irq: refactor and clean up the free_irq() code flow

Impact: cleanup

- separate out the loop from the actual freeing logic, this wins us
  two indentation levels allowing a number of followup prettifications

- turn the WARN_ON() into a more informative WARN().

- clean up the comments and the code flow some more

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 8f4bc61..7a954b8 100644 (file)
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -575,72 +575,79 @@ int setup_irq(unsigned int irq, struct irqaction *act)
 void free_irq(unsigned int irq, void *dev_id)
 {
        struct irq_desc *desc = irq_to_desc(irq);
-       struct irqaction **p;
+       struct irqaction *action, **p, **pp;
        unsigned long flags;
 
-       WARN_ON(in_interrupt());
+       WARN(in_interrupt(), "Trying to free IRQ %d from IRQ context!\n", irq);
 
        if (!desc)
                return;
 
        spin_lock_irqsave(&desc->lock, flags);
+
+       /*
+        * There can be multiple actions per IRQ descriptor, find the right
+        * one based on the dev_id:
+        */
        p = &desc->action;
        for (;;) {
-               struct irqaction *action = *p;
+               action = *p;
+               pp = p;
+
+               if (!action) {
+                       WARN(1, "Trying to free already-free IRQ %d\n", irq);
+                       spin_unlock_irqrestore(&desc->lock, flags);
+
+                       return;
+               }
 
-               if (action) {
-                       struct irqaction **pp = p;
+               p = &action->next;
+               if (action->dev_id != dev_id)
+                       continue;
 
-                       p = &action->next;
-                       if (action->dev_id != dev_id)
-                               continue;
+               break;
+       }
 
-                       /* Found it - now remove it from the list of entries */
-                       *pp = action->next;
+       /* Found it - now remove it from the list of entries: */
+       *pp = action->next;
 
-                       /* Currently used only by UML, might disappear one day.*/
+       /* Currently used only by UML, might disappear one day: */
 #ifdef CONFIG_IRQ_RELEASE_METHOD
-                       if (desc->chip->release)
-                               desc->chip->release(irq, dev_id);
+       if (desc->chip->release)
+               desc->chip->release(irq, dev_id);
 #endif
 
-                       if (!desc->action) {
-                               desc->status |= IRQ_DISABLED;
-                               if (desc->chip->shutdown)
-                                       desc->chip->shutdown(irq);
-                               else
-                                       desc->chip->disable(irq);
-                       }
-                       spin_unlock_irqrestore(&desc->lock, flags);
-                       unregister_handler_proc(irq, action);
+       /* If this was the last handler, shut down the IRQ line: */
+       if (!desc->action) {
+               desc->status |= IRQ_DISABLED;
+               if (desc->chip->shutdown)
+                       desc->chip->shutdown(irq);
+               else
+                       desc->chip->disable(irq);
+       }
+       spin_unlock_irqrestore(&desc->lock, flags);
+
+       unregister_handler_proc(irq, action);
+
+       /* Make sure it's not being used on another CPU: */
+       synchronize_irq(irq);
 
-                       /* Make sure it's not being used on another CPU */
-                       synchronize_irq(irq);
-#ifdef CONFIG_DEBUG_SHIRQ
-                       /*
-                        * It's a shared IRQ -- the driver ought to be
-                        * prepared for it to happen even now it's
-                        * being freed, so let's make sure....  We do
-                        * this after actually deregistering it, to
-                        * make sure that a 'real' IRQ doesn't run in
-                        * parallel with our fake
-                        */
-                       if (action->flags & IRQF_SHARED) {
-                               local_irq_save(flags);
-                               action->handler(irq, dev_id);
-                               local_irq_restore(flags);
-                       }
-#endif
-                       kfree(action);
-                       return;
-               }
-               printk(KERN_ERR "Trying to free already-free IRQ %d\n", irq);
 #ifdef CONFIG_DEBUG_SHIRQ
-               dump_stack();
-#endif
-               spin_unlock_irqrestore(&desc->lock, flags);
-               return;
+       /*
+        * It's a shared IRQ -- the driver ought to be prepared for an IRQ
+        * event to happen even now it's being freed, so let's make sure that
+        * is so by doing an extra call to the handler ....
+        *
+        * ( We do this after actually deregistering it, to make sure that a
+        *   'real' IRQ doesn't run in * parallel with our fake. )
+        */
+       if (action->flags & IRQF_SHARED) {
+               local_irq_save(flags);
+               action->handler(irq, dev_id);
+               local_irq_restore(flags);
        }
+#endif
+       kfree(action);
 }
 EXPORT_SYMBOL(free_irq);