Index: sys/ktr.h
===================================================================
RCS file: /home/iedowse/CVS/src/sys/sys/ktr.h,v
retrieving revision 1.18
diff -u -r1.18 ktr.h
--- sys/ktr.h	23 Jun 2002 00:38:04 -0000	1.18
+++ sys/ktr.h	22 Aug 2002 19:24:23 -0000
@@ -71,7 +71,8 @@
 #define KTR_VM		0x00100000		/* The virtual memory system */
 #define KTR_WITNESS	0x00200000
 #define	KTR_RUNQ	0x00400000		/* Run queue */
-#define	KTR_ALL		0x007fffff
+#define	KTR_CONTENTION	0x00800000		/* Lock contention */
+#define	KTR_ALL		0x00ffffff
 
 /*
  * Trace classes which can be assigned to particular use at compile time
Index: sys/lock.h
===================================================================
RCS file: /home/iedowse/CVS/src/sys/sys/lock.h,v
retrieving revision 1.44
diff -u -r1.44 lock.h
--- sys/lock.h	21 Apr 2002 10:42:15 -0000	1.44
+++ sys/lock.h	22 Aug 2002 19:25:43 -0000
@@ -212,6 +212,8 @@
 int	witness_list(struct thread *);
 int	witness_sleep(int, struct lock_object *, const char *, int);
 void	witness_assert(struct lock_object *, int, const char *, int);
+int	witness_line(struct lock_object *);
+const char *witness_file(struct lock_object *);
 
 #ifdef	WITNESS
 #define	WITNESS_INIT(lock)						\
@@ -245,6 +247,12 @@
 #define	WITNESS_RESTORE(lock, n) 					\
 	witness_restore((lock), __CONCAT(n, __wf), __CONCAT(n, __wl))
 
+#define	WITNESS_FILE(lock) 						\
+	witness_file(lock)
+
+#define	WITNESS_LINE(lock) 						\
+	witness_line(lock)
+
 #else	/* WITNESS */
 #define	WITNESS_INIT(lock)	((lock)->lo_flags |= LO_INITIALIZED)
 #define	WITNESS_DESTROY(lock)	((lock)->lo_flags &= ~LO_INITIALIZED)
@@ -256,6 +264,8 @@
 #define	WITNESS_SAVE_DECL(n)
 #define	WITNESS_SAVE(lock, n)
 #define	WITNESS_RESTORE(lock, n)
+#define	WITNESS_FILE(lock) ("")
+#define	WITNESS_LINE(lock) (0)
 #endif	/* WITNESS */
 
 #endif	/* _KERNEL */
Index: kern/kern_mutex.c
===================================================================
RCS file: /home/iedowse/CVS/src/sys/kern/kern_mutex.c,v
retrieving revision 1.104
diff -u -r1.104 kern_mutex.c
--- kern/kern_mutex.c	27 Jul 2002 16:54:23 -0000	1.104
+++ kern/kern_mutex.c	22 Aug 2002 19:24:23 -0000
@@ -471,6 +471,7 @@
 #if defined(SMP) && defined(ADAPTIVE_MUTEXES)
 	struct thread *owner;
 #endif
+	int logged = 0;
 
 	if ((m->mtx_lock & MTX_FLAGMASK) == (uintptr_t)td) {
 		m->mtx_recurse++;
@@ -589,6 +590,15 @@
 				TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_blkq);
 		}
 
+		if (!logged) {
+			CTR6(KTR_CONTENTION,
+			    "contention: %p at %s:%d wants %s, taken by %s:%d",
+			    td, file, line, m->mtx_object.lo_name,
+			    WITNESS_FILE(&m->mtx_object),
+			    WITNESS_LINE(&m->mtx_object));
+			logged = 1;
+		}
+
 		/*
 		 * Save who we're blocked on.
 		 */
@@ -613,6 +623,11 @@
 		mtx_unlock_spin(&sched_lock);
 	}
 
+	if (logged) {
+		CTR4(KTR_CONTENTION,
+		    "contention end: %s acquired by %p at %s:%d",
+		    m->mtx_object.lo_name, td, file, line);
+	}
 	return;
 }
 
Index: kern/subr_witness.c
===================================================================
RCS file: /home/iedowse/CVS/src/sys/kern/subr_witness.c,v
retrieving revision 1.122
diff -u -r1.122 subr_witness.c
--- kern/subr_witness.c	15 Jul 2002 02:03:17 -0000	1.122
+++ kern/subr_witness.c	22 Aug 2002 19:25:14 -0000
@@ -929,6 +929,30 @@
 	return (n);
 }
 
+const char *
+witness_file(struct lock_object *lock)
+{
+	struct witness *w;
+
+	if (witness_cold || witness_dead || lock->lo_witness == NULL ||
+	    panicstr != NULL)
+		return (NULL);
+	w = lock->lo_witness;
+	return (w->w_file);
+}
+
+int
+witness_line(struct lock_object *lock)
+{
+	struct witness *w;
+
+	if (witness_cold || witness_dead || lock->lo_witness == NULL ||
+	    panicstr != NULL)
+		return (0);
+	w = lock->lo_witness;
+	return (w->w_line);
+}
+
 static struct witness *
 enroll(const char *description, struct lock_class *lock_class)
 {