With
	CONFIG_SMP=y
	CONFIG_PREEMPT=y
	CONFIG_LOCKDEP=y
	CONFIG_DEBUG_LOCK_ALLOC=y
	# CONFIG_PROVE_LOCKING is not set
spin_unlock_irqrestore() goes through lockdep but spin_lock_irqsave() doesn't.
Apparently, bad things happen.
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
  * not re-enabled during lock-acquire (which the preempt-spin-ops do):
  */
 #if !defined(CONFIG_PREEMPT) || !defined(CONFIG_SMP) || \
-       defined(CONFIG_PROVE_LOCKING)
+       defined(CONFIG_DEBUG_LOCK_ALLOC)
 
 void __lockfunc _read_lock(rwlock_t *lock)
 {