irq: Track the owner of irq descriptor

Interrupt descriptors can be allocated from modules. The interrupts
are used by other modules, but we have no refcount on the module which
provides the interrupts and there is no way to establish one on the
device level as the interrupt using module is agnostic to the fact
that the interrupt is provided by a module rather than by some builtin
interrupt controller.

To prevent removal of the interrupt providing module, we can track the
owner of the interrupt descriptor, which also provides the relevant
irq chip functions in the irq descriptor.

request/setup_irq() can now acquire a refcount on the owner module to
prevent unloading. free_irq() drops the refcount.

Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Link: http://lkml.kernel.org/r/20110711101731.GA13804@Chamillionaire.breakpoint.cc
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 13 insertions, 4 deletions

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 3f9cd4799da7..2e9425889fa8 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -883,6 +883,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 
 	if (desc->irq_data.chip == &no_irq_chip)
 		return -ENOSYS;
+	if (!try_module_get(desc->owner))
+		return -ENODEV;
 	/*
 	 * Some drivers like serial.c use request_irq() heavily,
 	 * so we have to be careful not to interfere with a
@@ -906,8 +908,10 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 	 */
 	nested = irq_settings_is_nested_thread(desc);
 	if (nested) {
-		if (!new->thread_fn)
-			return -EINVAL;
+		if (!new->thread_fn) {
+			ret = -EINVAL;
+			goto out_mput;
+		}
 		/*
 		 * Replace the primary handler which was provided from
 		 * the driver for non nested interrupt handling by the
@@ -929,8 +933,10 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 
 		t = kthread_create(irq_thread, new, "irq/%d-%s", irq,
 				   new->name);
-		if (IS_ERR(t))
-			return PTR_ERR(t);
+		if (IS_ERR(t)) {
+			ret = PTR_ERR(t);
+			goto out_mput;
+		}
 		/*
 		 * We keep the reference to the task struct even if
 		 * the thread dies to avoid that the interrupt code
@@ -1095,6 +1101,8 @@ out_thread:
 			kthread_stop(t);
 		put_task_struct(t);
 	}
+out_mput:
+	module_put(desc->owner);
 	return ret;
 }
 
@@ -1203,6 +1211,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 		put_task_struct(action->thread);
 	}
 
+	module_put(desc->owner);
 	return action;
 }