363 lines
9.6 KiB
C
363 lines
9.6 KiB
C
/*-
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* Copyright (c) 2001, 2003 Daniel Eischen <deischen@freebsd.org>.
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* All rights reserved.
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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 AUTHORS 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 AUTHOR 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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* $FreeBSD$
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*/
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#include <sys/types.h>
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#include <machine/atomic.h>
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#include <assert.h>
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#include <stdlib.h>
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#include "atomic_ops.h"
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#include "lock.h"
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#ifdef _LOCK_DEBUG
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#define LCK_ASSERT(e) assert(e)
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#else
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#define LCK_ASSERT(e)
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#endif
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#define MAX_SPINS 500
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void
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_lock_destroy(struct lock *lck)
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{
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if ((lck != NULL) && (lck->l_head != NULL)) {
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free(lck->l_head);
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lck->l_head = NULL;
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lck->l_tail = NULL;
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}
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}
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int
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_lock_init(struct lock *lck, enum lock_type ltype,
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lock_handler_t *waitfunc, lock_handler_t *wakeupfunc,
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void *(calloc_cb)(size_t, size_t))
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{
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if (lck == NULL)
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return (-1);
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else if ((lck->l_head = calloc_cb(1, sizeof(struct lockreq))) == NULL)
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return (-1);
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else {
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lck->l_type = ltype;
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lck->l_wait = waitfunc;
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lck->l_wakeup = wakeupfunc;
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lck->l_head->lr_locked = 0;
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lck->l_head->lr_watcher = NULL;
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lck->l_head->lr_owner = NULL;
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lck->l_head->lr_active = 1;
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lck->l_tail = lck->l_head;
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}
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return (0);
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}
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int
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_lock_reinit(struct lock *lck, enum lock_type ltype,
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lock_handler_t *waitfunc, lock_handler_t *wakeupfunc)
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{
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if (lck == NULL)
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return (-1);
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else if (lck->l_head == NULL)
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return (_lock_init(lck, ltype, waitfunc, wakeupfunc, calloc));
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else {
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lck->l_head->lr_locked = 0;
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lck->l_head->lr_watcher = NULL;
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lck->l_head->lr_owner = NULL;
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lck->l_head->lr_active = 1;
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lck->l_tail = lck->l_head;
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}
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return (0);
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}
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int
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_lockuser_init(struct lockuser *lu, void *priv)
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{
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if (lu == NULL)
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return (-1);
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else if ((lu->lu_myreq == NULL) &&
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((lu->lu_myreq = malloc(sizeof(struct lockreq))) == NULL))
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return (-1);
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else {
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lu->lu_myreq->lr_locked = 1;
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lu->lu_myreq->lr_watcher = NULL;
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lu->lu_myreq->lr_owner = lu;
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lu->lu_myreq->lr_active = 0;
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lu->lu_watchreq = NULL;
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lu->lu_priority = 0;
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lu->lu_private = priv;
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lu->lu_private2 = NULL;
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}
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return (0);
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}
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int
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_lockuser_reinit(struct lockuser *lu, void *priv)
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{
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if (lu == NULL)
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return (-1);
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if (lu->lu_watchreq != NULL) {
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/*
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* In this case the lock is active. All lockusers
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* keep their watch request and drop their own
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* (lu_myreq) request. Their own request is either
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* some other lockuser's watch request or is the
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* head of the lock.
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*/
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lu->lu_myreq = lu->lu_watchreq;
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lu->lu_watchreq = NULL;
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}
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if (lu->lu_myreq == NULL)
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/*
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* Oops, something isn't quite right. Try to
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* allocate one.
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*/
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return (_lockuser_init(lu, priv));
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else {
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lu->lu_myreq->lr_locked = 1;
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lu->lu_myreq->lr_watcher = NULL;
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lu->lu_myreq->lr_owner = lu;
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lu->lu_myreq->lr_active = 0;
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lu->lu_watchreq = NULL;
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lu->lu_priority = 0;
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lu->lu_private = priv;
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lu->lu_private2 = NULL;
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}
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return (0);
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}
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void
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_lockuser_destroy(struct lockuser *lu)
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{
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if ((lu != NULL) && (lu->lu_myreq != NULL))
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free(lu->lu_myreq);
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}
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/*
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* Acquire a lock waiting (spin or sleep) for it to become available.
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*/
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void
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_lock_acquire(struct lock *lck, struct lockuser *lu, int prio)
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{
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int i;
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int lval;
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/**
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* XXX - We probably want to remove these checks to optimize
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* performance. It is also a bug if any one of the
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* checks fail, so it's probably better to just let it
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* SEGV and fix it.
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*/
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#if 0
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if (lck == NULL || lu == NULL || lck->l_head == NULL)
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return;
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#endif
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if ((lck->l_type & LCK_PRIORITY) != 0) {
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LCK_ASSERT(lu->lu_myreq->lr_locked == 1);
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LCK_ASSERT(lu->lu_myreq->lr_watcher == NULL);
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LCK_ASSERT(lu->lu_myreq->lr_owner == lu);
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LCK_ASSERT(lu->lu_watchreq == NULL);
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lu->lu_priority = prio;
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}
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/*
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* Atomically swap the head of the lock request with
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* this request.
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*/
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atomic_swap_ptr((void *)&lck->l_head, lu->lu_myreq,
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(void *)&lu->lu_watchreq);
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if (lu->lu_watchreq->lr_locked != 0) {
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atomic_store_rel_ptr
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((volatile uintptr_t *)(void *)&lu->lu_watchreq->lr_watcher,
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(uintptr_t)lu);
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if ((lck->l_wait == NULL) ||
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((lck->l_type & LCK_ADAPTIVE) == 0)) {
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while (lu->lu_watchreq->lr_locked != 0)
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; /* spin, then yield? */
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} else {
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/*
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* Spin for a bit before invoking the wait function.
