rthread_sync.c

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Author : pirofti
Date : 2018-04-24 16:28:42
Hash : bda456cc
Message : Validate timespec and return ECANCELED when interrupted with SA_RESTART. Discussing with mpi@ and guenther@, we decided to first fix the existing semaphore implementation with regards to SA_RESTART and POSIX compliant returns in the case where we deal with restartable signals. Currently we return EINTR everywhere which is mostly incorrect as the user can not know if she needs to recall the syscall or not. Return ECANCELED to signal that SA_RESTART was set and EINTR otherwise. Regression tests pass and so does the posixsuite. Timespec validation bits are needed to pass the later. OK mpi@, guenther@
lib/libc/thread/rthread_sync.c
/*	$OpenBSD: rthread_sync.c,v 1.5 2018/04/24 16:28:42 pirofti Exp $ */
/*
 * Copyright (c) 2004,2005 Ted Unangst <tedu@openbsd.org>
 * Copyright (c) 2012 Philip Guenther <guenther@openbsd.org>
 * All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
/*
 * Mutexes and conditions - synchronization functions.
 */

#include <assert.h>
#include <errno.h>
#include <pthread.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "rthread.h"
#include "cancel.h"		/* in libc/include */

static _atomic_lock_t static_init_lock = _SPINLOCK_UNLOCKED;

/*
 * mutexen
 */
int
pthread_mutex_init(pthread_mutex_t *mutexp, const pthread_mutexattr_t *attr)
{
	struct pthread_mutex *mutex;

	mutex = calloc(1, sizeof(*mutex));
	if (!mutex)
		return (errno);
	mutex->lock = _SPINLOCK_UNLOCKED;
	TAILQ_INIT(&mutex->lockers);
	if (attr == NULL) {
		mutex->type = PTHREAD_MUTEX_DEFAULT;
		mutex->prioceiling = -1;
	} else {
		mutex->type = (*attr)->ma_type;
		mutex->prioceiling = (*attr)->ma_protocol ==
		    PTHREAD_PRIO_PROTECT ? (*attr)->ma_prioceiling : -1;
	}
	*mutexp = mutex;

	return (0);
}
DEF_STRONG(pthread_mutex_init);

int
pthread_mutex_destroy(pthread_mutex_t *mutexp)
{
	struct pthread_mutex *mutex;

	assert(mutexp);
	mutex = (struct pthread_mutex *)*mutexp;
	if (mutex) {
		if (mutex->count || mutex->owner != NULL ||
		    !TAILQ_EMPTY(&mutex->lockers)) {
#define MSG "pthread_mutex_destroy on mutex with waiters!\n"
			write(2, MSG, sizeof(MSG) - 1);
#undef MSG
			return (EBUSY);
		}
		free(mutex);
		*mutexp = NULL;
	}
	return (0);
}
DEF_STRONG(pthread_mutex_destroy);

static int
_rthread_mutex_lock(pthread_mutex_t *mutexp, int trywait,
    const struct timespec *abstime)
{
	struct pthread_mutex *mutex;
	pthread_t self = pthread_self();
	int ret = 0;

	/*
	 * If the mutex is statically initialized, perform the dynamic
	 * initialization. Note: _thread_mutex_lock() in libc requires
	 * _rthread_mutex_lock() to perform the mutex init when *mutexp
	 * is NULL.
	 */
	if (*mutexp == NULL) {
		_spinlock(&static_init_lock);
		if (*mutexp == NULL)
			ret = pthread_mutex_init(mutexp, NULL);
		_spinunlock(&static_init_lock);
		if (ret != 0)
			return (EINVAL);
	}
	mutex = (struct pthread_mutex *)*mutexp;

	_rthread_debug(5, "%p: mutex_lock %p\n", (void *)self, (void *)mutex);
	_spinlock(&mutex->lock);
	if (mutex->owner == NULL && TAILQ_EMPTY(&mutex->lockers)) {
		assert(mutex->count == 0);
		mutex->owner = self;
	} else if (mutex->owner == self) {
		assert(mutex->count > 0);

		/* already owner?  handle recursive behavior */
		if (mutex->type != PTHREAD_MUTEX_RECURSIVE)
		{
			if (trywait ||
			    mutex->type == PTHREAD_MUTEX_ERRORCHECK) {
				_spinunlock(&mutex->lock);
				return (trywait ? EBUSY : EDEADLK);
			}

			/* self-deadlock is disallowed by strict */
			if (mutex->type == PTHREAD_MUTEX_STRICT_NP &&
			    abstime == NULL)
				abort();

