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Send this to the Attic so there's no mixups over which kern_lock.c is in
use in -current.
This commit is contained in:
Peter Wemm
parent
a4586acb0c
commit
92da7e012d
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=25074
@ -1,377 +0,0 @@
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/*
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* Copyright (c) 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* The Mach Operating System project at Carnegie-Mellon University.
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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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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: @(#)kern_lock.c 8.1 (Berkeley) 6/11/93
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*
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*
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* Copyright (c) 1987, 1990 Carnegie-Mellon University.
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* All rights reserved.
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*
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* Authors: Avadis Tevanian, Jr., Michael Wayne Young
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*
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* Permission to use, copy, modify and distribute this software and
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* its documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
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* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie the
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* rights to redistribute these changes.
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*
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* $Id$
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*/
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/*
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* Locking primitives implementation
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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/* XXX */
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#include <sys/proc.h>
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#include <vm/vm.h>
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#include <vm/vm_param.h>
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#include <vm/vm_prot.h>
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#include <vm/lock.h>
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/*
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* Routine: lock_init
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* Function:
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* Initialize a lock; required before use.
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* Note that clients declare the "struct lock"
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* variables and then initialize them, rather
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* than getting a new one from this module.
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*/
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void
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lock_init(l, can_sleep)
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lock_t l;
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boolean_t can_sleep;
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{
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l->want_write = 0;
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l->want_upgrade = 0;
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l->waiting = 0;
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l->can_sleep = can_sleep;
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l->read_count = 0;
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l->proc = NULL;
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l->recursion_depth = 0;
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}
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void
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lock_sleepable(l, can_sleep)
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lock_t l;
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boolean_t can_sleep;
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{
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l->can_sleep = can_sleep;
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}
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/*
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* Sleep locks. These use the same data structure and algorithm
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* as the spin locks, but the process sleeps while it is waiting
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* for the lock. These work on uniprocessor systems.
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*/
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void
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lock_write(l)
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register lock_t l;
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{
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if (l->proc == curproc) {
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/*
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* Recursive lock.
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*/
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l->recursion_depth++;
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return;
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}
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/*
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* Try to acquire the want_write bit.
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*/
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while (l->want_write) {
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if (l->can_sleep && l->want_write) {
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l->waiting = TRUE;
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tsleep(l, PVM, "lckwt1", 0);
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}
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}
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l->want_write = TRUE;
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/* Wait for readers (and upgrades) to finish */
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while ((l->read_count != 0) || l->want_upgrade) {
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if (l->can_sleep && (l->read_count != 0 || l->want_upgrade)) {
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l->waiting = TRUE;
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tsleep(l, PVM, "lckwt2", 0);
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}
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}
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}
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void
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lock_done(l)
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register lock_t l;
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{
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if (l->read_count != 0)
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l->read_count--;
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else if (l->recursion_depth != 0)
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l->recursion_depth--;
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else if (l->want_upgrade)
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l->want_upgrade = FALSE;
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else
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l->want_write = FALSE;
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if (l->waiting) {
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l->waiting = FALSE;
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wakeup(l);
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}
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}
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void
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lock_read(l)
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register lock_t l;
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{
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if (l->proc == curproc) {
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/*
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* Recursive lock.
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*/
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l->read_count++;
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return;
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}
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while (l->want_write || l->want_upgrade) {
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if (l->can_sleep && (l->want_write || l->want_upgrade)) {
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l->waiting = TRUE;
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tsleep(l, PVM, "lockrd", 0);
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}
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}
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l->read_count++;
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}
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/*
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* Routine: lock_read_to_write
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* Function:
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* Improves a read-only lock to one with
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* write permission. If another reader has
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* already requested an upgrade to a write lock,
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* no lock is held upon return.
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*
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* Returns TRUE if the upgrade *failed*.
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*/
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boolean_t
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lock_read_to_write(l)
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register lock_t l;
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{
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l->read_count--;
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if (l->proc == curproc) {
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/*
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* Recursive lock.
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*/
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l->recursion_depth++;
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return (FALSE);
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}
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if (l->want_upgrade) {
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/*
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* Someone else has requested upgrade. Since we've released a
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* read lock, wake him up.
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*/
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if (l->waiting) {
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l->waiting = FALSE;
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wakeup(l);
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}
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return (TRUE);
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}
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l->want_upgrade = TRUE;
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while (l->read_count != 0) {
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if (l->can_sleep && l->read_count != 0) {
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l->waiting = TRUE;
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tsleep(l, PVM, "lckrw", 0);
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}
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}
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return (FALSE);
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}
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void
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lock_write_to_read(l)
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register lock_t l;
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{
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l->read_count++;
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if (l->recursion_depth != 0)
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l->recursion_depth--;
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else if (l->want_upgrade)
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l->want_upgrade = FALSE;
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else
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l->want_write = FALSE;
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if (l->waiting) {
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l->waiting = FALSE;
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wakeup(l);
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}
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}
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/*
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* Routine: lock_try_write
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* Function:
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* Tries to get a write lock.
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*
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* Returns FALSE if the lock is not held on return.
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*/
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boolean_t
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lock_try_write(l)
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register lock_t l;
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{
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if (l->proc == curproc) {
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/*
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* Recursive lock
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*/
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l->recursion_depth++;
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return (TRUE);
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}
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if (l->want_write || l->want_upgrade || l->read_count) {
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/*
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* Can't get lock.
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*/
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return (FALSE);
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}
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/*
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* Have lock.
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*/
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l->want_write = TRUE;
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return (TRUE);
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}
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/*
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* Routine: lock_try_read
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* Function:
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* Tries to get a read lock.
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*
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* Returns FALSE if the lock is not held on return.
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*/
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boolean_t
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lock_try_read(l)
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register lock_t l;
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{
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if (l->proc == curproc) {
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/*
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* Recursive lock
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*/
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l->read_count++;
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return (TRUE);
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}
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if (l->want_write || l->want_upgrade) {
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return (FALSE);
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}
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l->read_count++;
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return (TRUE);
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}
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/*
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* Routine: lock_try_read_to_write
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* Function:
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* Improves a read-only lock to one with
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* write permission. If another reader has
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* already requested an upgrade to a write lock,
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* the read lock is still held upon return.
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*
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* Returns FALSE if the upgrade *failed*.
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*/
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boolean_t
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lock_try_read_to_write(l)
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register lock_t l;
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{
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if (l->proc == curproc) {
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/*
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* Recursive lock
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*/
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l->read_count--;
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l->recursion_depth++;
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return (TRUE);
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}
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if (l->want_upgrade) {
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return (FALSE);
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}
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l->want_upgrade = TRUE;
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l->read_count--;
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while (l->read_count != 0) {
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l->waiting = TRUE;
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tsleep(l, PVM, "lcktrw", 0);
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}
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return (TRUE);
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}
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/*
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* Allow a process that has a lock for write to acquire it
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* recursively (for read, write, or update).
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*/
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void
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lock_set_recursive(l)
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lock_t l;
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{
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if (!l->want_write) {
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panic("lock_set_recursive: don't have write lock");
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}
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l->proc = curproc;
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}
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/*
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* Prevent a lock from being re-acquired.
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*/
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void
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lock_clear_recursive(l)
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lock_t l;
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{
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if (l->proc != curproc) {
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panic("lock_clear_recursive: wrong proc");
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}
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if (l->recursion_depth == 0)
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l->proc = NULL;
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}
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