FreeBSD-5.3/lib/libthr/thread/thr_cond.c
/*
* Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
* All rights reserved.
*
* 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 John Birrell.
* 4. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL 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 AUTHOR 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.
*
* $FreeBSD: src/lib/libthr/thread/thr_cond.c,v 1.15 2004/07/02 00:40:07 marcel Exp $
*/
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <pthread.h>
#include "thr_private.h"
/*
* Proctect two different threads calling a pthread_cond_* function
* from accidentally initializing the condition variable twice.
*/
static spinlock_t static_cond_lock = _SPINLOCK_INITIALIZER;
/*
* Prototypes
*/
static inline int cond_init(pthread_cond_t *);
static pthread_t cond_queue_deq(pthread_cond_t);
static void cond_queue_remove(pthread_cond_t, pthread_t);
static void cond_queue_enq(pthread_cond_t, pthread_t);
static int cond_signal(pthread_cond_t *, int);
static int cond_wait_common(pthread_cond_t *,
pthread_mutex_t *, const struct timespec *);
__weak_reference(_pthread_cond_init, pthread_cond_init);
__weak_reference(_pthread_cond_destroy, pthread_cond_destroy);
__weak_reference(_pthread_cond_wait, pthread_cond_wait);
__weak_reference(_pthread_cond_timedwait, pthread_cond_timedwait);
__weak_reference(_pthread_cond_signal, pthread_cond_signal);
__weak_reference(_pthread_cond_broadcast, pthread_cond_broadcast);
#define COND_LOCK(c) \
do { \
if (umtx_lock(&(c)->c_lock, curthread->thr_id)) \
abort(); \
} while (0)
#define COND_UNLOCK(c) \
do { \
if (umtx_unlock(&(c)->c_lock, curthread->thr_id)) \
abort(); \
} while (0)
/* Reinitialize a condition variable to defaults. */
int
_cond_reinit(pthread_cond_t *cond)
{
if (cond == NULL)
return (EINVAL);
if (*cond == NULL)
return (pthread_cond_init(cond, NULL));
/*
* Initialize the condition variable structure:
*/
TAILQ_INIT(&(*cond)->c_queue);
(*cond)->c_flags = COND_FLAGS_INITED;
(*cond)->c_type = COND_TYPE_FAST;
(*cond)->c_mutex = NULL;
(*cond)->c_seqno = 0;
bzero(&(*cond)->c_lock, sizeof((*cond)->c_lock));
return (0);
}
int
_pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
{
enum pthread_cond_type type;
pthread_cond_t pcond;
if (cond == NULL)
return (EINVAL);
/*
* Check if a pointer to a condition variable attribute
* structure was passed by the caller:
*/
if (cond_attr != NULL && *cond_attr != NULL)
type = (*cond_attr)->c_type;
else
/* Default to a fast condition variable: */
type = COND_TYPE_FAST;
/* Process according to condition variable type: */
switch (type) {
case COND_TYPE_FAST:
break;
default:
return (EINVAL);
break;
}
if ((pcond = (pthread_cond_t)
malloc(sizeof(struct pthread_cond))) == NULL)
return (ENOMEM);
/*
* Initialise the condition variable
* structure:
*/
TAILQ_INIT(&pcond->c_queue);
pcond->c_flags |= COND_FLAGS_INITED;
pcond->c_type = type;
pcond->c_mutex = NULL;
pcond->c_seqno = 0;
bzero(&pcond->c_lock, sizeof(pcond->c_lock));
*cond = pcond;
return (0);
}
int
_pthread_cond_destroy(pthread_cond_t *cond)
{
/*
* Short circuit for a statically initialized condvar
* that is being destroyed without having been used.