			/* self-deadlock, possibly until timeout */
			while (__thrsleep(self, CLOCK_REALTIME, abstime,
			    &mutex->lock, NULL) != EWOULDBLOCK)
				_spinlock(&mutex->lock);
			return (ETIMEDOUT);
		}
		if (mutex->count == INT_MAX) {
			_spinunlock(&mutex->lock);
			return (EAGAIN);
		}
	} else if (trywait) {
		/* try failed */
		_spinunlock(&mutex->lock);
		return (EBUSY);
	} else {
		/* add to the wait queue and block until at the head */
		TAILQ_INSERT_TAIL(&mutex->lockers, self, waiting);
		while (mutex->owner != self) {
			ret = __thrsleep(self, CLOCK_REALTIME, abstime,
			    &mutex->lock, NULL);
			_spinlock(&mutex->lock);
			assert(mutex->owner != NULL);
			if (ret == EWOULDBLOCK) {
				if (mutex->owner == self)
					break;
				TAILQ_REMOVE(&mutex->lockers, self, waiting);
				_spinunlock(&mutex->lock);
				return (ETIMEDOUT);
			}
		}
	}

	mutex->count++;
	_spinunlock(&mutex->lock);

	return (0);
}

int
pthread_mutex_lock(pthread_mutex_t *p)
{
	return (_rthread_mutex_lock(p, 0, NULL));
}
DEF_STRONG(pthread_mutex_lock);

int
pthread_mutex_trylock(pthread_mutex_t *p)
{
	return (_rthread_mutex_lock(p, 1, NULL));
}

int
pthread_mutex_timedlock(pthread_mutex_t *p, const struct timespec *abstime)
{
	return (_rthread_mutex_lock(p, 0, abstime));
}

int
pthread_mutex_unlock(pthread_mutex_t *mutexp)
{
	pthread_t self = pthread_self();
	struct pthread_mutex *mutex = (struct pthread_mutex *)*mutexp;

	_rthread_debug(5, "%p: mutex_unlock %p\n", (void *)self,
	    (void *)mutex);

	if (mutex == NULL)
#if PTHREAD_MUTEX_DEFAULT == PTHREAD_MUTEX_ERRORCHECK
		return (EPERM);
#elif PTHREAD_MUTEX_DEFAULT == PTHREAD_MUTEX_NORMAL
		return(0);
#else
		abort();
#endif

	if (mutex->owner != self) {
		if (mutex->type == PTHREAD_MUTEX_ERRORCHECK ||
		    mutex->type == PTHREAD_MUTEX_RECURSIVE)
			return (EPERM);
		else {
			/*
			 * For mutex type NORMAL our undefined behavior for
			 * unlocking an unlocked mutex is to succeed without
			 * error.  All other undefined behaviors are to
			 * abort() immediately.
			 */
			if (mutex->owner == NULL &&
			    mutex->type == PTHREAD_MUTEX_NORMAL)
				return (0);
			else
				abort();
		}
	}

	if (--mutex->count == 0) {
		pthread_t next;

		_spinlock(&mutex->lock);
		mutex->owner = next = TAILQ_FIRST(&mutex->lockers);
		if (next != NULL)
			TAILQ_REMOVE(&mutex->lockers, next, waiting);
		_spinunlock(&mutex->lock);
		if (next != NULL)
			__thrwakeup(next, 1);
	}

	return (0);
}
DEF_STRONG(pthread_mutex_unlock);

/*
 * condition variables
 */
int
pthread_cond_init(pthread_cond_t *condp, const pthread_condattr_t *attr)
{
	pthread_cond_t cond;

	cond = calloc(1, sizeof(*cond));
	if (!cond)
		return (errno);
	cond->lock = _SPINLOCK_UNLOCKED;
	TAILQ_INIT(&cond->waiters);
	if (attr == NULL)
		cond->clock = CLOCK_REALTIME;
	else
		cond->clock = (*attr)->ca_clock;
	*condp = cond;

	return (0);
}
DEF_STRONG(pthread_cond_init);

int
pthread_cond_destroy(pthread_cond_t *condp)
{
	pthread_cond_t cond;

	assert(condp);
	cond = *condp;
	if (cond) {
		if (!TAILQ_EMPTY(&cond->waiters)) {
#define MSG "pthread_cond_destroy on condvar with waiters!\n"
			write(2, MSG, sizeof(MSG) - 1);
#undef MSG
			return (EBUSY);
		}
		free(cond);
	}
	*condp = NULL;

