137 lines
3.5 KiB
C
137 lines
3.5 KiB
C
/* $NetBSD: kern_rwlock_obj.c,v 1.4 2018/02/05 04:25:04 ozaki-r Exp $ */
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/*-
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* Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Andrew Doran.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: kern_rwlock_obj.c,v 1.4 2018/02/05 04:25:04 ozaki-r Exp $");
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#include <sys/param.h>
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#include <sys/atomic.h>
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#include <sys/pool.h>
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#include <sys/rwlock.h>
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/* Mutex cache */
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#define RW_OBJ_MAGIC 0x85d3c85d
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struct krwobj {
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krwlock_t ro_lock;
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u_int ro_magic;
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u_int ro_refcnt;
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};
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static int rw_obj_ctor(void *, void *, int);
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static pool_cache_t rw_obj_cache __read_mostly;
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/*
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* rw_obj_init:
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*
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* Initialize the rw object store.
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*/
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void
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rw_obj_init(void)
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{
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rw_obj_cache = pool_cache_init(sizeof(struct krwobj),
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coherency_unit, 0, 0, "rwlock", NULL, IPL_NONE, rw_obj_ctor,
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NULL, NULL);
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}
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/*
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* rw_obj_ctor:
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*
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* Initialize a new lock for the cache.
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*/
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static int
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rw_obj_ctor(void *arg, void *obj, int flags)
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{
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struct krwobj * ro = obj;
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ro->ro_magic = RW_OBJ_MAGIC;
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return 0;
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}
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/*
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* rw_obj_alloc:
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*
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* Allocate a single lock object.
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*/
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krwlock_t *
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rw_obj_alloc(void)
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{
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struct krwobj *ro;
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extern void _rw_init(krwlock_t *, uintptr_t);
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ro = pool_cache_get(rw_obj_cache, PR_WAITOK);
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_rw_init(&ro->ro_lock, (uintptr_t)__builtin_return_address(0));
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ro->ro_refcnt = 1;
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return (krwlock_t *)ro;
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}
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/*
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* rw_obj_hold:
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*
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* Add a single reference to a lock object. A reference to the object
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* must already be held, and must be held across this call.
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*/
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void
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rw_obj_hold(krwlock_t *lock)
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{
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struct krwobj *ro = (struct krwobj *)lock;
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KASSERT(ro->ro_magic == RW_OBJ_MAGIC);
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KASSERT(ro->ro_refcnt > 0);
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atomic_inc_uint(&ro->ro_refcnt);
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}
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/*
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* rw_obj_free:
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*
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* Drop a reference from a lock object. If the last reference is being
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* dropped, free the object and return true. Otherwise, return false.
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*/
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bool
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rw_obj_free(krwlock_t *lock)
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{
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struct krwobj *ro = (struct krwobj *)lock;
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KASSERT(ro->ro_magic == RW_OBJ_MAGIC);
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KASSERT(ro->ro_refcnt > 0);
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if (atomic_dec_uint_nv(&ro->ro_refcnt) > 0) {
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return false;
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}
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rw_destroy(&ro->ro_lock);
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pool_cache_put(rw_obj_cache, ro);
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return true;
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}
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