From: Peter Zijlstra <a.p.zijlstra@chello.nl>

Workqueue functions should not leak locks, assert so, printing the
last function ran.

Use macros in lockdep.h to avoid include dependency pains.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 include/linux/lockdep.h |    5 +++++
 kernel/workqueue.c      |   12 ++++++++++++
 2 files changed, 17 insertions(+)

diff -puN include/linux/lockdep.h~debug-workqueue-locking-sanity include/linux/lockdep.h
--- a/include/linux/lockdep.h~debug-workqueue-locking-sanity
+++ a/include/linux/lockdep.h
@@ -243,6 +243,8 @@ extern void lock_release(struct lockdep_
 
 # define INIT_LOCKDEP				.lockdep_recursion = 0,
 
+#define lockdep_depth(tsk)	((tsk)->lockdep_depth)
+
 #else /* !LOCKDEP */
 
 static inline void lockdep_off(void)
@@ -277,6 +279,9 @@ static inline int lockdep_internal(void)
  * The class key takes no space if lockdep is disabled:
  */
 struct lock_class_key { };
+
+#define lockdep_depth(tsk)	(0)
+
 #endif /* !LOCKDEP */
 
 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_GENERIC_HARDIRQS)
diff -puN kernel/workqueue.c~debug-workqueue-locking-sanity kernel/workqueue.c
--- a/kernel/workqueue.c~debug-workqueue-locking-sanity
+++ a/kernel/workqueue.c
@@ -29,6 +29,7 @@
 #include <linux/kthread.h>
 #include <linux/hardirq.h>
 #include <linux/mempolicy.h>
+#include <linux/kallsyms.h>
 
 /*
  * The per-CPU workqueue (if single thread, we always use the first
@@ -222,6 +223,17 @@ static void run_workqueue(struct cpu_wor
 		clear_bit(0, &work->pending);
 		f(data);
 
+		if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
+			printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
+					"%s/0x%08x/%d\n",
+					current->comm, preempt_count(),
+				       	current->pid);
+			printk(KERN_ERR "    last function: ");
+			print_symbol("%s\n", (unsigned long)f);
+			debug_show_held_locks(current);
+			dump_stack();
+		}
+
 		spin_lock_irqsave(&cwq->lock, flags);
 		cwq->remove_sequence++;
 		wake_up(&cwq->work_done);
_