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0a3fa43c7e
freebsd/lib/libpthread/thread/thr_cond.c
Jason Evans 0a3fa43c7e Implement continuations to correctly handle [sig|_]longjmp() inside of a 
signal handler.  Explicitly check for jumps to anywhere other than the
current stack, since such jumps are undefined according to POSIX.

While we're at it, convert thread cancellation to use continuations, since
it's cleaner than the original cancellation code.

Avoid delivering a signal to a thread twice.  This was a pre-existing bug,
but was likely unexposed until these other changes were made.

Defer signals generated by pthread_kill() so that they can be delivered on
the appropriate stack.  deischen claims that this is unnecessary, which is
likely true, but without this change, pthread_kill() can cause undefined
priority queue states and/or PANICs in [sig|_]longjmp(), so I'm leaving
this in for now.  To compile this code out and exercise the bug, define
the _NO_UNDISPATCH cpp macro.  Defining _PTHREADS_INVARIANTS as well will
cause earlier crashes.

PR:			kern/14685
Collaboration with:	deischen
2000-01-19 07:04:50 +00:00

631 lines
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/*
* 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.
*
* $FreeBSD$
*/
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"
/*
* Prototypes
*/
static inline pthread_t cond_queue_deq(pthread_cond_t);
static inline void cond_queue_remove(pthread_cond_t, pthread_t);
static inline void cond_queue_enq(pthread_cond_t, pthread_t);
/* Reinitialize a condition variable to defaults. */
int
_cond_reinit(pthread_cond_t * cond)
{
int ret = 0;
if (cond == NULL)
ret = EINVAL;
else if (*cond == NULL)
ret = pthread_cond_init(cond, NULL);
else {
/*
* 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;
memset(&(*cond)->lock, 0, sizeof((*cond)->lock));
}
return (ret);
}
int
pthread_cond_init(pthread_cond_t * cond, const pthread_condattr_t * cond_attr)
{
enum pthread_cond_type type;
pthread_cond_t pcond;
int rval = 0;
if (cond == NULL)
rval = EINVAL;
else {
/*
* Check if a pointer to a condition variable attribute
* structure was passed by the caller:
*/
if (cond_attr != NULL && *cond_attr != NULL) {
/* Default to a fast condition variable: */
type = (*cond_attr)->c_type;
} else {
/* Default to a fast condition variable: */
type = COND_TYPE_FAST;
}
/* Process according to condition variable type: */
switch (type) {
/* Fast condition variable: */
case COND_TYPE_FAST:
/* Nothing to do here. */
break;
/* Trap invalid condition variable types: */
default:
/* Return an invalid argument error: */
rval = EINVAL;
break;
}
/* Check for no errors: */
if (rval == 0) {
if ((pcond = (pthread_cond_t)
malloc(sizeof(struct pthread_cond))) == NULL) {
rval = ENOMEM;
} else {
/*
* Initialise the condition variable
* structure:
*/
TAILQ_INIT(&pcond->c_queue);
pcond->c_flags |= COND_FLAGS_INITED;
pcond->c_type = type;
pcond->c_mutex = NULL;
memset(&pcond->lock,0,sizeof(pcond->lock));
*cond = pcond;
}
}
}
/* Return the completion status: */
return (rval);
}
int
pthread_cond_destroy(pthread_cond_t * cond)
{
int rval = 0;
if (cond == NULL || *cond == NULL)
rval = EINVAL;
else {
/* Lock the condition variable structure: */
_SPINLOCK(&(*cond)->lock);
/*
* 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 the completion status: */
return (rval);
}
int
pthread_cond_wait(pthread_cond_t * cond, pthread_mutex_t * mutex)
{
int rval = 0;
int interrupted = 0;
if (cond == NULL)
rval = EINVAL;
/*
* If the condition variable is statically initialized,
* perform the dynamic initialization:
*/
else if (*cond != NULL ||
(rval = pthread_cond_init(cond,NULL)) == 0) {
_thread_enter_cancellation_point();
/* Lock the condition variable structure: */
_SPINLOCK(&(*cond)->lock);
/*
* 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;
}
/* Process according to condition variable type: */
switch ((*cond)->c_type) {
/* Fast condition variable: */
case COND_TYPE_FAST:
if ((mutex == NULL) || (((*cond)->c_mutex != NULL) &&
((*cond)->c_mutex != *mutex))) {
/* Unlock the condition variable structure: */
_SPINUNLOCK(&(*cond)->lock);
/* Return invalid argument error: */
rval = EINVAL;
} else {
/* Reset the timeout and interrupted flags: */
