Home | History | Annotate | Line # | Download | only in kern
kern_mutex_obj.c revision 1.6.4.1 
      1 /*	$NetBSD: kern_mutex_obj.c,v 1.6.4.1 2020/04/08 14:08:51 martin Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2008, 2019 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Andrew Doran.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 __KERNEL_RCSID(0, "$NetBSD: kern_mutex_obj.c,v 1.6.4.1 2020/04/08 14:08:51 martin Exp $");
     34 
     35 #include <sys/param.h>
     36 #include <sys/atomic.h>
     37 #include <sys/mutex.h>
     38 #include <sys/pool.h>
     39 
     40 /* Mutex cache */
     41 #define	MUTEX_OBJ_MAGIC	0x5aa3c85d
     42 struct kmutexobj {
     43 	kmutex_t	mo_lock;
     44 	u_int		mo_magic;
     45 	u_int		mo_refcnt;
     46 };
     47 
     48 static int	mutex_obj_ctor(void *, void *, int);
     49 
     50 static pool_cache_t	mutex_obj_cache		__read_mostly;
     51 
     52 /*
     53  * mutex_obj_init:
     54  *
     55  *	Initialize the mutex object store.
     56  */
     57 void
     58 mutex_obj_init(void)
     59 {
     60 
     61 	mutex_obj_cache = pool_cache_init(sizeof(struct kmutexobj),
     62 	    coherency_unit, 0, 0, "mutex", NULL, IPL_NONE, mutex_obj_ctor,
     63 	    NULL, NULL);
     64 }
     65 
     66 /*
     67  * mutex_obj_ctor:
     68  *
     69  *	Initialize a new lock for the cache.
     70  */
     71 static int
     72 mutex_obj_ctor(void *arg, void *obj, int flags)
     73 {
     74 	struct kmutexobj * mo = obj;
     75 
     76 	mo->mo_magic = MUTEX_OBJ_MAGIC;
     77 
     78 	return 0;
     79 }
     80 
     81 /*
     82  * mutex_obj_alloc:
     83  *
     84  *	Allocate a single lock object, waiting for memory if needed.
     85  */
     86 kmutex_t *
     87 mutex_obj_alloc(kmutex_type_t type, int ipl)
     88 {
     89 	struct kmutexobj *mo;
     90 	extern void _mutex_init(kmutex_t *, kmutex_type_t, int, uintptr_t);
     91 
     92 	mo = pool_cache_get(mutex_obj_cache, PR_WAITOK);
     93 	_mutex_init(&mo->mo_lock, type, ipl,
     94 	    (uintptr_t)__builtin_return_address(0));
     95 	mo->mo_refcnt = 1;
     96 
     97 	return (kmutex_t *)mo;
     98 }
     99 
    100 /*
    101  * mutex_obj_alloc:
    102  *
    103  *	Allocate a single lock object, failing if no memory available.
    104  */
    105 kmutex_t *
    106 mutex_obj_tryalloc(kmutex_type_t type, int ipl)
    107 {
    108 	struct kmutexobj *mo;
    109 	extern void _mutex_init(kmutex_t *, kmutex_type_t, int, uintptr_t);
    110 
    111 	mo = pool_cache_get(mutex_obj_cache, PR_NOWAIT);
    112 	if (__predict_true(mo != NULL)) {
    113 		_mutex_init(&mo->mo_lock, type, ipl,
    114 		    (uintptr_t)__builtin_return_address(0));
    115 		mo->mo_refcnt = 1;
    116 	}
    117 
    118 	return (kmutex_t *)mo;
    119 }
    120 
    121 /*
    122  * mutex_obj_hold:
    123  *
    124  *	Add a single reference to a lock object.  A reference to the object
    125  *	must already be held, and must be held across this call.
    126  */
    127 void
    128 mutex_obj_hold(kmutex_t *lock)
    129 {
    130 	struct kmutexobj *mo = (struct kmutexobj *)lock;
    131 
    132 	KASSERTMSG(mo->mo_magic == MUTEX_OBJ_MAGIC,
    133 	    "%s: lock %p: mo->mo_magic (%#x) != MUTEX_OBJ_MAGIC (%#x)",
    134 	     __func__, mo, mo->mo_magic, MUTEX_OBJ_MAGIC);
    135 	KASSERTMSG(mo->mo_refcnt > 0,
    136 	    "%s: lock %p: mo->mo_refcnt (%#x) == 0",
    137 	     __func__, mo, mo->mo_refcnt);
    138 
    139 	atomic_inc_uint(&mo->mo_refcnt);
    140 }
    141 
    142 /*
    143  * mutex_obj_free:
    144  *
    145  *	Drop a reference from a lock object.  If the last reference is being
    146  *	dropped, free the object and return true.  Otherwise, return false.
    147  */
    148 bool
    149 mutex_obj_free(kmutex_t *lock)
    150 {
    151 	struct kmutexobj *mo = (struct kmutexobj *)lock;
    152 
    153 	KASSERTMSG(mo->mo_magic == MUTEX_OBJ_MAGIC,
    154 	    "%s: lock %p: mo->mo_magic (%#x) != MUTEX_OBJ_MAGIC (%#x)",
    155 	     __func__, mo, mo->mo_magic, MUTEX_OBJ_MAGIC);
    156 	KASSERTMSG(mo->mo_refcnt > 0,
    157 	    "%s: lock %p: mo->mo_refcnt (%#x) == 0",
    158 	     __func__, mo, mo->mo_refcnt);
    159 
    160 	if (atomic_dec_uint_nv(&mo->mo_refcnt) > 0) {
    161 		return false;
    162 	}
    163 	mutex_destroy(&mo->mo_lock);
    164 	pool_cache_put(mutex_obj_cache, mo);
    165 	return true;
    166 }
    167 
    168 /*
    169  * mutex_obj_refcnt:
    170  *
    171  *	Return the reference count on a lock object.
    172  */
    173 u_int
    174 mutex_obj_refcnt(kmutex_t *lock)
    175 {
    176 	struct kmutexobj *mo = (struct kmutexobj *)lock;
    177 
    178 	return mo->mo_refcnt;
    179 }
    180