	return (0);
}

int
pthread_cond_timedwait(pthread_cond_t *condp, pthread_mutex_t *mutexp,
    const struct timespec *abstime)
{
	pthread_cond_t cond;
	struct pthread_mutex *mutex = (struct pthread_mutex *)*mutexp;
	struct tib *tib = TIB_GET();
	pthread_t self = tib->tib_thread;
	pthread_t next;
	int mutex_count;
	int canceled = 0;
	int rv = 0;
	int error;
	PREP_CANCEL_POINT(tib);

	if (!*condp)
		if ((error = pthread_cond_init(condp, NULL)))
			return (error);
	cond = *condp;
	_rthread_debug(5, "%p: cond_timed %p,%p\n", (void *)self,
	    (void *)cond, (void *)mutex);

	if (mutex == NULL)
#if PTHREAD_MUTEX_DEFAULT == PTHREAD_MUTEX_ERRORCHECK
		return (EPERM);
#else
		abort();
#endif

	if (mutex->owner != self) {
		if (mutex->type == PTHREAD_MUTEX_ERRORCHECK)
			return (EPERM);
		else
			abort();
	}

	if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
	    abstime->tv_nsec >= 1000000000)
		return (EINVAL);

	ENTER_DELAYED_CANCEL_POINT(tib, self);

	_spinlock(&cond->lock);

	/* mark the condvar as being associated with this mutex */
	if (cond->mutex == NULL) {
		cond->mutex = mutex;
		assert(TAILQ_EMPTY(&cond->waiters));
	} else if (cond->mutex != mutex) {
		assert(cond->mutex == mutex);
		_spinunlock(&cond->lock);
		LEAVE_CANCEL_POINT_INNER(tib, 1);
		return (EINVAL);
	} else
		assert(! TAILQ_EMPTY(&cond->waiters));

	/* snag the count in case this is a recursive mutex */
	mutex_count = mutex->count;

	/* transfer from the mutex queue to the condvar queue */
	_spinlock(&mutex->lock);
	self->blocking_cond = cond;
	TAILQ_INSERT_TAIL(&cond->waiters, self, waiting);
	_spinunlock(&cond->lock);

	/* wake the next guy blocked on the mutex */
	mutex->count = 0;
	mutex->owner = next = TAILQ_FIRST(&mutex->lockers);
	if (next != NULL) {
		TAILQ_REMOVE(&mutex->lockers, next, waiting);
		__thrwakeup(next, 1);
	}

	/* wait until we're the owner of the mutex again */
	while (mutex->owner != self) {
		error = __thrsleep(self, cond->clock, abstime,
		    &mutex->lock, &self->delayed_cancel);

		/*
		 * If abstime == NULL, then we're definitely waiting
		 * on the mutex instead of the condvar, and are
		 * just waiting for mutex ownership, regardless of
		 * why we woke up.
		 */
		if (abstime == NULL) {
			_spinlock(&mutex->lock);
			continue;
		}

		/*
		 * If we took a normal signal (not from
		 * cancellation) then we should just go back to
		 * sleep without changing state (timeouts, etc).
		 */
		if ((error == EINTR || error == ECANCELED) &&
		    (tib->tib_canceled == 0 ||
		    (tib->tib_cantcancel & CANCEL_DISABLED))) {
			_spinlock(&mutex->lock);
			continue;
		}

		/*
		 * The remaining reasons for waking up (normal
		 * wakeup, timeout, and cancellation) all mean that
		 * we won't be staying in the condvar queue and
		 * we'll no longer time out or be cancelable.
		 */
		abstime = NULL;
		LEAVE_CANCEL_POINT_INNER(tib, 0);

		/*
		 * If we're no longer in the condvar's queue then
		 * we're just waiting for mutex ownership.  Need
		 * cond->lock here to prevent race with cond_signal().
		 */
		_spinlock(&cond->lock);
		if (self->blocking_cond == NULL) {
			_spinunlock(&cond->lock);
			_spinlock(&mutex->lock);
			continue;
		}
		assert(self->blocking_cond == cond);

		/* if timeout or canceled, make note of that */
		if (error == EWOULDBLOCK)
			rv = ETIMEDOUT;
		else if (error == EINTR)
			canceled = 1;

		/* transfer between the queues */
		TAILQ_REMOVE(&cond->waiters, self, waiting);
		assert(mutex == cond->mutex);
		if (TAILQ_EMPTY(&cond->waiters))
			cond->mutex = NULL;
		self->blocking_cond = NULL;
		_spinunlock(&cond->lock);
		_spinlock(&mutex->lock);

