143 lines
3.7 KiB
C
143 lines
3.7 KiB
C
/* $NetBSD: kern_rwlock_obj.c,v 1.13 2023/10/02 21:03:55 ad Exp $ */
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/*-
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* Copyright (c) 2008, 2009, 2019, 2023 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 1.13 2023/10/02 21:03:55 ad Exp $");
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#include <sys/param.h>
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#include <sys/atomic.h>
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#include <sys/kmem.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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uint8_t mo_pad[COHERENCY_UNIT - sizeof(krwlock_t) -
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sizeof(u_int) * 2];
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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, waiting for memory if needed.
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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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ro = kmem_intr_alloc(sizeof(*ro), KM_SLEEP);
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KASSERT(ALIGNED_POINTER(ro, coherency_unit));
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_rw_init(&ro->ro_lock, (uintptr_t)__builtin_return_address(0));
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ro->ro_magic = RW_OBJ_MAGIC;
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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_tryalloc:
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*
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* Allocate a single lock object, but fail if no memory is available.
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*/
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krwlock_t *
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rw_obj_tryalloc(void)
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{
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struct krwobj *ro;
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ro = kmem_intr_alloc(sizeof(*ro), KM_NOSLEEP);
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KASSERT(ALIGNED_POINTER(ro, coherency_unit));
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if (__predict_true(ro != NULL)) {
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_rw_init(&ro->ro_lock, (uintptr_t)__builtin_return_address(0));
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ro->ro_magic = RW_OBJ_MAGIC;
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ro->ro_refcnt = 1;
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}
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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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membar_release();
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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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membar_acquire();
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rw_destroy(&ro->ro_lock);
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kmem_intr_free(ro, sizeof(*ro));
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return true;
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}
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/*
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* rw_obj_refcnt:
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*
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* Return the reference count for a lock object.
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*/
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u_int
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rw_obj_refcnt(krwlock_t *lock)
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{
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struct krwobj *ro = (struct krwobj *)lock;
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return ro->ro_refcnt;
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}
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