NetBSD/sys/kern/kern_rwlock_obj.c

136 lines
3.4 KiB
C

/* $NetBSD: kern_rwlock_obj.c,v 1.3 2011/05/13 22:16:43 rmind Exp $ */
/*-
* Copyright (c) 2008, 2009 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.
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_rwlock_obj.c,v 1.3 2011/05/13 22:16:43 rmind Exp $");
#include <sys/param.h>
#include <sys/atomic.h>
#include <sys/pool.h>
#include <sys/rwlock.h>
/* Mutex cache */
#define RW_OBJ_MAGIC 0x85d3c85d
struct krwobj {
krwlock_t ro_lock;
u_int ro_magic;
u_int ro_refcnt;
};
static int rw_obj_ctor(void *, void *, int);
static pool_cache_t rw_obj_cache __read_mostly;
/*
* rw_obj_init:
*
* Initialize the rw object store.
*/
void
rw_obj_init(void)
{
rw_obj_cache = pool_cache_init(sizeof(struct krwobj),
coherency_unit, 0, 0, "rwlock", NULL, IPL_NONE, rw_obj_ctor,
NULL, NULL);
}
/*
* rw_obj_ctor:
*
* Initialize a new lock for the cache.
*/
static int
rw_obj_ctor(void *arg, void *obj, int flags)
{
struct krwobj * ro = obj;
ro->ro_magic = RW_OBJ_MAGIC;
return 0;
}
/*
* rw_obj_alloc:
*
* Allocate a single lock object.
*/
krwlock_t *
rw_obj_alloc(void)
{
struct krwobj *ro;
ro = pool_cache_get(rw_obj_cache, PR_WAITOK);
rw_init(&ro->ro_lock);
ro->ro_refcnt = 1;
return (krwlock_t *)ro;
}
/*
* 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(krwlock_t *lock)
{
struct krwobj *ro = (struct krwobj *)lock;
KASSERT(ro->ro_magic == RW_OBJ_MAGIC);
KASSERT(ro->ro_refcnt > 0);
atomic_inc_uint(&ro->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.
*/
bool
rw_obj_free(krwlock_t *lock)
{
struct krwobj *ro = (struct krwobj *)lock;
KASSERT(ro->ro_magic == RW_OBJ_MAGIC);
KASSERT(ro->ro_refcnt > 0);
if (atomic_dec_uint_nv(&ro->ro_refcnt) > 0) {
return false;
}
rw_destroy(&ro->ro_lock);
pool_cache_put(rw_obj_cache, ro);
return true;
}