		/* mutex unlocked right now? */
		if (mutex->owner == NULL &&
		    TAILQ_EMPTY(&mutex->lockers)) {
			assert(mutex->count == 0);
			mutex->owner = self;
			break;
		}
		TAILQ_INSERT_TAIL(&mutex->lockers, self, waiting);
	}

	/* restore the mutex's count */
	mutex->count = mutex_count;
	_spinunlock(&mutex->lock);

	LEAVE_CANCEL_POINT_INNER(tib, canceled);

	return (rv);
}

int
pthread_cond_wait(pthread_cond_t *condp, pthread_mutex_t *mutexp)
{
	pthread_cond_t cond;
	struct pthread_mutex *mutex = (struct pthread_mutex *)*mutexp;
	struct tib *tib = TIB_GET();
	pthread_t self = tib->tib_thread;
	pthread_t next;
	int mutex_count;
	int canceled = 0;
	int error;
	PREP_CANCEL_POINT(tib);

	if (!*condp)
		if ((error = pthread_cond_init(condp, NULL)))
			return (error);
	cond = *condp;
	_rthread_debug(5, "%p: cond_wait %p,%p\n", (void *)self,
	    (void *)cond, (void *)mutex);

	if (mutex == NULL)
#if PTHREAD_MUTEX_DEFAULT == PTHREAD_MUTEX_ERRORCHECK
		return (EPERM);
#else
		abort();
#endif

	if (mutex->owner != self) {
		if (mutex->type == PTHREAD_MUTEX_ERRORCHECK)
			return (EPERM);
		else
			abort();
	}

	ENTER_DELAYED_CANCEL_POINT(tib, self);

	_spinlock(&cond->lock);

	/* mark the condvar as being associated with this mutex */
	if (cond->mutex == NULL) {
		cond->mutex = mutex;
		assert(TAILQ_EMPTY(&cond->waiters));
	} else if (cond->mutex != mutex) {
		assert(cond->mutex == mutex);
		_spinunlock(&cond->lock);
		LEAVE_CANCEL_POINT_INNER(tib, 1);
		return (EINVAL);
	} else
		assert(! TAILQ_EMPTY(&cond->waiters));

	/* snag the count in case this is a recursive mutex */
	mutex_count = mutex->count;

	/* transfer from the mutex queue to the condvar queue */
	_spinlock(&mutex->lock);
	self->blocking_cond = cond;
	TAILQ_INSERT_TAIL(&cond->waiters, self, waiting);
	_spinunlock(&cond->lock);

	/* wake the next guy blocked on the mutex */
	mutex->count = 0;
	mutex->owner = next = TAILQ_FIRST(&mutex->lockers);
	if (next != NULL) {
		TAILQ_REMOVE(&mutex->lockers, next, waiting);
		__thrwakeup(next, 1);
	}

	/* wait until we're the owner of the mutex again */
	while (mutex->owner != self) {
		error = __thrsleep(self, 0, NULL, &mutex->lock,
		    &self->delayed_cancel);

		/*
		 * If we took a normal signal (not from
		 * cancellation) then we should just go back to
		 * sleep without changing state (timeouts, etc).
		 */
		if ((error == EINTR || error == ECANCELED) &&
		    (tib->tib_canceled == 0 ||
		    (tib->tib_cantcancel & CANCEL_DISABLED))) {
			_spinlock(&mutex->lock);
			continue;
		}

		/*
		 * The remaining reasons for waking up (normal
		 * wakeup and cancellation) all mean that we won't
		 * be staying in the condvar queue and we'll no
		 * longer be cancelable.
		 */
		LEAVE_CANCEL_POINT_INNER(tib, 0);

		/*
		 * If we're no longer in the condvar's queue then
		 * we're just waiting for mutex ownership.  Need
		 * cond->lock here to prevent race with cond_signal().
		 */
		_spinlock(&cond->lock);
		if (self->blocking_cond == NULL) {
			_spinunlock(&cond->lock);
			_spinlock(&mutex->lock);
			continue;
		}
		assert(self->blocking_cond == cond);

		/* if canceled, make note of that */
		if (error == EINTR)
			canceled = 1;

		/* transfer between the queues */
		TAILQ_REMOVE(&cond->waiters, self, waiting);
		assert(mutex == cond->mutex);
		if (TAILQ_EMPTY(&cond->waiters))
			cond->mutex = NULL;
		self->blocking_cond = NULL;
		_spinunlock(&cond->lock);
		_spinlock(&mutex->lock);

