Add _NEW flag to mtx(9), sx(9), rmlock(9) and rwlock(9).

A _NEW flag passed to _init_flags() to avoid check for double-init.

Differential Revision:	https://reviews.freebsd.org/D1208
Reviewed by:	jhb, wblock
MFC after:	1 Month

share/man/man9/mutex.9

@@ -28,7 +28,7 @@
 .\"	from BSDI $Id: mutex.4,v 1.1.2.3 1998/04/27 22:53:13 ewv Exp $
 .\" $FreeBSD$
 .\"
-.Dd November 16, 2011
+.Dd December 13, 2014
 .Dt MUTEX 9
 .Os
 .Sh NAME
@@ -177,13 +177,17 @@ It may contain either
 or
 .Dv MTX_SPIN
 but not both.
-See below for additional initialization options.
-It is not permissible to pass the same
-.Fa mutex
-to
+If the kernel has been compiled with
+.Cd "option INVARIANTS" ,
 .Fn mtx_init
-multiple times without intervening calls to
-.Fn mtx_destroy .
+will assert that the
+.Fa mutex
+has not been initialized multiple times without intervening calls to
+.Fn mtx_destroy
+unless the
+.Dv MTX_NEW
+option is specified.
+See below for additional initialization options.
 .Pp
 The
 .Fn mtx_lock
@@ -453,6 +457,8 @@ to ignore this lock.
 Witness should not log messages about duplicate locks being acquired.
 .It Dv MTX_NOPROFILE
 Do not profile this lock.
+.It Dv MTX_NEW
+Do not check for double-init.
 .El
 .Ss Lock and Unlock Flags
 The flags passed to the

share/man/man9/rmlock.9

@@ -26,7 +26,7 @@
 .\" $FreeBSD$
 .\"
 .\" Based on rwlock.9 man page
-.Dd June 25, 2013
+.Dd December 13, 2014
 .Dt RMLOCK 9
 .Os
 .Sh NAME
@@ -156,6 +156,15 @@ Allow threads to recursively acquire shared locks for
 .Fa rm .
 .It Dv RM_SLEEPABLE
 Create a sleepable read-mostly lock.
+.It Dv RM_NEW
+If the kernel has been compiled with
+.Cd "option INVARIANTS" ,
+.Fn rm_init_flags
+will assert that the
+.Fa rm
+has not been initialized multiple times without intervening calls to
+.Fn rm_destroy
+unless this option is specified.
 .El
 .It Fn rm_rlock "struct rmlock *rm" "struct rm_priotracker* tracker"
 Lock

share/man/man9/rwlock.9

@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd June 20, 2013
+.Dd December 13, 2014
 .Dt RWLOCK 9
 .Os
 .Sh NAME
@@ -154,6 +154,15 @@ Do not log any operations for this lock via
 .It Dv RW_RECURSE
 Allow threads to recursively acquire exclusive locks for
 .Fa rw .
+.It Dv RW_NEW
+If the kernel has been compiled with
+.Cd "option INVARIANTS" ,
+.Fn rw_init_flags
+will assert that the
+.Fa rw
+has not been initialized multiple times without intervening calls to
+.Fn rw_destroy
+unless this option is specified.
 .El
 .It Fn rw_rlock "struct rwlock *rw"
 Lock

share/man/man9/sx.9

@@ -26,7 +26,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd November 16, 2011
+.Dd December 13, 2014
 .Dt SX 9
 .Os
 .Sh NAME
@@ -144,6 +144,15 @@ Allow threads to recursively acquire exclusive locks for
 .It Dv SX_QUIET
 Do not log any operations for this lock via
 .Xr ktr 4 .
+.It Dv SX_NEW
+If the kernel has been compiled with
+.Cd "options INVARIANTS" ,
+.Fn sx_init
+will assert that the
+.Fa sx
+has not been initialized multiple times without intervening calls to
+.Fn sx_destroy
+unless this option is specified.
 .El
 .Pp
 Shared/exclusive locks are destroyed with

sys/kern/kern_mutex.c

@@ -881,7 +881,7 @@ _mtx_init(volatile uintptr_t *c, const char *name, const char *type, int opts)
 	m = mtxlock2mtx(c);
 
 	MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
-		MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE)) == 0);
+	    MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE | MTX_NEW)) == 0);
 	ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock,
 	    ("%s: mtx_lock not aligned for %s: %p", __func__, name,
 	    &m->mtx_lock));
@@ -907,6 +907,8 @@ _mtx_init(volatile uintptr_t *c, const char *name, const char *type, int opts)
 		flags |= LO_DUPOK;
 	if (opts & MTX_NOPROFILE)
 		flags |= LO_NOPROFILE;
+	if (opts & MTX_NEW)
+		flags |= LO_NEW;
 
 	/* Initialize mutex. */
 	lock_init(&m->lock_object, class, name, type, flags);

sys/kern/kern_rmlock.c

@@ -277,22 +277,28 @@ void
 rm_init_flags(struct rmlock *rm, const char *name, int opts)
 {
 	struct lock_class *lc;
-	int liflags;
+	int liflags, xflags;
 
