354 lines
8.8 KiB
C
354 lines
8.8 KiB
C
/* $NetBSD: pthread_lock.c,v 1.14 2005/03/17 17:23:21 jwise Exp $ */
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/*-
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* Copyright (c) 2001 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 Nathan J. Williams.
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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 NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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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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__RCSID("$NetBSD: pthread_lock.c,v 1.14 2005/03/17 17:23:21 jwise Exp $");
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#include <sys/types.h>
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#include <sys/lock.h>
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#include <sys/ras.h>
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#include <errno.h>
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#include <unistd.h>
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#include "pthread.h"
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#include "pthread_int.h"
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#ifdef PTHREAD_SPIN_DEBUG_PRINT
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#define SDPRINTF(x) DPRINTF(x)
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#else
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#define SDPRINTF(x)
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#endif
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/* How many times to try before checking whether we've been continued. */
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#define NSPINS 1000 /* no point in actually spinning until MP works */
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static int nspins = NSPINS;
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RAS_DECL(pthread__lock);
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static void
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pthread__ras_simple_lock_init(__cpu_simple_lock_t *alp)
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{
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*alp = __SIMPLELOCK_UNLOCKED;
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}
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static int
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pthread__ras_simple_lock_try(__cpu_simple_lock_t *alp)
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{
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__cpu_simple_lock_t old;
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RAS_START(pthread__lock);
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old = *alp;
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*alp = __SIMPLELOCK_LOCKED;
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RAS_END(pthread__lock);
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return (old == __SIMPLELOCK_UNLOCKED);
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}
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static void
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pthread__ras_simple_unlock(__cpu_simple_lock_t *alp)
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{
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*alp = __SIMPLELOCK_UNLOCKED;
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}
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static const struct pthread_lock_ops pthread__lock_ops_ras = {
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pthread__ras_simple_lock_init,
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pthread__ras_simple_lock_try,
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pthread__ras_simple_unlock,
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};
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static void
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pthread__atomic_simple_lock_init(__cpu_simple_lock_t *alp)
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{
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__cpu_simple_lock_init(alp);
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}
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static int
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pthread__atomic_simple_lock_try(__cpu_simple_lock_t *alp)
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{
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return (__cpu_simple_lock_try(alp));
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}
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static void
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pthread__atomic_simple_unlock(__cpu_simple_lock_t *alp)
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{
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__cpu_simple_unlock(alp);
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}
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static const struct pthread_lock_ops pthread__lock_ops_atomic = {
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pthread__atomic_simple_lock_init,
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pthread__atomic_simple_lock_try,
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pthread__atomic_simple_unlock,
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};
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/*
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* We default to pointing to the RAS primitives; we might need to use
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* locks early, but before main() starts. This is safe, since no other
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* threads will be active for the process, so atomicity will not be
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* required.
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*/
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const struct pthread_lock_ops *pthread__lock_ops = &pthread__lock_ops_ras;
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/*
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* Initialize the locking primitives. On uniprocessors, we always
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* use Restartable Atomic Sequences if they are available. Otherwise,
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* we fall back onto machine-dependent atomic lock primitives.
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*/
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void
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pthread__lockprim_init(int ncpu)
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{
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if (ncpu == 1 && rasctl(RAS_ADDR(pthread__lock),
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RAS_SIZE(pthread__lock), RAS_INSTALL) == 0) {
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pthread__lock_ops = &pthread__lock_ops_ras;
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return;
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}
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pthread__lock_ops = &pthread__lock_ops_atomic;
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}
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void
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pthread_lockinit(pthread_spin_t *lock)
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{
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pthread__simple_lock_init(lock);
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}
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void
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pthread_spinlock(pthread_t thread, pthread_spin_t *lock)
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{
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int count, ret;
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count = nspins;
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SDPRINTF(("(pthread_spinlock %p) incrementing spinlock %p (count %d)\n",
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thread, lock, thread->pt_spinlocks));
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#ifdef PTHREAD_SPIN_DEBUG
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pthread__assert(thread->pt_spinlocks >= 0);
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#endif
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++thread->pt_spinlocks;
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do {
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while (((ret = pthread__simple_lock_try(lock)) == 0) && --count)
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;
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if (ret == 1)
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break;
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SDPRINTF(("(pthread_spinlock %p) decrementing spinlock %p (count %d)\n",
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thread, lock, thread->pt_spinlocks));
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--thread->pt_spinlocks;
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/*
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* We may be preempted while spinning. If so, we will
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* be restarted here if thread->pt_spinlocks is
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* nonzero, which can happen if:
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* a) we just got the lock
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* b) we haven't yet decremented the lock count.
