/* $NetBSD: pthread_lock.c,v 1.20 2007/03/24 18:52:00 ad Exp $ */ /*- * Copyright (c) 2001, 2006, 2007 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Nathan J. Williams and Andrew Doran. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the NetBSD * Foundation, Inc. and its contributors. * 4. Neither the name of The NetBSD Foundation nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ #include __RCSID("$NetBSD: pthread_lock.c,v 1.20 2007/03/24 18:52:00 ad Exp $"); #include #include #include #include #include #include #include "pthread.h" #include "pthread_int.h" #ifdef PTHREAD_SPIN_DEBUG_PRINT #define SDPRINTF(x) DPRINTF(x) #else #define SDPRINTF(x) #endif /* This does not belong here. */ #if defined(i386) || defined(__x86_64__) #define smt_pause() __asm __volatile("rep; nop" ::: "memory") #else #define smt_pause() /* nothing */ #endif extern int pthread__nspins; static int pthread__atomic; RAS_DECL(pthread__lock); void pthread__simple_lock_init(__cpu_simple_lock_t *alp) { if (pthread__atomic) { __cpu_simple_lock_init(alp); return; } *alp = __SIMPLELOCK_UNLOCKED; } int pthread__simple_lock_try(__cpu_simple_lock_t *alp) { __cpu_simple_lock_t old; if (pthread__atomic) return __cpu_simple_lock_try(alp); RAS_START(pthread__lock); old = *alp; *alp = __SIMPLELOCK_LOCKED; RAS_END(pthread__lock); return old == __SIMPLELOCK_UNLOCKED; } inline void pthread__simple_unlock(__cpu_simple_lock_t *alp) { if (pthread__atomic) { __cpu_simple_unlock(alp); return; } *alp = __SIMPLELOCK_UNLOCKED; } /* * Initialize the locking primitives. On uniprocessors, we always * use Restartable Atomic Sequences if they are available. Otherwise, * we fall back onto machine-dependent atomic lock primitives. */ void pthread__lockprim_init(int ncpu) { if (ncpu != 1) { pthread__atomic = 1; return; } if (rasctl(RAS_ADDR(pthread__lock), RAS_SIZE(pthread__lock), RAS_INSTALL) != 0) { pthread__atomic = 1; return; } } void pthread_lockinit(pthread_spin_t *lock) { pthread__simple_lock_init(lock); } void pthread_spinlock(pthread_t thread, pthread_spin_t *lock) { int count, ret; count = pthread__nspins; SDPRINTF(("(pthread_spinlock %p) spinlock %p (count %d)\n", thread, lock, thread->pt_spinlocks)); #ifdef PTHREAD_SPIN_DEBUG pthread__assert(thread->pt_spinlocks >= 0); #endif thread->pt_spinlocks++; if (__predict_true(pthread__simple_lock_try(lock))) { PTHREADD_ADD(PTHREADD_SPINLOCKS); return; } do { while ((ret = pthread__simple_lock_try(lock)) == 0 && --count) { smt_pause(); } if (ret == 1) break; SDPRINTF(("(pthread_spinlock %p) retrying spinlock %p " "(count %d)\n", thread, lock, thread->pt_spinlocks)); thread->pt_spinlocks--; /* XXXLWP far from ideal */ sched_yield(); count = pthread__nspins; thread->pt_spinlocks++; } while (/*CONSTCOND*/ 1); PTHREADD_ADD(PTHREADD_SPINLOCKS); } int pthread_spintrylock(pthread_t thread, pthread_spin_t *lock) { int ret; SDPRINTF(("(pthread_spintrylock %p) spinlock %p (count %d)\n", thread, lock, thread->pt_spinlocks)); thread->pt_spinlocks++; ret = pthread__simple_lock_try(lock); if (!ret) thread->pt_spinlocks--; return ret; } void pthread_spinunlock(pthread_t thread, pthread_spin_t *lock) { SDPRINTF(("(pthread_spinunlock %p) spinlock %p (count %d)\n", thread, lock, thread->pt_spinlocks)); pthread__simple_unlock(lock); thread->pt_spinlocks--; #ifdef PTHREAD_SPIN_DEBUG pthread__assert(thread->pt_spinlocks >= 0); #endif PTHREADD_ADD(PTHREADD_SPINUNLOCKS); } /* * Public (POSIX-specified) spinlocks. */ int pthread_spin_init(pthread_spinlock_t *lock, int pshared) { #ifdef ERRORCHECK if (lock == NULL || (pshared != PTHREAD_PROCESS_PRIVATE && pshared != PTHREAD_PROCESS_SHARED)) return EINVAL; #endif lock->pts_magic = _PT_SPINLOCK_MAGIC; /* * We don't actually use the pshared flag for anything; * CPU simple locks have all the process-shared properties * that we want anyway. */ lock->pts_flags = pshared; pthread_lockinit(&lock->pts_spin); return 0; } int pthread_spin_destroy(pthread_spinlock_t *lock) { #ifdef ERRORCHECK if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) return EINVAL; if (lock->pts_spin != __SIMPLELOCK_UNLOCKED) return EBUSY; #endif lock->pts_magic = _PT_SPINLOCK_DEAD; return 0; } int pthread_spin_lock(pthread_spinlock_t *lock) { #ifdef ERRORCHECK if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) return EINVAL; #endif while (pthread__simple_lock_try(&lock->pts_spin) == 0) { smt_pause(); } return 0; } int pthread_spin_trylock(pthread_spinlock_t *lock) { #ifdef ERRORCHECK if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) return EINVAL; #endif if (pthread__simple_lock_try(&lock->pts_spin) == 0) return EBUSY; return 0; } int pthread_spin_unlock(pthread_spinlock_t *lock) { #ifdef ERRORCHECK if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) return EINVAL; #endif pthread__simple_unlock(&lock->pts_spin); return 0; }