		/* mutex unlocked right now? */
		if (mutex->owner == NULL &&
		    TAILQ_EMPTY(&mutex->lockers)) {
			assert(mutex->count == 0);
			mutex->owner = self;
			break;
		}
		TAILQ_INSERT_TAIL(&mutex->lockers, self, waiting);
	}

	/* restore the mutex's count */
	mutex->count = mutex_count;
	_spinunlock(&mutex->lock);

	LEAVE_CANCEL_POINT_INNER(tib, canceled);

	return (0);
}


int
pthread_cond_signal(pthread_cond_t *condp)
{
	pthread_cond_t cond;
	struct pthread_mutex *mutex;
	pthread_t thread;
	int wakeup;

	/* uninitialized?  Then there's obviously no one waiting! */
	if (!*condp)
		return 0;

	cond = *condp;
	_rthread_debug(5, "%p: cond_signal %p,%p\n", (void *)pthread_self(),
	    (void *)cond, (void *)cond->mutex);
	_spinlock(&cond->lock);
	thread = TAILQ_FIRST(&cond->waiters);
	if (thread == NULL) {
		assert(cond->mutex == NULL);
		_spinunlock(&cond->lock);
		return (0);
	}

	assert(thread->blocking_cond == cond);
	TAILQ_REMOVE(&cond->waiters, thread, waiting);
	thread->blocking_cond = NULL;

	mutex = cond->mutex;
	assert(mutex != NULL);
	if (TAILQ_EMPTY(&cond->waiters))
		cond->mutex = NULL;

	/* link locks to prevent race with timedwait */
	_spinlock(&mutex->lock);
	_spinunlock(&cond->lock);

	wakeup = mutex->owner == NULL && TAILQ_EMPTY(&mutex->lockers);
	if (wakeup)
		mutex->owner = thread;
	else
		TAILQ_INSERT_TAIL(&mutex->lockers, thread, waiting);
	_spinunlock(&mutex->lock);
	if (wakeup)
		__thrwakeup(thread, 1);

	return (0);
}

int
pthread_cond_broadcast(pthread_cond_t *condp)
{
	pthread_cond_t cond;
	struct pthread_mutex *mutex;
	pthread_t thread;
	pthread_t p;
	int wakeup;

	/* uninitialized?  Then there's obviously no one waiting! */
	if (!*condp)
		return 0;

	cond = *condp;
	_rthread_debug(5, "%p: cond_broadcast %p,%p\n", (void *)pthread_self(),
	    (void *)cond, (void *)cond->mutex);
	_spinlock(&cond->lock);
	thread = TAILQ_FIRST(&cond->waiters);
	if (thread == NULL) {
		assert(cond->mutex == NULL);
		_spinunlock(&cond->lock);
		return (0);
	}

	mutex = cond->mutex;
	assert(mutex != NULL);

	/* walk the list, clearing the "blocked on condvar" pointer */
	p = thread;
	do
		p->blocking_cond = NULL;
	while ((p = TAILQ_NEXT(p, waiting)) != NULL);

	/*
	 * We want to transfer all the threads from the condvar's list
	 * to the mutex's list.  The TAILQ_* macros don't let us do that
	 * efficiently, so this is direct list surgery.  Pay attention!
	 */

	/* 1) attach the first thread to the end of the mutex's list */
	_spinlock(&mutex->lock);
	wakeup = mutex->owner == NULL && TAILQ_EMPTY(&mutex->lockers);
	thread->waiting.tqe_prev = mutex->lockers.tqh_last;
	*(mutex->lockers.tqh_last) = thread;

	/* 2) fix up the end pointer for the mutex's list */
	mutex->lockers.tqh_last = cond->waiters.tqh_last;

	if (wakeup) {
		TAILQ_REMOVE(&mutex->lockers, thread, waiting);
		mutex->owner = thread;
		_spinunlock(&mutex->lock);
		__thrwakeup(thread, 1);
	} else
		_spinunlock(&mutex->lock);

	/* 3) reset the condvar's list and mutex pointer */
	TAILQ_INIT(&cond->waiters);
	assert(cond->mutex != NULL);
	cond->mutex = NULL;
	_spinunlock(&cond->lock);

	return (0);
}
IABSD.fr/src/lib/libc/thread/rthread_sync.c

Commit

IABSD.fr/src /lib/libc/thread/rthread_sync.c
