NetBSD/sys/kern/kern_mutex_obj.c

180 lines
4.7 KiB
C

/* $NetBSD: kern_mutex_obj.c,v 1.7 2020/01/01 21:34:39 ad Exp $ */
/*-
* Copyright (c) 2008, 2019 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_mutex_obj.c,v 1.7 2020/01/01 21:34:39 ad Exp $");
#include <sys/param.h>
#include <sys/atomic.h>
#include <sys/mutex.h>
#include <sys/pool.h>
/* Mutex cache */
#define MUTEX_OBJ_MAGIC 0x5aa3c85d
struct kmutexobj {
kmutex_t mo_lock;
u_int mo_magic;
u_int mo_refcnt;
};
static int mutex_obj_ctor(void *, void *, int);
static pool_cache_t mutex_obj_cache __read_mostly;
/*
* mutex_obj_init:
*
* Initialize the mutex object store.
*/
void
mutex_obj_init(void)
{
mutex_obj_cache = pool_cache_init(sizeof(struct kmutexobj),
coherency_unit, 0, 0, "mutex", NULL, IPL_NONE, mutex_obj_ctor,
NULL, NULL);
}
/*
* mutex_obj_ctor:
*
* Initialize a new lock for the cache.
*/
static int
mutex_obj_ctor(void *arg, void *obj, int flags)
{
struct kmutexobj * mo = obj;
mo->mo_magic = MUTEX_OBJ_MAGIC;
return 0;
}
/*
* mutex_obj_alloc:
*
* Allocate a single lock object, waiting for memory if needed.
*/
kmutex_t *
mutex_obj_alloc(kmutex_type_t type, int ipl)
{
struct kmutexobj *mo;
extern void _mutex_init(kmutex_t *, kmutex_type_t, int, uintptr_t);
mo = pool_cache_get(mutex_obj_cache, PR_WAITOK);
_mutex_init(&mo->mo_lock, type, ipl,
(uintptr_t)__builtin_return_address(0));
mo->mo_refcnt = 1;
return (kmutex_t *)mo;
}
/*
* mutex_obj_alloc:
*
* Allocate a single lock object, failing if no memory available.
*/
kmutex_t *
mutex_obj_tryalloc(kmutex_type_t type, int ipl)
{
struct kmutexobj *mo;
extern void _mutex_init(kmutex_t *, kmutex_type_t, int, uintptr_t);
mo = pool_cache_get(mutex_obj_cache, PR_NOWAIT);
if (__predict_true(mo != NULL)) {
_mutex_init(&mo->mo_lock, type, ipl,
(uintptr_t)__builtin_return_address(0));
mo->mo_refcnt = 1;
}
return (kmutex_t *)mo;
}
/*
* mutex_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
mutex_obj_hold(kmutex_t *lock)
{
struct kmutexobj *mo = (struct kmutexobj *)lock;
KASSERTMSG(mo->mo_magic == MUTEX_OBJ_MAGIC,
"%s: lock %p: mo->mo_magic (%#x) != MUTEX_OBJ_MAGIC (%#x)",
__func__, mo, mo->mo_magic, MUTEX_OBJ_MAGIC);
KASSERTMSG(mo->mo_refcnt > 0,
"%s: lock %p: mo->mo_refcnt (%#x) == 0",
__func__, mo, mo->mo_refcnt);
atomic_inc_uint(&mo->mo_refcnt);
}
/*
* mutex_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
mutex_obj_free(kmutex_t *lock)
{
struct kmutexobj *mo = (struct kmutexobj *)lock;
KASSERTMSG(mo->mo_magic == MUTEX_OBJ_MAGIC,
"%s: lock %p: mo->mo_magic (%#x) != MUTEX_OBJ_MAGIC (%#x)",
__func__, mo, mo->mo_magic, MUTEX_OBJ_MAGIC);
KASSERTMSG(mo->mo_refcnt > 0,
"%s: lock %p: mo->mo_refcnt (%#x) == 0",
__func__, mo, mo->mo_refcnt);
if (atomic_dec_uint_nv(&mo->mo_refcnt) > 0) {
return false;
}
mutex_destroy(&mo->mo_lock);
pool_cache_put(mutex_obj_cache, mo);
return true;
}
/*
* mutex_obj_refcnt:
*
* Return the reference count on a lock object.
*/
u_int
mutex_obj_refcnt(kmutex_t *lock)
{
struct kmutexobj *mo = (struct kmutexobj *)lock;
return mo->mo_refcnt;
}