*/
if (*cond == PTHREAD_COND_INITIALIZER)
return (0);
COND_LOCK(*cond);
/*
* Free the memory allocated for the condition
* variable structure:
*/
free(*cond);
/*
* NULL the caller's pointer now that the condition
* variable has been destroyed:
*/
*cond = NULL;
return (0);
}
int
_pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
{
int rval;
rval = cond_wait_common(cond, mutex, NULL);
/* This should never happen. */
if (rval == ETIMEDOUT)
abort();
return (rval);
}
int
_pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex,
const struct timespec * abstime)
{
if (abstime == NULL || abstime->tv_nsec >= 1000000000)
return (EINVAL);
return (cond_wait_common(cond, mutex, abstime));
}
static int
cond_wait_common(pthread_cond_t * cond, pthread_mutex_t * mutex,
const struct timespec * abstime)
{
int rval = 0;
int mtxrval;
if (cond == NULL)
return (EINVAL);
/*
* If the condition variable is statically initialized, perform dynamic
* initialization.
*/
if (*cond == PTHREAD_COND_INITIALIZER && (rval = cond_init(cond)) != 0)
return (rval);
if ((*cond)->c_type != COND_TYPE_FAST)
return (EINVAL);
COND_LOCK(*cond);
/*
* If the condvar was statically allocated, properly
* initialize the tail queue.
*/
if (((*cond)->c_flags & COND_FLAGS_INITED) == 0) {
TAILQ_INIT(&(*cond)->c_queue);
(*cond)->c_flags |= COND_FLAGS_INITED;
}
if ((mutex == NULL) || (((*cond)->c_mutex != NULL) &&
((*cond)->c_mutex != *mutex))) {
COND_UNLOCK(*cond);
return (EINVAL);
}
/* Remember the mutex */
(*cond)->c_mutex = *mutex;
_thread_enter_cancellation_point();
if ((rval = _mutex_cv_unlock(mutex)) != 0) {
if (rval == -1){
printf("mutex unlock by condvar failed!");
fflush(stdout);
abort();
}
_thread_leave_cancellation_point();
COND_UNLOCK(*cond);
return (rval);
}
/*
* We need to protect the queue operations. It also
* protects the pthread flag field. This is
* dropped before calling _thread_suspend() and reaquired
* when we return.
*/
PTHREAD_LOCK(curthread);
/*
* Queue the running thread on the condition
* variable and wait to be signaled.
*/
cond_queue_enq(*cond, curthread);
do {
PTHREAD_UNLOCK(curthread);
COND_UNLOCK(*cond);
if (curthread->cancellation == CS_PENDING) {
/*
* Posix says we must lock the mutex
* even if we're being canceled.
*/
_mutex_cv_lock(mutex);
_thread_leave_cancellation_point();
PANIC("Shouldn't have come back.");
}
rval = _thread_suspend(curthread, (struct timespec *)abstime);
if (rval != 0 && rval != ETIMEDOUT && rval != EINTR) {
printf("thread suspend returned an invalid value");
fflush(stdout);
abort();
}
COND_LOCK(*cond);
PTHREAD_LOCK(curthread);
if (rval == ETIMEDOUT) {
/*
* Condition may have been signaled between the
* time the thread timed out and locked the condvar.
* If it wasn't, manually remove it from the queue.
*/
if ((curthread->flags & PTHREAD_FLAGS_IN_CONDQ) == 0)
rval = 0;
else
cond_queue_remove(*cond, curthread);
}
} while ((curthread->flags & PTHREAD_FLAGS_IN_CONDQ) != 0);
PTHREAD_UNLOCK(curthread);
COND_UNLOCK(*cond);
mtxrval = _mutex_cv_lock(mutex);
/* If the mutex failed return that error. */
if (mtxrval == -1) {
printf("mutex lock from condvar failed!");
fflush(stdout);
abort();
}
if (mtxrval != 0)
rval = mtxrval;
_thread_leave_cancellation_point();
return (rval);
}
int
_pthread_cond_signal(pthread_cond_t * cond)
{
return (cond_signal(cond, 0));
}
int
_pthread_cond_broadcast(pthread_cond_t * cond)
{
return (cond_signal(cond, 1));
}
static int
cond_signal(pthread_cond_t * cond, int broadcast)
{
int rval = 0;
pthread_t pthread;
if (cond == NULL)
return (EINVAL);
/*
* If the condition variable is statically initialized, perform dynamic
* initialization.
