[PATCH v6 1/3] genirq: enhance error recovery code in free irq

[Ben Luo]

__free_irq()/__free_percpu_irq() need to return if called from IRQ
context because the interrupt handler loop runs with desc->lock dropped
and dev_id can be subject to load and store tearing. Also move WARNs
out of lock region and print out dev_id to help debugging.

Signed-off-by: Ben Luo <luoben@xxxxxxxxxxxxxxxxx>
---
 kernel/irq/manage.c | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index e8f7f17..10ec3e9 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1690,7 +1690,10 @@ static struct irqaction *__free_irq(struct irq_desc *desc, void *dev_id)
 	struct irqaction *action, **action_ptr;
 	unsigned long flags;
 
-	WARN(in_interrupt(), "Trying to free IRQ %d from IRQ context!\n", irq);
+	if (WARN(in_interrupt(),
+		 "Trying to free IRQ %d (dev_id %p) from IRQ context!\n",
+		 irq, dev_id))
+		return NULL;
 
 	mutex_lock(&desc->request_mutex);
 	chip_bus_lock(desc);
@@ -1705,10 +1708,11 @@ static struct irqaction *__free_irq(struct irq_desc *desc, void *dev_id)
 		action = *action_ptr;
 
 		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);
 			mutex_unlock(&desc->request_mutex);
+			WARN(1, "Trying to free already-free IRQ %d (dev_id %p)\n",
+			     irq, dev_id);
 			return NULL;
 		}
 
@@ -2286,7 +2290,10 @@ static struct irqaction *__free_percpu_irq(unsigned int irq, void __percpu *dev_
 	struct irqaction *action;
 	unsigned long flags;
 
-	WARN(in_interrupt(), "Trying to free IRQ %d from IRQ context!\n", irq);
+	if (WARN(in_interrupt(),
+		 "Trying to free IRQ %d (dev_id %p) from IRQ context!\n",
+		 irq, dev_id))
+		return NULL;
 
 	if (!desc)
 		return NULL;
@@ -2295,14 +2302,17 @@ static struct irqaction *__free_percpu_irq(unsigned int irq, void __percpu *dev_
 
 	action = desc->action;
 	if (!action || action->percpu_dev_id != dev_id) {
-		WARN(1, "Trying to free already-free IRQ %d\n", irq);
-		goto bad;
+		raw_spin_unlock_irqrestore(&desc->lock, flags);
+		WARN(1, "Trying to free already-free IRQ (dev_id %p) %d\n",
+		     dev_id, irq);
+		return NULL;
 	}
 
 	if (!cpumask_empty(desc->percpu_enabled)) {
-		WARN(1, "percpu IRQ %d still enabled on CPU%d!\n",
-		     irq, cpumask_first(desc->percpu_enabled));
-		goto bad;
+		raw_spin_unlock_irqrestore(&desc->lock, flags);
+		WARN(1, "percpu IRQ %d (dev_id %p) still enabled on CPU%d!\n",
+		     irq, dev_id, cpumask_first(desc->percpu_enabled));
+		return NULL;
 	}
 
 	/* Found it - now remove it from the list of entries: */
@@ -2317,10 +2327,6 @@ static struct irqaction *__free_percpu_irq(unsigned int irq, void __percpu *dev_
 	irq_chip_pm_put(&desc->irq_data);
 	module_put(desc->owner);
 	return action;
-
-bad:
-	raw_spin_unlock_irqrestore(&desc->lock, flags);
-	return NULL;
 }
 
 /**
-- 
1.8.3.1