[PATCH] setup_irq(): better mismatch debugging

When we get a mismatch between handlers on the same IRQ, all we get is "IRQ
handler type mismatch for IRQ n".  Let's print the name of the
presently-registered handler with which we got the mismatch.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 6879202afe9a..b385878c6e80 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -216,6 +216,7 @@ int setup_irq(unsigned int irq, struct irqaction *new)
 {
         struct irq_desc *desc = irq_desc + irq;
         struct irqaction *old, **p;
+        const char *old_name = NULL;
         unsigned long flags;
         int shared = 0;
 
@@ -255,8 +256,10 @@ int setup_irq(unsigned int irq, struct irqaction *new)
                  * set the trigger type must match.
                  */
                 if (!((old->flags & new->flags) & IRQF_SHARED) ||
-                    ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK))
+                    ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK)) {
+                        old_name = old->name;
                         goto mismatch;
+                }
 
 #if defined(CONFIG_IRQ_PER_CPU)
                 /* All handlers must agree on per-cpuness */
@@ -322,11 +325,13 @@ int setup_irq(unsigned int irq, struct irqaction *new)
         return 0;
 
 mismatch:
-        spin_unlock_irqrestore(&desc->lock, flags);
         if (!(new->flags & IRQF_PROBE_SHARED)) {
                 printk(KERN_ERR "IRQ handler type mismatch for IRQ %d\n", irq);
+                if (old_name)
+                        printk(KERN_ERR "current handler: %s\n", old_name);
                 dump_stack();
         }
+        spin_unlock_irqrestore(&desc->lock, flags);
         return -EBUSY;
 }