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/* $NetBSD: pthread_lock.c,v 1.7 2003/05/16 23:37:47 scw Exp $ */
/*-
* Copyright (c) 2001 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Nathan J. Williams.
*
* 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 <sys/cdefs.h>
__RCSID("$NetBSD: pthread_lock.c,v 1.7 2003/05/16 23:37:47 scw Exp $");
#include <sys/param.h>
#include <sys/ras.h>
#include <sys/sysctl.h>
#include <errno.h>
#include <unistd.h>
#include "pthread.h"
#include "pthread_int.h"
#ifdef PTHREAD_SPIN_DEBUG_PRINT
#define SDPRINTF(x) DPRINTF(x)
#else
#define SDPRINTF(x)
#endif
/* How many times to try before checking whether we've been continued. */
#define NSPINS 1 /* no point in actually spinning until MP works */
static int nspins = NSPINS;
extern void pthread__lock_ras_start(void), pthread__lock_ras_end(void);
static void
pthread__ras_simple_lock_init(__cpu_simple_lock_t *alp)
{
*alp = __SIMPLELOCK_UNLOCKED;
}
static int
pthread__ras_simple_lock_try(__cpu_simple_lock_t *alp)
{
__cpu_simple_lock_t old;
/* This is the atomic sequence. */
__asm __volatile(".globl pthread__lock_ras_start; pthread__lock_ras_start:");
old = *alp;
*alp = __SIMPLELOCK_LOCKED;
__asm __volatile(".globl pthread__lock_ras_end; pthread__lock_ras_end:");
return (old == __SIMPLELOCK_UNLOCKED);
}
static void
pthread__ras_simple_unlock(__cpu_simple_lock_t *alp)
{
*alp = __SIMPLELOCK_UNLOCKED;
}
static const struct pthread_lock_ops pthread__lock_ops_ras = {
pthread__ras_simple_lock_init,
pthread__ras_simple_lock_try,
pthread__ras_simple_unlock,
};
static void
pthread__atomic_simple_lock_init(__cpu_simple_lock_t *alp)
{
__cpu_simple_lock_init(alp);
}
static int
pthread__atomic_simple_lock_try(__cpu_simple_lock_t *alp)
{
return (__cpu_simple_lock_try(alp));
}
static void
pthread__atomic_simple_unlock(__cpu_simple_lock_t *alp)
{
__cpu_simple_unlock(alp);
}
static const struct pthread_lock_ops pthread__lock_ops_atomic = {
pthread__atomic_simple_lock_init,
pthread__atomic_simple_lock_try,
pthread__atomic_simple_unlock,
};
/*
* We default to pointing to the RAS primitives; we might need to use
* locks early, but before main() starts. This is safe, since no other
* threads will be active for the process, so atomicity will not be
* required.
*/
const struct pthread_lock_ops *pthread__lock_ops = &pthread__lock_ops_ras;
/*
* 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(void)
{
int mib[2];
size_t len;
int ncpu;
mib[0] = CTL_HW;
mib[1] = HW_NCPU;
len = sizeof(ncpu);
sysctl(mib, 2, &ncpu, &len, NULL, 0);
if (ncpu == 1 && rasctl((void *)pthread__lock_ras_start,
(size_t)((uintptr_t)pthread__lock_ras_end -
(uintptr_t)pthread__lock_ras_start),
RAS_INSTALL) == 0) {
pthread__lock_ops = &pthread__lock_ops_ras;
return;
}
pthread__lock_ops = &pthread__lock_ops_atomic;
}
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 = nspins;
SDPRINTF(("(pthread_spinlock %p) incrementing spinlock %p (count %d)\n",
thread, lock, thread->pt_spinlocks));
#ifdef PTHREAD_SPIN_DEBUG
pthread__assert(thread->pt_spinlocks >= 0);
#endif
++thread->pt_spinlocks;
do {
while (((ret = pthread__simple_lock_try(lock)) == 0) && --count)
;
if (ret == 1)
break;
SDPRINTF(("(pthread_spinlock %p) decrementing spinlock %p (count %d)\n",
thread, lock, thread->pt_spinlocks));
--thread->pt_spinlocks;
/*
* We may be preempted while spinning. If so, we will
* be restarted here if thread->pt_spinlocks is
* nonzero, which can happen if:
* a) we just got the lock
* b) we haven't yet decremented the lock count.
* If we're at this point, (b) applies. Therefore,
* check if we're being continued, and if so, bail.
* (in case (a), we should let the code finish and
* we will bail out in pthread_spinunlock()).
*/
if (thread->pt_next != NULL) {
PTHREADD_ADD(PTHREADD_SPINPREEMPT);
pthread__switch(thread, thread->pt_next);
}
/* try again */
count = nspins;
SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n",
thread, thread->pt_spinlocks));
++thread->pt_spinlocks;
} while (/*CONSTCOND*/1);
PTHREADD_ADD(PTHREADD_SPINLOCKS);
/* Got it! We're out of here. */
}
int
pthread_spintrylock(pthread_t thread, pthread_spin_t *lock)
{
int ret;
SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n",
thread, thread->pt_spinlocks));
++thread->pt_spinlocks;
ret = pthread__simple_lock_try(lock);
if (ret == 0) {
SDPRINTF(("(pthread_spintrylock %p) decrementing spinlock from %d\n",
thread, thread->pt_spinlocks));
--thread->pt_spinlocks;
/* See above. */
if (thread->pt_next != NULL) {
PTHREADD_ADD(PTHREADD_SPINPREEMPT);
pthread__switch(thread, thread->pt_next);
}
}
return ret;
}
void
pthread_spinunlock(pthread_t thread, pthread_spin_t *lock)
{
pthread__simple_unlock(lock);
SDPRINTF(("(pthread_spinunlock %p) decrementing spinlock %p (count %d)\n",
thread, lock, thread->pt_spinlocks));
--thread->pt_spinlocks;
#ifdef PTHREAD_SPIN_DEBUG
pthread__assert(thread->pt_spinlocks >= 0);
#endif
PTHREADD_ADD(PTHREADD_SPINUNLOCKS);
/*
* If we were preempted while holding a spinlock, the
* scheduler will notice this and continue us. To be good
* citzens, we must now get out of here if that was our
* last spinlock.
* XXX when will we ever have more than one?
*/
if ((thread->pt_spinlocks == 0) && (thread->pt_next != NULL)) {
PTHREADD_ADD(PTHREADD_SPINPREEMPT);
pthread__switch(thread, thread->pt_next);
}
}
/*
* Public (POSIX-specified) spinlocks.
* These don't interact with the spin-preemption code, nor do they
* perform any adaptive sleeping.
*/
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)
/* spin */ ;
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;
}
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