wait
+ * for synchronize_irq() to complete without holding the optional
+ * chip bus lock and desc->lock.
+ */
mutex_lock(&desc->request_mutex);
+
+ /*
+ * Acquire bus lock as the irq_request_resources() callback below
+ * might rely on the serialization or the magic power management
+ * functions which are abusing the irq_bus_lock() callback,
+ */
+ chip_bus_lock(desc);
+
+ /* First installed action requests resources. */
if (!desc->action) {
ret = irq_request_resources(desc);
if (ret) {
pr_err("Failed to request resources for %s (irq %d) on irqchip %s\n",
new->name, irq, desc->irq_data.chip->name);
- goto out_mutex;
+ goto out_bus_unlock;
}
}

- chip_bus_lock(desc);
-
/*
* The following block of code has to be executed atomically
+ * protected against a concurrent interrupt and any of the other
+ * management calls which are not serialized via
+ * desc->request_mutex or the optional bus lock.
*/
raw_spin_lock_irqsave(&desc->lock, flags);
old_ptr = &desc->action;
@@ -1286,10 +1311,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
ret = __irq_set_trigger(desc,
new->flags & IRQF_TRIGGER_MASK);

- if (ret) {
- irq_release_resources(desc);
+ if (ret)
goto out_unlock;
- }
}

desc->istate &= ~(IRQS_AUTODETECT | IRQS_SPURIOUS_DISABLED | \
@@ -1385,12 +1408,10 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
out_unlock:
raw_spin_unlock_irqrestore(&desc->lock, flags);

- chip_bus_sync_unlock(desc);
-
if (!desc->action)
irq_release_resources(desc);
-
-out_mutex:
+out_bus_unlock:
+ chip_bus_sync_unlock(desc);
mutex_unlock(&desc->request_mutex);

out_thread:
@@ -1472,6 +1493,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
WARN(1, "Trying to free already-free IRQ %d\n", irq);
raw_spin_unlock_irqrestore(&desc->lock, flags);
chip_bus_sync_unlock(desc);
+ mutex_unlock(&desc->request_mutex);
return NULL;
}

@@ -1498,6 +1520,20 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
#endif

raw_spin_unlock_irqrestore(&desc->lock, flags);
+ /*
+ * Drop bus_lock here so the changes which were done in the chip
+ * callbacks above are synced out to the irq chips which hang
+ * behind a slow bus (I2C, SPI) before calling synchronize_irq().
+ *
+ * Aside of that the bus_lock can also be taken from the threaded
+ * handler in irq_finalize_oneshot() which results in a deadlock
+ * because synchronize_irq() would wait forever for the thread to
+ * complete, which is blocked on the bus lock.
+ *
+ * The still held desc->request_mutex() protects against a
+ * concurrent request_irq() of this irq so the release of resources
+ * and timing data is properly serialized.
+ */
chip_bus_sync_unlock(desc);

unregister_handler_proc(irq, action);
@@ -1530,8 +1566,15 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
}
}

+ /* Last action releases resources */
if (!desc->action) {
+ /*
+ * Reaquire bus lock as irq_release_resources() might
+ * require it to deallocate resources over the slow bus.
+ */
+ chip_bus_lock(desc);
irq_release_resources(desc);
+ chip_bus_sync_unlock(desc);
irq_remove_timings(desc);
}

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