path: root/lib/libpthread/thread/thr_mutex.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 REGENTS 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 <stdlib.h>
#include <errno.h>
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"

int
pthread_mutex_init(pthread_mutex_t * mutex,
		   const pthread_mutexattr_t * mutex_attr)
{
	enum pthread_mutextype type;
	int             ret = 0;
	int             status;

	/* Check if the mutex attributes specify some mutex other than fast: */
	if (mutex_attr != NULL && mutex_attr->m_type != MUTEX_TYPE_FAST) {
		/* Check if the mutex type is out of range: */
		if (mutex_attr->m_type >= MUTEX_TYPE_MAX) {
			/* Return an invalid argument error: */
			_thread_seterrno(_thread_run, EINVAL);
			ret = -1;
		} else {
			/* Use the requested mutex type: */
			type = mutex_attr->m_type;
		}
	} else {
		/* Default to a fast mutex: */
		type = MUTEX_TYPE_FAST;
	}

	/* Check no errors so far: */
	if (ret == 0) {
		/* Reset the mutex flags: */
		mutex->m_flags = 0;

		/* Block signals: */
		_thread_kern_sig_block(&status);

		/* Process according to mutex type: */
		switch (type) {
			/* Fast mutex: */
		case MUTEX_TYPE_FAST:
			/* Nothing to do here. */
			break;

			/* Counting mutex: */
		case MUTEX_TYPE_COUNTING_FAST:
			/* Reset the mutex count: */
			mutex->m_data.m_count = 0;
			break;

			/* Trap invalid mutex types: */
		default:
			/* Return an invalid argument error: */
			_thread_seterrno(_thread_run, EINVAL);
			ret = -1;
			break;
		}

		/* Initialise the rest of the mutex: */
		_thread_queue_init(&mutex->m_queue);
		mutex->m_flags |= MUTEX_FLAGS_INITED;
		mutex->m_owner = NULL;
		mutex->m_type = type;

		/* Unblock signals: */
		_thread_kern_sig_unblock(status);
	}
	/* Return the completion status: */
	return (ret);
}

int
pthread_mutex_destroy(pthread_mutex_t * mutex)
{
	int             ret = 0;
	int             status;

	/* Block signals: */
	_thread_kern_sig_block(&status);

	/* Process according to mutex type: */
	switch (mutex->m_type) {
		/* Fast mutex: */
	case MUTEX_TYPE_FAST:
		/* Nothing to do here. */
		break;

		/* Counting mutex: */
	case MUTEX_TYPE_COUNTING_FAST:
		/* Reset the mutex count: */
		mutex->m_data.m_count = 0;
		break;

		/* Trap undefined mutex types: */
	default:
		/* Return an invalid argument error: */
		_thread_seterrno(_thread_run, EINVAL);
		ret = -1;
		break;
	}

	/* Clean up the mutex in case that others want to use it: */
	_thread_queue_init(&mutex->m_queue);
	mutex->m_owner = NULL;
	mutex->m_flags = 0;

	/* Unblock signals: */
	_thread_kern_sig_unblock(status);

	/* Return the completion status: */
	return (ret);
}

int
pthread_mutex_trylock(pthread_mutex_t * mutex)
{
	int             ret = 0;
	int             status;

	/* Block signals: */
	_thread_kern_sig_block(&status);

	/* Process according to mutex type: */
	switch (mutex->m_type) {
		/* Fast mutex: */
	case MUTEX_TYPE_FAST:
		/* Check if this mutex is not locked: */
		if (mutex->m_owner == NULL) {
			/* Lock the mutex for the running thread: */
			mutex->m_owner = _thread_run;
		} else {
			/* Return a busy error: */
			_thread_seterrno(_thread_run, EBUSY);
			ret = -1;
		}
		break;

		/* Counting mutex: */
	case MUTEX_TYPE_COUNTING_FAST:
		/* Check if this mutex is locked: */
		if (mutex->m_owner != NULL) {
			/*
			 * Check if the mutex is locked by the running
			 * thread: 
			 */
			if (mutex->m_owner == _thread_run) {
				/* Increment the lock count: */
				mutex->m_data.m_count++;
			} else {
				/* Return a busy error: */
				_thread_seterrno(_thread_run, EBUSY);
				ret = -1;
			}
		} else {
			/* Lock the mutex for the running thread: */
			mutex->m_owner = _thread_run;
		}
		break;

		/* Trap invalid mutex types: */
	default:
		/* Return an invalid argument error: */
		_thread_seterrno(_thread_run, EINVAL);
		ret = -1;
		break;
	}