 	liflags = 0;
 	if (!(opts & RM_NOWITNESS))
 		liflags |= LO_WITNESS;
 	if (opts & RM_RECURSE)
 		liflags |= LO_RECURSABLE;
+	if (opts & RM_NEW)
+		liflags |= LO_NEW;
 	rm->rm_writecpus = all_cpus;
 	LIST_INIT(&rm->rm_activeReaders);
 	if (opts & RM_SLEEPABLE) {
 		liflags |= LO_SLEEPABLE;
 		lc = &lock_class_rm_sleepable;
-		sx_init_flags(&rm->rm_lock_sx, "rmlock_sx", SX_NOWITNESS);
+		xflags = (opts & RM_NEW ? SX_NEW : 0);
+		sx_init_flags(&rm->rm_lock_sx, "rmlock_sx",
+		    xflags | SX_NOWITNESS);
 	} else {
 		lc = &lock_class_rm;
-		mtx_init(&rm->rm_lock_mtx, name, "rmlock_mtx", MTX_NOWITNESS);
+		xflags = (opts & RM_NEW ? MTX_NEW : 0);
+		mtx_init(&rm->rm_lock_mtx, name, "rmlock_mtx",
+		    xflags | MTX_NOWITNESS);
 	}
 	lock_init(&rm->lock_object, lc, name, NULL, liflags);
 }

sys/kern/kern_rwlock.c

@@ -187,7 +187,7 @@ _rw_init_flags(volatile uintptr_t *c, const char *name, int opts)
 	rw = rwlock2rw(c);
 
 	MPASS((opts & ~(RW_DUPOK | RW_NOPROFILE | RW_NOWITNESS | RW_QUIET |
-	    RW_RECURSE)) == 0);
+	    RW_RECURSE | RW_NEW)) == 0);
 	ASSERT_ATOMIC_LOAD_PTR(rw->rw_lock,
 	    ("%s: rw_lock not aligned for %s: %p", __func__, name,
 	    &rw->rw_lock));
@@ -203,6 +203,8 @@ _rw_init_flags(volatile uintptr_t *c, const char *name, int opts)
 		flags |= LO_RECURSABLE;
 	if (opts & RW_QUIET)
 		flags |= LO_QUIET;
+	if (opts & RW_NEW)
+		flags |= LO_NEW;
 
 	lock_init(&rw->lock_object, &lock_class_rw, name, NULL, flags);
 	rw->rw_lock = RW_UNLOCKED;

sys/kern/kern_sx.c

@@ -209,7 +209,7 @@ sx_init_flags(struct sx *sx, const char *description, int opts)
 	int flags;
 
 	MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK |
-	    SX_NOPROFILE | SX_NOADAPTIVE)) == 0);
+	    SX_NOPROFILE | SX_NOADAPTIVE | SX_NEW)) == 0);
 	ASSERT_ATOMIC_LOAD_PTR(sx->sx_lock,
 	    ("%s: sx_lock not aligned for %s: %p", __func__, description,
 	    &sx->sx_lock));
@@ -225,6 +225,8 @@ sx_init_flags(struct sx *sx, const char *description, int opts)
 		flags |= LO_RECURSABLE;
 	if (opts & SX_QUIET)
 		flags |= LO_QUIET;
+	if (opts & SX_NEW)
+		flags |= LO_NEW;
 
 	flags |= opts & SX_NOADAPTIVE;
 	lock_init(&sx->lock_object, &lock_class_sx, description, NULL, flags);

sys/kern/subr_lock.c

@@ -75,8 +75,8 @@ lock_init(struct lock_object *lock, struct lock_class *class, const char *name,
 	int i;
 
 	/* Check for double-init and zero object. */
-	KASSERT(!lock_initialized(lock), ("lock \"%s\" %p already initialized",
-	    name, lock));
+	KASSERT(flags & LO_NEW || !lock_initialized(lock),
+	    ("lock \"%s\" %p already initialized", name, lock));
 
 	/* Look up lock class to find its index. */
 	for (i = 0; i < LOCK_CLASS_MAX; i++)

sys/sys/lock.h

@@ -84,6 +84,7 @@ struct lock_class {
 #define	LO_IS_VNODE	0x00800000	/* Tell WITNESS about a VNODE lock */
 #define	LO_CLASSMASK	0x0f000000	/* Class index bitmask. */
 #define LO_NOPROFILE    0x10000000      /* Don't profile this lock */
+#define	LO_NEW		0x20000000	/* Don't check for double-init */
 
 /*
  * Lock classes are statically assigned an index into the gobal lock_classes

sys/sys/mutex.h

@@ -52,6 +52,7 @@
 #define MTX_RECURSE	0x00000004	/* Option: lock allowed to recurse */
 #define	MTX_NOWITNESS	0x00000008	/* Don't do any witness checking. */
 #define MTX_NOPROFILE   0x00000020	/* Don't profile this lock */
+#define	MTX_NEW		0x00000040	/* Don't check for double-init */
 
 /*
  * Option flags passed to certain lock/unlock routines, through the use

sys/sys/rmlock.h

@@ -45,6 +45,7 @@
 #define	RM_NOWITNESS	0x00000001
 #define	RM_RECURSE	0x00000002
 #define	RM_SLEEPABLE	0x00000004
+#define	RM_NEW		0x00000008
 
 void	rm_init(struct rmlock *rm, const char *name);
 void	rm_init_flags(struct rmlock *rm, const char *name, int opts);

sys/sys/rwlock.h

@@ -258,6 +258,7 @@ struct rw_args_flags {
 #define	RW_NOWITNESS	0x04
 #define	RW_QUIET	0x08
 #define	RW_RECURSE	0x10
+#define	RW_NEW		0x20
 
 /*
  * The INVARIANTS-enabled rw_assert() functionality.

sys/sys/sx.h

@@ -292,6 +292,7 @@ __sx_sunlock(struct sx *sx, const char *file, int line)
 #define	SX_QUIET		0x08
 #define	SX_NOADAPTIVE		0x10
 #define	SX_RECURSE		0x20
+#define	SX_NEW			0x40
 
 /*
  * Options passed to sx_*lock_hard().