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>

1 files changed, 54 insertions, 47 deletions

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 8f4bc61f0df9..7a954b860c07 100644
--- 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);