*/
if (*cond == PTHREAD_COND_INITIALIZER && (rval = cond_init(cond)) != 0)
return (rval);
if ((*cond)->c_type != COND_TYPE_FAST)
return (EINVAL);
COND_LOCK(*cond);
/*
* Enter a loop to bring all (or only one) threads off the
* condition queue:
*/
do {
/*
* Wake up the signaled thread. It will be returned
* to us locked.
*/
if ((pthread = cond_queue_deq(*cond)) != NULL) {
PTHREAD_WAKE(pthread);
PTHREAD_UNLOCK(pthread);
}
} while (broadcast && pthread != NULL);
COND_UNLOCK(*cond);
return (rval);
}
void
_cond_wait_backout(pthread_t pthread)
{
pthread_cond_t cond;
cond = pthread->data.cond;
if (cond == NULL)
return;
/* Process according to condition variable type: */
switch (cond->c_type) {
/* Fast condition variable: */
case COND_TYPE_FAST:
cond_queue_remove(cond, pthread);
break;
default:
break;
}
}
/*
* Dequeue a waiting thread from the head of a condition queue in
* descending priority order.
*/
static pthread_t
cond_queue_deq(pthread_cond_t cond)
{
pthread_t pthread;
while ((pthread = TAILQ_FIRST(&cond->c_queue)) != NULL) {
PTHREAD_LOCK(pthread);
cond_queue_remove(cond, pthread);
/*
* Only exit the loop when we find a thread
* that hasn't been canceled.
*/
if (pthread->cancellation == CS_NULL)
break;
else
PTHREAD_UNLOCK(pthread);
}
return(pthread);
}
/*
* Remove a waiting thread from a condition queue in descending priority
* order.
*/
static void
cond_queue_remove(pthread_cond_t cond, pthread_t pthread)
{
/*
* Because pthread_cond_timedwait() can timeout as well
* as be signaled by another thread, it is necessary to
* guard against removing the thread from the queue if
* it isn't in the queue.
*/
if (pthread->flags & PTHREAD_FLAGS_IN_CONDQ) {
TAILQ_REMOVE(&cond->c_queue, pthread, sqe);
pthread->flags &= ~PTHREAD_FLAGS_IN_CONDQ;
}
/* Check for no more waiters. */
if (TAILQ_FIRST(&cond->c_queue) == NULL)
cond->c_mutex = NULL;
}
/*
* Enqueue a waiting thread to a condition queue in descending priority
* order.
*/
static void
cond_queue_enq(pthread_cond_t cond, pthread_t pthread)
{
pthread_t tid = TAILQ_LAST(&cond->c_queue, cond_head);
char *name;
name = pthread->name ? pthread->name : "unknown";
if ((pthread->flags & PTHREAD_FLAGS_IN_CONDQ) != 0)
_thread_printf(2, "Thread (%s:%ld) already on condq\n",
pthread->name, pthread->thr_id);
if ((pthread->flags & PTHREAD_FLAGS_IN_MUTEXQ) != 0)
_thread_printf(2, "Thread (%s:%ld) already on mutexq\n",
pthread->name, pthread->thr_id);
PTHREAD_ASSERT_NOT_IN_SYNCQ(pthread);
/*
* For the common case of all threads having equal priority,
* we perform a quick check against the priority of the thread
* at the tail of the queue.
*/
if ((tid == NULL) || (pthread->active_priority <= tid->active_priority))
TAILQ_INSERT_TAIL(&cond->c_queue, pthread, sqe);
else {
tid = TAILQ_FIRST(&cond->c_queue);
while (pthread->active_priority <= tid->active_priority)
tid = TAILQ_NEXT(tid, sqe);
TAILQ_INSERT_BEFORE(tid, pthread, sqe);
}
pthread->flags |= PTHREAD_FLAGS_IN_CONDQ;
pthread->data.cond = cond;
}
static inline int
cond_init(pthread_cond_t *cond)
{
int error = 0;
_SPINLOCK(&static_cond_lock);
if (*cond == PTHREAD_COND_INITIALIZER)
error = _pthread_cond_init(cond, NULL);
_SPINUNLOCK(&static_cond_lock);
return (error);
}