_thread_run->timeout = 0;
_thread_run->interrupted = 0;
/*
* Queue the running thread for the condition
* variable:
*/
cond_queue_enq(*cond, _thread_run);
/* Remember the mutex that is being used: */
(*cond)->c_mutex = *mutex;
/* Wait forever: */
_thread_run->wakeup_time.tv_sec = -1;
/* Unlock the mutex: */
if ((rval = _mutex_cv_unlock(mutex)) != 0) {
/*
* Cannot unlock the mutex, so remove
* the running thread from the condition
* variable queue:
*/
cond_queue_remove(*cond, _thread_run);
/* Check for no more waiters: */
if (TAILQ_FIRST(&(*cond)->c_queue) ==
NULL)
(*cond)->c_mutex = NULL;
/* Unlock the condition variable structure: */
_SPINUNLOCK(&(*cond)->lock);
}
else {
/*
* Schedule the next thread and unlock
* the condition variable structure:
*/
_thread_kern_sched_state_unlock(PS_COND_WAIT,
&(*cond)->lock, __FILE__, __LINE__);
if (_thread_run->interrupted != 0) {
/*
* Remember that this thread
* was interrupted:
*/
interrupted = 1;
/*
* Lock the condition variable
* while removing the thread.
*/
_SPINLOCK(&(*cond)->lock);
cond_queue_remove(*cond,
_thread_run);
/* Check for no more waiters: */
if (TAILQ_FIRST(&(*cond)->c_queue) == NULL)
(*cond)->c_mutex = NULL;
_SPINUNLOCK(&(*cond)->lock);
}
/*
* Note that even though this thread may have
* been canceled, POSIX requires that the mutex
* be reaquired prior to cancellation.
*/
rval = _mutex_cv_lock(mutex);
}
}
break;
/* Trap invalid condition variable types: */
default:
/* Unlock the condition variable structure: */
_SPINUNLOCK(&(*cond)->lock);
/* Return an invalid argument error: */
rval = EINVAL;
break;
}
if (interrupted != 0 && _thread_run->continuation != NULL)
_thread_run->continuation((void *) _thread_run);
_thread_leave_cancellation_point();
}
/* Return the completion status: */
return (rval);
}
int
pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex,
const struct timespec * abstime)
{
int rval = 0;
int interrupted = 0;
if (cond == NULL || abstime == NULL)
rval = EINVAL;
if (abstime->tv_sec < 0 ||
abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000) {
errno = EINVAL;
return (-1);
}
/*
* If the condition variable is statically initialized,
* perform the dynamic initialization:
*/
if (*cond != NULL ||
(rval = pthread_cond_init(cond,NULL)) == 0) {
_thread_enter_cancellation_point();
/* Lock the condition variable structure: */
_SPINLOCK(&(*cond)->lock);
/*
* 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;
}
/* Process according to condition variable type: */
switch ((*cond)->c_type) {
/* Fast condition variable: */
case COND_TYPE_FAST:
if ((mutex == NULL) || (((*cond)->c_mutex != NULL) &&
((*cond)->c_mutex != *mutex))) {
/* Return invalid argument error: */
rval = EINVAL;
/* Unlock the condition variable structure: */
_SPINUNLOCK(&(*cond)->lock);
} else {
/* Set the wakeup time: */
_thread_run->wakeup_time.tv_sec =
abstime->tv_sec;
_thread_run->wakeup_time.tv_nsec =
abstime->tv_nsec;
/* Reset the timeout and interrupted flags: */
_thread_run->timeout = 0;
_thread_run->interrupted = 0;
/*
* Queue the running thread for the condition
* variable:
*/
cond_queue_enq(*cond, _thread_run);
/* Remember the mutex that is being used: */
(*cond)->c_mutex = *mutex;
/* Unlock the mutex: */
if ((rval = _mutex_cv_unlock(mutex)) != 0) {
/*
* Cannot unlock the mutex, so remove
* the running thread from the condition
* variable queue:
*/
cond_queue_remove(*cond, _thread_run);
/* Check for no more waiters: */
if (TAILQ_FIRST(&(*cond)->c_queue) == NULL)
(*cond)->c_mutex = NULL;
/* Unlock the condition variable structure: */
_SPINUNLOCK(&(*cond)->lock);
} else {
/*
* Schedule the next thread and unlock
* the condition variable structure:
*/
_thread_kern_sched_state_unlock(PS_COND_WAIT,
&(*cond)->lock, __FILE__, __LINE__);
/*
* Check if the wait timedout or was
* interrupted (canceled):
*/
if ((_thread_run->timeout == 0) &&
(_thread_run->interrupted == 0)) {
/* Lock the mutex: */
rval = _mutex_cv_lock(mutex);
} else {
/*
* Remember if this thread was
* interrupted:
*/
interrupted = _thread_run->interrupted;
/* Lock the condition variable structure: */
_SPINLOCK(&(*cond)->lock);
/*
* The wait timed out; remove
* the thread from the condition
* variable queue:
*/
cond_queue_remove(*cond,
_thread_run);
/* Check for no more waiters: */