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* If we're at this point, (b) applies. Therefore,
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* check if we're being continued, and if so, bail.
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* (in case (a), we should let the code finish and
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* we will bail out in pthread_spinunlock()).
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*/
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if (thread->pt_next != NULL) {
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PTHREADD_ADD(PTHREADD_SPINPREEMPT);
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pthread__assert(thread->pt_blockgen == thread->pt_unblockgen);
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pthread__switch(thread, thread->pt_next);
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}
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/* try again */
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count = nspins;
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SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n",
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thread, thread->pt_spinlocks));
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++thread->pt_spinlocks;
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} while (/*CONSTCOND*/1);
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PTHREADD_ADD(PTHREADD_SPINLOCKS);
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/* Got it! We're out of here. */
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}
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int
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pthread_spintrylock(pthread_t thread, pthread_spin_t *lock)
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{
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int ret;
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SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n",
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thread, thread->pt_spinlocks));
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++thread->pt_spinlocks;
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ret = pthread__simple_lock_try(lock);
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if (ret == 0) {
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SDPRINTF(("(pthread_spintrylock %p) decrementing spinlock from %d\n",
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thread, thread->pt_spinlocks));
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--thread->pt_spinlocks;
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/* See above. */
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if (thread->pt_next != NULL) {
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PTHREADD_ADD(PTHREADD_SPINPREEMPT);
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pthread__assert(thread->pt_blockgen == thread->pt_unblockgen);
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pthread__switch(thread, thread->pt_next);
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}
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}
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return ret;
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}
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void
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pthread_spinunlock(pthread_t thread, pthread_spin_t *lock)
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{
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pthread__simple_unlock(lock);
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SDPRINTF(("(pthread_spinunlock %p) decrementing spinlock %p (count %d)\n",
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thread, lock, thread->pt_spinlocks));
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--thread->pt_spinlocks;
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#ifdef PTHREAD_SPIN_DEBUG
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pthread__assert(thread->pt_spinlocks >= 0);
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#endif
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PTHREADD_ADD(PTHREADD_SPINUNLOCKS);
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/*
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* If we were preempted while holding a spinlock, the
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* scheduler will notice this and continue us. To be good
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* citzens, we must now get out of here if that was our
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* last spinlock.
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* XXX when will we ever have more than one?
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*/
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if ((thread->pt_spinlocks == 0) && (thread->pt_next != NULL)) {
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PTHREADD_ADD(PTHREADD_SPINPREEMPT);
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/* pthread__assert(thread->pt_blockgen == thread->pt_unblockgen); */
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pthread__switch(thread, thread->pt_next);
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}
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}
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/*
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* Public (POSIX-specified) spinlocks.
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* These don't interact with the spin-preemption code, nor do they
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* perform any adaptive sleeping.
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*/
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int
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pthread_spin_init(pthread_spinlock_t *lock, int pshared)
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{
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#ifdef ERRORCHECK
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if ((lock == NULL) ||
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((pshared != PTHREAD_PROCESS_PRIVATE) &&
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(pshared != PTHREAD_PROCESS_SHARED)))
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return EINVAL;
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#endif
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lock->pts_magic = _PT_SPINLOCK_MAGIC;
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/*
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* We don't actually use the pshared flag for anything;
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* CPU simple locks have all the process-shared properties
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* that we want anyway.
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*/
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lock->pts_flags = pshared;
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pthread_lockinit(&lock->pts_spin);
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return 0;
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}
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int
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pthread_spin_destroy(pthread_spinlock_t *lock)
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{
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#ifdef ERRORCHECK
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if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC))
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return EINVAL;
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if (lock->pts_spin != __SIMPLELOCK_UNLOCKED)
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return EBUSY;
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#endif
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lock->pts_magic = _PT_SPINLOCK_DEAD;
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return 0;
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}
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int
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pthread_spin_lock(pthread_spinlock_t *lock)
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{
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#ifdef ERRORCHECK
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if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC))
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return EINVAL;
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#endif
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while (pthread__simple_lock_try(&lock->pts_spin) == 0)
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/* spin */ ;
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return 0;
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}
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int
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pthread_spin_trylock(pthread_spinlock_t *lock)
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{
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#ifdef ERRORCHECK
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if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC))
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return EINVAL;
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#endif
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if (pthread__simple_lock_try(&lock->pts_spin) == 0)
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return EBUSY;
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return 0;
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}
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int
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pthread_spin_unlock(pthread_spinlock_t *lock)
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{
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#ifdef ERRORCHECK
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if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC))
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return EINVAL;
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#endif
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pthread__simple_unlock(&lock->pts_spin);
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return 0;
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}
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