273 lines
6.5 KiB
C
273 lines
6.5 KiB
C
/* $NetBSD: pthread_lock.c,v 1.27 2007/09/10 11:34:05 skrll Exp $ */
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/*-
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* Copyright (c) 2001, 2006, 2007 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 and 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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* 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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/*
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* libpthread internal spinlock routines.
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*/
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#include <sys/cdefs.h>
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__RCSID("$NetBSD: pthread_lock.c,v 1.27 2007/09/10 11:34:05 skrll 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 <stdio.h>
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#include <stdlib.h>
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#include "pthread.h"
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#include "pthread_int.h"
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/* How many times to try acquiring spin locks on MP systems. */
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#define PTHREAD__NSPINS 1024
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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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static void pthread_spinlock_slow(pthread_spin_t *);
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static int pthread__atomic;
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RAS_DECL(pthread__lock);
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RAS_DECL(pthread__lock2);
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int
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pthread__simple_locked_p(__cpu_simple_lock_t *alp)
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{
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return __SIMPLELOCK_LOCKED_P(alp);
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}
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void
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pthread__simple_lock_init(__cpu_simple_lock_t *alp)
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{
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if (pthread__atomic) {
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__cpu_simple_lock_init(alp);
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return;
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}
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__cpu_simple_lock_clear(alp);
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}
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int
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pthread__simple_lock_try(__cpu_simple_lock_t *alp)
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{
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int unlocked;
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if (pthread__atomic)
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return __cpu_simple_lock_try(alp);
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RAS_START(pthread__lock);
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unlocked = __SIMPLELOCK_UNLOCKED_P(alp);
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__cpu_simple_lock_set(alp);
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RAS_END(pthread__lock);
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return unlocked;
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}
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inline void
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pthread__simple_unlock(__cpu_simple_lock_t *alp)
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{
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#ifdef PTHREAD__CHEAP_UNLOCK
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__cpu_simple_unlock(alp);
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#else
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if (pthread__atomic) {
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__cpu_simple_unlock(alp);
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return;
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}
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__cpu_simple_lock_clear(alp);
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#endif
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}
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void
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pthread_spinlock(pthread_spin_t *lock)
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{
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#ifdef PTHREAD_SPIN_DEBUG
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pthread_t thread = pthread__self();
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SDPRINTF(("(pthread_spinlock %p) spinlock %p (count %d)\n",
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thread, lock, thread->pt_spinlocks));
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pthread__assert(thread->pt_spinlocks >= 0);
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thread->pt_spinlocks++;
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PTHREADD_ADD(PTHREADD_SPINLOCKS);
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#endif
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if (pthread__atomic) {
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if (__predict_true(__cpu_simple_lock_try(lock)))
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return;
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} else {
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int unlocked;
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RAS_START(pthread__lock2);
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unlocked = __SIMPLELOCK_UNLOCKED_P(lock);
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__cpu_simple_lock_set(lock);
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RAS_END(pthread__lock2);
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if (__predict_true(unlocked))
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return;
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}
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pthread_spinlock_slow(lock);
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}
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/*
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* Prevent this routine from being inlined. The common case is no
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* contention and it's better to not burden the instruction decoder.
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*/
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#if __GNUC_PREREQ__(3, 0)
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__attribute ((noinline))
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#endif
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static void
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pthread_spinlock_slow(pthread_spin_t *lock)
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{
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int count;
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#ifdef PTHREAD_SPIN_DEBUG
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pthread_t thread = pthread__self();
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#endif
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do {
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count = pthread__nspins;
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while (pthread__simple_locked_p(lock) && --count > 0)
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pthread__smt_pause();
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if (count > 0) {
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if (pthread__simple_lock_try(lock))
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break;
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continue;
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}
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#ifdef PTHREAD_SPIN_DEBUG
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SDPRINTF(("(pthread_spinlock %p) retrying spinlock %p "
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"(count %d)\n", thread, lock,
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thread->pt_spinlocks));
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thread->pt_spinlocks--;
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/* XXXLWP far from ideal */
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sched_yield();
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thread->pt_spinlocks++;
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#else
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/* XXXLWP far from ideal */
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sched_yield();
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#endif
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} while (/*CONSTCOND*/ 1);
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}
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int
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pthread_spintrylock(pthread_spin_t *lock)
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{
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#ifdef PTHREAD_SPIN_DEBUG
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pthread_t thread = pthread__self();
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int ret;
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SDPRINTF(("(pthread_spintrylock %p) 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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ret = pthread__simple_lock_try(lock);
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if (!ret)
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thread->pt_spinlocks--;
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return ret;
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#else
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return pthread__simple_lock_try(lock);
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#endif
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}
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void
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pthread_spinunlock(pthread_spin_t *lock)
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{
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#ifdef PTHREAD_SPIN_DEBUG
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pthread_t thread = pthread__self();
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SDPRINTF(("(pthread_spinunlock %p) spinlock %p (count %d)\n",
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thread, lock, thread->pt_spinlocks));
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pthread__simple_unlock(lock);
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thread->pt_spinlocks--;
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pthread__assert(thread->pt_spinlocks >= 0);
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PTHREADD_ADD(PTHREADD_SPINUNLOCKS);
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#else
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pthread__simple_unlock(lock);
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#endif
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}
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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(void)
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{
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char *p;
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if ((p = getenv("PTHREAD_NSPINS")) != NULL)
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pthread__nspins = atoi(p);
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else if (pthread__concurrency != 1)
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pthread__nspins = PTHREAD__NSPINS;
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else
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pthread__nspins = 1;
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if (pthread__concurrency != 1) {
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pthread__atomic = 1;
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return;
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}
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if (rasctl(RAS_ADDR(pthread__lock), RAS_SIZE(pthread__lock),
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RAS_INSTALL) != 0) {
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pthread__atomic = 1;
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return;
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}
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if (rasctl(RAS_ADDR(pthread__lock2), RAS_SIZE(pthread__lock2),
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RAS_INSTALL) != 0) {
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pthread__atomic = 1;
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return;
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}
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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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