New rw_obj_init() API providing reference-counted rwlock.

Original port from NetBSD by guenther@, required for upcoming amap & anon
locking.

ok kettenis@

3 files changed, 147 insertions, 3 deletions

diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
index 5825a1471cb..dd78c085828 100644
--- a/sys/kern/init_main.c
+++ b/sys/kern/init_main.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: init_main.c,v 1.304 2021/01/01 07:00:33 jsg Exp $	*/
+/*	$OpenBSD: init_main.c,v 1.305 2021/01/11 18:49:38 mpi Exp $	*/
 /*	$NetBSD: init_main.c,v 1.84.4.1 1996/06/02 09:08:06 mrg Exp $	*/
 
 /*
@@ -232,6 +232,7 @@ main(void *framep)
 	KERNEL_LOCK_INIT();
 	SCHED_LOCK_INIT();
 
+	rw_obj_init();
 	uvm_init();
 	disk_init();		/* must come before autoconfiguration */
 	tty_init();		/* initialise tty's */
diff --git a/sys/kern/kern_rwlock.c b/sys/kern/kern_rwlock.c
index 406df8f6007..c73b1b17fa1 100644
--- a/sys/kern/kern_rwlock.c
+++ b/sys/kern/kern_rwlock.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_rwlock.c,v 1.45 2020/03/02 17:07:49 visa Exp $	*/
+/*	$OpenBSD: kern_rwlock.c,v 1.46 2021/01/11 18:49:38 mpi Exp $	*/
 
 /*
  * Copyright (c) 2002, 2003 Artur Grabowski <art@openbsd.org>
@@ -19,6 +19,7 @@
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/pool.h>
 #include <sys/proc.h>
 #include <sys/rwlock.h>
 #include <sys/limits.h>
@@ -488,3 +489,123 @@ rrw_status(struct rrwlock *rrwl)
 {
 	return (rw_status(&rrwl->rrwl_lock));
 }
+
+/*-
+ * Copyright (c) 2008 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Andrew Doran.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define	RWLOCK_OBJ_MAGIC	0x5aa3c85d
+struct rwlock_obj {
+	struct rwlock	ro_lock;
+	u_int		ro_magic;
+	u_int		ro_refcnt;
+};
+
+
+struct pool rwlock_obj_pool;
+
+/*
+ * rw_obj_init:
+ *
+ *	Initialize the mutex object store.
+ */
+void
+rw_obj_init(void)
+{
+	pool_init(&rwlock_obj_pool, sizeof(struct rwlock_obj), 0, IPL_MPFLOOR,
+	    PR_WAITOK, "rwobjpl", NULL);
+}
+
+/*
+ * rw_obj_alloc:
+ *
+ *	Allocate a single lock object.
+ */
+void
+_rw_obj_alloc_flags(struct rwlock **lock, const char *name, int flags,
+    struct lock_type *type)
+{
+	struct rwlock_obj *mo;
+
+	mo = pool_get(&rwlock_obj_pool, PR_WAITOK);
+	mo->ro_magic = RWLOCK_OBJ_MAGIC;
+	_rw_init_flags(&mo->ro_lock, name, flags, type);
+	mo->ro_refcnt = 1;
+
+	*lock = &mo->ro_lock;
+}
+
+/*
+ * rw_obj_hold:
+ *
+ *	Add a single reference to a lock object.  A reference to the object
+ *	must already be held, and must be held across this call.
+ */
+
+void
+rw_obj_hold(struct rwlock *lock)
+{
+	struct rwlock_obj *mo = (struct rwlock_obj *)lock;
+
+	KASSERTMSG(mo->ro_magic == RWLOCK_OBJ_MAGIC,
+	    "%s: lock %p: mo->ro_magic (%#x) != RWLOCK_OBJ_MAGIC (%#x)",
+	     __func__, mo, mo->ro_magic, RWLOCK_OBJ_MAGIC);
+	KASSERTMSG(mo->ro_refcnt > 0,
+	    "%s: lock %p: mo->ro_refcnt (%#x) == 0",
+	     __func__, mo, mo->ro_refcnt);
+
+	atomic_inc_int(&mo->ro_refcnt);
+}
+
+/*
+ * rw_obj_free:
+ *
+ *	Drop a reference from a lock object.  If the last reference is being
+ *	dropped, free the object and return true.  Otherwise, return false.
+ */
+int
+rw_obj_free(struct rwlock *lock)
+{
+	struct rwlock_obj *mo = (struct rwlock_obj *)lock;
+
+	KASSERTMSG(mo->ro_magic == RWLOCK_OBJ_MAGIC,
+	    "%s: lock %p: mo->ro_magic (%#x) != RWLOCK_OBJ_MAGIC (%#x)",
+	     __func__, mo, mo->ro_magic, RWLOCK_OBJ_MAGIC);
+	KASSERTMSG(mo->ro_refcnt > 0,
+	    "%s: lock %p: mo->ro_refcnt (%#x) == 0",
+	     __func__, mo, mo->ro_refcnt);
+
+	if (atomic_dec_int_nv(&mo->ro_refcnt) > 0) {
+		return false;
+	}
+#if notyet
+	WITNESS_DESTROY(&mo->ro_lock);
+#endif
+	pool_put(&rwlock_obj_pool, mo);
+	return true;
+}
diff --git a/sys/sys/rwlock.h b/sys/sys/rwlock.h
index 9e6a7a26895..f5a2504f4e8 100644
--- a/sys/sys/rwlock.h
+++ b/sys/sys/rwlock.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rwlock.h,v 1.27 2020/12/15 10:23:01 mpi Exp $	*/
+/*	$OpenBSD: rwlock.h,v 1.28 2021/01/11 18:49:38 mpi Exp $	*/
 /*
  * Copyright (c) 2002 Artur Grabowski <art@openbsd.org>
  *
@@ -209,6 +209,28 @@ int	rrw_status(struct rrwlock *);
 #define rrw_init(rrwl, name)	_rrw_init_flags(rrwl, name, 0, NULL)
 #endif /* WITNESS */
 
+
+/*
+ * Allocated, reference-counted rwlocks
+ */
+
+#ifdef WITNESS
+#define rw_obj_alloc_flags(rwl, name, flags) do {			\
+	static struct lock_type __lock_type = { .lt_name = #rwl };	\
+	_rw_obj_alloc_flags(rwl, name, flags, &__lock_type);		\
+} while (0)
+#else
+#define rw_obj_alloc_flags(rwl, name, flags) \
+			_rw_obj_alloc_flags(rwl, name, flags, NULL)
+#endif
+#define rw_obj_alloc(rwl, name)		rw_obj_alloc_flags(rwl, name, 0)
+
+void	rw_obj_init(void);
+void	_rw_obj_alloc_flags(struct rwlock **, const char *, int,
+		struct lock_type *);
+void	rw_obj_hold(struct rwlock *);
+int	rw_obj_free(struct rwlock *);
+
 #endif /* _KERNEL */
 
 #endif /* _SYS_RWLOCK_H */