Add two new function pointers 'lc_lock' and 'lc_unlock' to lock classes.

These functions are intended to be used to drop a lock and then reacquire
it when doing an sleep such as msleep(9).  Both functions accept a
'struct lock_object *' as their first parameter.  The 'lc_unlock' function
returns an integer that is then passed as the second paramter to the
subsequent 'lc_lock' function.  This can be used to communicate state.
For example, sx locks and rwlocks use this to indicate if the lock was
share/read locked vs exclusive/write locked.

Currently, spin mutexes and lockmgr locks do not provide working lc_lock
and lc_unlock functions.

1 files changed, 19 insertions, 3 deletions

diff --git a/sys/kern/kern_lock.c b/sys/kern/kern_lock.c
index 8533836..02254a4 100644
--- a/sys/kern/kern_lock.c
+++ b/sys/kern/kern_lock.c
@@ -64,22 +64,38 @@ __FBSDID("$FreeBSD$");
 #include <ddb/ddb.h>
 static void	db_show_lockmgr(struct lock_object *lock);
 #endif
-
+static void	lock_lockmgr(struct lock_object *lock, int how);
+static int	unlock_lockmgr(struct lock_object *lock);
 
 struct lock_class lock_class_lockmgr = {
 	.lc_name = "lockmgr",
 	.lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE,
 #ifdef DDB
-	.lc_ddb_show = db_show_lockmgr
+	.lc_ddb_show = db_show_lockmgr,
 #endif
+	.lc_lock = lock_lockmgr,
+	.lc_unlock = unlock_lockmgr,
 };
 
-
 /*
  * Locking primitives implementation.
  * Locks provide shared/exclusive sychronization.
  */
 
+void
+lock_lockmgr(struct lock_object *lock, int how)
+{
+
+	panic("lockmgr locks do not support sleep interlocking");
+}
+
+int
+unlock_lockmgr(struct lock_object *lock)
+{
+
+	panic("lockmgr locks do not support sleep interlocking");
+}
+
 #define	COUNT(td, x)	if ((td)) (td)->td_locks += (x)
 #define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \
 	LK_SHARE_NONZERO | LK_WAIT_NONZERO)