	/* Unblock signals: */
	_thread_kern_sig_unblock(status);

	/* Return the completion status: */
	return (ret);
}

int
pthread_mutex_lock(pthread_mutex_t * mutex)
{
	int             ret = 0;
	int             status;

	/* Block signals: */
	_thread_kern_sig_block(&status);

	/* Process according to mutex type: */
	switch (mutex->m_type) {
		/* Fast mutexes do not check for any error conditions: */
	case MUTEX_TYPE_FAST:
		/*
		 * Enter a loop to wait for the mutex to be locked by the
		 * current thread: 
		 */
		while (mutex->m_owner != _thread_run) {
			/* Check if the mutex is not locked: */
			if (mutex->m_owner == NULL) {
				/* Lock the mutex for this thread: */
				mutex->m_owner = _thread_run;
			} else {
				/*
				 * Join the queue of threads waiting to lock
				 * the mutex: 
				 */
				_thread_queue_enq(&mutex->m_queue, _thread_run);

				/* Block signals: */
				_thread_kern_sched_state(PS_MUTEX_WAIT, __FILE__, __LINE__);

				/* Block signals: */
				_thread_kern_sig_block(NULL);
			}
		}
		break;

		/* Counting mutex: */
	case MUTEX_TYPE_COUNTING_FAST:
		/*
		 * Enter a loop to wait for the mutex to be locked by the
		 * current thread: 
		 */
		while (mutex->m_owner != _thread_run) {
			/* Check if the mutex is not locked: */
			if (mutex->m_owner == NULL) {
				/* Lock the mutex for this thread: */
				mutex->m_owner = _thread_run;

				/* Reset the lock count for this mutex: */
				mutex->m_data.m_count = 0;
			} else {
				/*
				 * Join the queue of threads waiting to lock
				 * the mutex: 
				 */
				_thread_queue_enq(&mutex->m_queue, _thread_run);

				/* Block signals: */
				_thread_kern_sched_state(PS_MUTEX_WAIT, __FILE__, __LINE__);

				/* Block signals: */
				_thread_kern_sig_block(NULL);
			}
		}

		/* Increment the lock count for this mutex: */
		mutex->m_data.m_count++;
		break;

		/* Trap invalid mutex types: */
	default:
		/* Return an invalid argument error: */
		_thread_seterrno(_thread_run, EINVAL);
		ret = -1;
		break;
	}

	/* Unblock signals: */
	_thread_kern_sig_unblock(status);

	/* Return the completion status: */
	return (ret);
}

int
pthread_mutex_unlock(pthread_mutex_t * mutex)
{
	int             ret = 0;
	int             status;

	/* Block signals: */
	_thread_kern_sig_block(&status);

	/* Process according to mutex type: */
	switch (mutex->m_type) {
		/* Fast mutexes do not check for any error conditions: */
	case MUTEX_TYPE_FAST:
		/* Check if the running thread is not the owner of the mutex: */
		if (mutex->m_owner != _thread_run) {
			/* Return an invalid argument error: */
			_thread_seterrno(_thread_run, EINVAL);
			ret = -1;
		}
		/*
		 * Get the next thread from the queue of threads waiting on
		 * the mutex: 
		 */
		else if ((mutex->m_owner = _thread_queue_deq(&mutex->m_queue)) != NULL) {
			/* Allow the new owner of the mutex to run: */
			mutex->m_owner->state = PS_RUNNING;
		}
		break;

		/* Counting mutex: */
	case MUTEX_TYPE_COUNTING_FAST:
		/* Check if the running thread is not the owner of the mutex: */
		if (mutex->m_owner != _thread_run) {
			/* Return an invalid argument error: */
			_thread_seterrno(_thread_run, EINVAL);
			ret = -1;
		}
		/* Check if there are still counts: */
		else if (mutex->m_data.m_count) {
			/* Decrement the count: */
			mutex->m_data.m_count--;
		}
		/*
		 * Get the next thread from the queue of threads waiting on
		 * the mutex: 
		 */
		else if ((mutex->m_owner = _thread_queue_deq(&mutex->m_queue)) != NULL) {
			/* Allow the new owner of the mutex to run: */
			mutex->m_owner->state = PS_RUNNING;
		}
		break;

		/* Trap invalid mutex types: */
	default:
		/* Return an invalid argument error: */
		_thread_seterrno(_thread_run, EINVAL);
		ret = -1;
		break;
	}

	/* Unblock signals: */
	_thread_kern_sig_unblock(status);

	/* Return the completion status: */
	return (ret);
}
#endif