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*
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* We should be a little smarter here. If we're
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* running on a single processor, then the lock
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* owner got preempted and spinning will accomplish
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* nothing but waste time. If we're running on
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* multiple processors, the owner could be running
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* on another CPU and we might acquire the lock if
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* we spin for a bit.
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*
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* The other thing to keep in mind is that threads
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* acquiring these locks are considered to be in
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* critical regions; they will not be preempted by
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* the _UTS_ until they release the lock. It is
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* therefore safe to assume that if a lock can't
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* be acquired, it is currently held by a thread
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* running in another KSE.
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*/
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for (i = 0; i < MAX_SPINS; i++) {
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if (lu->lu_watchreq->lr_locked == 0)
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return;
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if (lu->lu_watchreq->lr_active == 0)
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break;
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}
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atomic_swap_int(&lu->lu_watchreq->lr_locked,
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2, &lval);
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if (lval == 0)
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lu->lu_watchreq->lr_locked = 0;
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else
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lck->l_wait(lck, lu);
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}
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}
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lu->lu_myreq->lr_active = 1;
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}
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/*
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* Release a lock.
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*/
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void
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_lock_release(struct lock *lck, struct lockuser *lu)
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{
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struct lockuser *lu_tmp, *lu_h;
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struct lockreq *myreq;
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int prio_h;
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int lval;
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/**
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* XXX - We probably want to remove these checks to optimize
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* performance. It is also a bug if any one of the
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* checks fail, so it's probably better to just let it
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* SEGV and fix it.
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*/
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#if 0
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if ((lck == NULL) || (lu == NULL))
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return;
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#endif
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if ((lck->l_type & LCK_PRIORITY) != 0) {
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prio_h = 0;
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lu_h = NULL;
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/* Update tail if our request is last. */
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if (lu->lu_watchreq->lr_owner == NULL) {
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atomic_store_rel_ptr((volatile uintptr_t *)
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(void *)&lck->l_tail,
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(uintptr_t)lu->lu_myreq);
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atomic_store_rel_ptr((volatile uintptr_t *)
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(void *)&lu->lu_myreq->lr_owner,
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(uintptr_t)NULL);
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} else {
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/* Remove ourselves from the list. */
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atomic_store_rel_ptr((volatile uintptr_t *)
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(void *)&lu->lu_myreq->lr_owner,
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(uintptr_t)lu->lu_watchreq->lr_owner);
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atomic_store_rel_ptr((volatile uintptr_t *)
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(void *)&lu->lu_watchreq->lr_owner->lu_myreq,
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(uintptr_t)lu->lu_myreq);
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}
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/*
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* The watch request now becomes our own because we've
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* traded away our previous request. Save our previous
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* request so that we can grant the lock.
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*/
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myreq = lu->lu_myreq;
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lu->lu_myreq = lu->lu_watchreq;
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lu->lu_watchreq = NULL;
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lu->lu_myreq->lr_locked = 1;
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lu->lu_myreq->lr_owner = lu;
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lu->lu_myreq->lr_watcher = NULL;
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/*
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* Traverse the list of lock requests in reverse order
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* looking for the user with the highest priority.
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*/
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for (lu_tmp = lck->l_tail->lr_watcher; lu_tmp != NULL;
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lu_tmp = lu_tmp->lu_myreq->lr_watcher) {
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if (lu_tmp->lu_priority > prio_h) {
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lu_h = lu_tmp;
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prio_h = lu_tmp->lu_priority;
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}
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}
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if (lu_h != NULL) {
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/* Give the lock to the highest priority user. */
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if (lck->l_wakeup != NULL) {
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atomic_swap_int(
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&lu_h->lu_watchreq->lr_locked,
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0, &lval);
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if (lval == 2)
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/* Notify the sleeper */
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lck->l_wakeup(lck,
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lu_h->lu_myreq->lr_watcher);
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}
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else
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atomic_store_rel_int(
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&lu_h->lu_watchreq->lr_locked, 0);
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} else {
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if (lck->l_wakeup != NULL) {
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atomic_swap_int(&myreq->lr_locked,
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0, &lval);
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if (lval == 2)
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/* Notify the sleeper */
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lck->l_wakeup(lck, myreq->lr_watcher);
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}
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else
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/* Give the lock to the previous request. */
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atomic_store_rel_int(&myreq->lr_locked, 0);
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}
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} else {
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/*
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* The watch request now becomes our own because we've
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* traded away our previous request. Save our previous
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* request so that we can grant the lock.
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*/
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myreq = lu->lu_myreq;
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lu->lu_myreq = lu->lu_watchreq;
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lu->lu_watchreq = NULL;
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lu->lu_myreq->lr_locked = 1;
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if (lck->l_wakeup) {
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atomic_swap_int(&myreq->lr_locked, 0, &lval);
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if (lval == 2)
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/* Notify the sleeper */
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lck->l_wakeup(lck, myreq->lr_watcher);
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}
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else
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/* Give the lock to the previous request. */
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atomic_store_rel_int(&myreq->lr_locked, 0);
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}
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lu->lu_myreq->lr_active = 0;
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}
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void
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_lock_grant(struct lock *lck __unused /* unused */, struct lockuser *lu)
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{
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atomic_store_rel_int(&lu->lu_watchreq->lr_locked, 3);
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}
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void
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_lockuser_setactive(struct lockuser *lu, int active)
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{
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lu->lu_myreq->lr_active = active;
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}
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