Track lock waittime - that is the time spend waiting on lock acquisition.

/proc/lock_waittime - starts with the same three colums as lock_contentions:

  <class name> <(write) contentions> <read contentions>

After that come two times four more columns:

  <nr> <min> <max> <total>

for both (write) contentions and read contentions. Times are in 1e-9 seconds.
Writing a 0 to the file clears the stats.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 include/linux/lockdep.h |   15 ++++++++
 kernel/lockdep.c        |   79 +++++++++++++++++++++++++++++++++++++++++++++
 kernel/lockdep_proc.c   |   84 ++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/mutex.c          |    1 
 4 files changed, 179 insertions(+)

Index: linux-2.6/include/linux/lockdep.h
===================================================================
--- linux-2.6.orig/include/linux/lockdep.h	2007-05-22 23:46:47.000000000 +0200
+++ linux-2.6/include/linux/lockdep.h	2007-05-22 23:46:53.000000000 +0200
@@ -77,6 +77,13 @@ struct lock_contention_point {
 	atomic_t count;
 };
 
+struct lock_time {
+	raw_spinlock_t lock;
+	unsigned long long min, max;
+	unsigned long long total;
+	unsigned long nr;
+};
+
 /*
  * The lock-class itself:
  */
@@ -125,6 +132,8 @@ struct lock_class {
 	atomic_t			read_contentions;
 	atomic_t			write_contentions;
 	struct lock_contention_point	contention_point[4];
+	struct lock_time		read_waittime;
+	struct lock_time		write_waittime;
 #endif
 };
 
@@ -177,6 +186,9 @@ struct held_lock {
 	unsigned long			acquire_ip;
 	struct lockdep_map		*instance;
 
+#ifdef CONFIG_LOCK_STAT
+	unsigned long long 		waittime_stamp;
+#endif
 	/*
 	 * The lock-stack is unified in that the lock chains of interrupt
 	 * contexts nest ontop of process context chains, but we 'separate'
@@ -296,18 +308,21 @@ struct lock_class_key { };
 #ifdef CONFIG_LOCK_STAT
 
 extern void lock_contended(struct lockdep_map *lock, unsigned long ip);
+extern void lock_acquired(struct ...
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