if (TAILQ_FIRST(&(*cond)->c_queue) == NULL)
(*cond)->c_mutex = NULL;
/* Unock the condition variable structure: */
_SPINUNLOCK(&(*cond)->lock);
/* Return a timeout error: */
rval = ETIMEDOUT;
/*
* Lock the mutex and ignore any
* errors. Note that even though
* this thread may have been
* canceled, POSIX requires that
* the mutex be reaquired prior
* to cancellation.
*/
(void)_mutex_cv_lock(mutex);
}
}
}
break;
/* Trap invalid condition variable types: */
default:
/* Unlock the condition variable structure: */
_SPINUNLOCK(&(*cond)->lock);
/* Return an invalid argument error: */
rval = EINVAL;
break;
}
if (interrupted != 0 && _thread_run->continuation != NULL)
_thread_run->continuation((void *) _thread_run);
_thread_leave_cancellation_point();
}
/* Return the completion status: */
return (rval);
}
int
pthread_cond_signal(pthread_cond_t * cond)
{
int rval = 0;
pthread_t pthread;
if (cond == NULL || *cond == NULL)
rval = EINVAL;
else {
/*
* Defer signals to protect the scheduling queues
* from access by the signal handler:
*/
_thread_kern_sig_defer();
/* Lock the condition variable structure: */
_SPINLOCK(&(*cond)->lock);
/* Process according to condition variable type: */
switch ((*cond)->c_type) {
/* Fast condition variable: */
case COND_TYPE_FAST:
if ((pthread = cond_queue_deq(*cond)) != NULL)
/* Allow the thread to run: */
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
/* Check for no more waiters: */
if (TAILQ_FIRST(&(*cond)->c_queue) == NULL)
(*cond)->c_mutex = NULL;
break;
/* Trap invalid condition variable types: */
default:
/* Return an invalid argument error: */
rval = EINVAL;
break;
}
/* Unlock the condition variable structure: */
_SPINUNLOCK(&(*cond)->lock);
/*
* Undefer and handle pending signals, yielding if
* necessary:
*/
_thread_kern_sig_undefer();
}
/* Return the completion status: */
return (rval);
}
int
pthread_cond_broadcast(pthread_cond_t * cond)
{
int rval = 0;
pthread_t pthread;
if (cond == NULL || *cond == NULL)
rval = EINVAL;
else {
/*
* Defer signals to protect the scheduling queues
* from access by the signal handler:
*/
_thread_kern_sig_defer();
/* Lock the condition variable structure: */
_SPINLOCK(&(*cond)->lock);
/* Process according to condition variable type: */
switch ((*cond)->c_type) {
/* Fast condition variable: */
case COND_TYPE_FAST:
/*
* Enter a loop to bring all threads off the
* condition queue:
*/
while ((pthread = cond_queue_deq(*cond)) != NULL) {
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
}
/* There are no more waiting threads: */
(*cond)->c_mutex = NULL;
break;
/* Trap invalid condition variable types: */
default:
/* Return an invalid argument error: */
rval = EINVAL;
break;
}
/* Unlock the condition variable structure: */
_SPINUNLOCK(&(*cond)->lock);
/*
* Undefer and handle pending signals, yielding if
* necessary:
*/
_thread_kern_sig_undefer();
}
/* Return the completion status: */
return (rval);
}
/*
* Dequeue a waiting thread from the head of a condition queue in
* descending priority order.
*/
static inline pthread_t
cond_queue_deq(pthread_cond_t cond)
{
pthread_t pthread;
while ((pthread = TAILQ_FIRST(&cond->c_queue)) != NULL) {
TAILQ_REMOVE(&cond->c_queue, pthread, qe);
pthread->flags &= ~PTHREAD_FLAGS_IN_CONDQ;
if ((pthread->timeout == 0) && (pthread->interrupted == 0))
/*
* Only exit the loop when we find a thread
* that hasn't timed out or been canceled;
* those threads are already running and don't
* need their run state changed.
*/
break;
}
return(pthread);
}
/*
* Remove a waiting thread from a condition queue in descending priority
* order.
*/
static inline 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, qe);
pthread->flags &= ~PTHREAD_FLAGS_IN_CONDQ;
}
}
/*
* Enqueue a waiting thread to a condition queue in descending priority
* order.
*/
static inline void
cond_queue_enq(pthread_cond_t cond, pthread_t pthread)
{
pthread_t tid = TAILQ_LAST(&cond->c_queue, cond_head);
/*
* 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, qe);
else {
tid = TAILQ_FIRST(&cond->c_queue);
while (pthread->active_priority <= tid->active_priority)
tid = TAILQ_NEXT(tid, qe);
TAILQ_INSERT_BEFORE(tid, pthread, qe);
}
pthread->flags |= PTHREAD_FLAGS_IN_CONDQ;
}
#endif
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