From: Ingo Molnar <mingo@elte.hu>

Teach special (recursive) locking code to the lock validator.  Has no effect
on non-lockdep kernels.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 include/linux/lockdep.h |    6 ++++++
 init/main.c             |    1 +
 kernel/irq/handle.c     |   16 ++++++++++++++++
 3 files changed, 23 insertions(+)

diff -puN include/linux/lockdep.h~lockdep-annotate-genirq include/linux/lockdep.h
--- a/include/linux/lockdep.h~lockdep-annotate-genirq
+++ a/include/linux/lockdep.h
@@ -271,6 +271,12 @@ static inline int lockdep_internal(void)
 struct lock_class_key { };
 #endif /* !LOCKDEP */
 
+#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_GENERIC_HARDIRQS)
+extern void early_init_irq_lock_class(void);
+#else
+# define early_init_irq_lock_class()		do { } while (0)
+#endif
+
 #ifdef CONFIG_TRACE_IRQFLAGS
 extern void early_boot_irqs_off(void);
 extern void early_boot_irqs_on(void);
diff -puN init/main.c~lockdep-annotate-genirq init/main.c
--- a/init/main.c~lockdep-annotate-genirq
+++ a/init/main.c
@@ -492,6 +492,7 @@ asmlinkage void __init start_kernel(void
 
 	local_irq_disable();
 	early_boot_irqs_off();
+	early_init_irq_lock_class();
 
 /*
  * Interrupts are still disabled. Do necessary setups, then
diff -puN kernel/irq/handle.c~lockdep-annotate-genirq kernel/irq/handle.c
--- a/kernel/irq/handle.c~lockdep-annotate-genirq
+++ a/kernel/irq/handle.c
@@ -231,3 +231,19 @@ out:
 	return 1;
 }
 
+#ifdef CONFIG_TRACE_IRQFLAGS
+
+/*
+ * lockdep: we want to handle all irq_desc locks as a single lock-class:
+ */
+static struct lock_class_key irq_desc_lock_class;
+
+void early_init_irq_lock_class(void)
+{
+	int i;
+
+	for (i = 0; i < NR_IRQS; i++)
+		lockdep_set_class(&irq_desc[i].lock, &irq_desc_lock_class);
+}
+
+#endif
_