path: root/lib/libc_r/uthread/uthread_fd.c

/*	$OpenBSD: uthread_fd.c,v 1.11 2002/10/30 20:05:11 marc Exp $	*/
/*
 * Copyright (c) 1995-1998 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: uthread_fd.c,v 1.13 1999/08/28 00:03:31 peter Exp $
 *
 */
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"

/* Static variables: */
static	spinlock_t	fd_table_lock	= _SPINLOCK_INITIALIZER;

/*
 * Initialize the fd_table entry for the given fd.
 *
 * This function *must* return -1 and set the thread specific errno
 * as a system call. This is because the error return from this
 * function is propagated directly back from thread-wrapped system
 * calls.
 */
int
_thread_fd_table_init(int fd)
{
	int	ret = 0;
	struct fd_table_entry *entry;
	int	saved_errno;

	if (fd < 0 || fd >= _thread_dtablesize) {
		/*
		 * file descriptor is out of range, Return a bad file
		 * descriptor error:
		 */ 
		errno = EBADF;
		ret = -1;
	} else if (_thread_fd_table[fd] == NULL) {
		/* First time for this fd, build an entry */
		entry = (struct fd_table_entry *)
		        malloc(sizeof(struct fd_table_entry));
		if (entry == NULL) {
			errno = ENOMEM;
			ret = -1;
		} else {
			/* Initialise the file locks: */
			_SPINLOCK_INIT(&entry->lock);
			entry->r_owner = NULL;
			entry->w_owner = NULL;
			entry->r_fname = NULL;
			entry->w_fname = NULL;
			entry->r_lineno = 0;
			entry->w_lineno = 0;
			entry->r_lockcount = 0;
			entry->w_lockcount = 0;

			/* Initialise the read/write queues: */
			TAILQ_INIT(&entry->r_queue);
			TAILQ_INIT(&entry->w_queue);

			/* Get the flags for the file: */
			entry->flags = _thread_sys_fcntl(fd, F_GETFL, 0);
			if (entry->flags == -1)
				/* use the errno fcntl returned */
				ret = -1;
			else {
				/*
				 * Make the file descriptor non-blocking.
				 * This might fail if the device driver does
				 * not support non-blocking calls, or if the
				 * driver is naturally non-blocking.
				 */
				saved_errno = errno;
				_thread_sys_fcntl(fd, F_SETFL,
						  entry->flags | O_NONBLOCK);
				errno = saved_errno;

				/* Lock the file descriptor table: */
				_SPINLOCK(&fd_table_lock);

				/*
				 * Check if another thread allocated the
				 * file descriptor entry while this thread
				 * was doing the same thing. The table wasn't
				 * kept locked during this operation because
				 * it has the potential to recurse.
				 */
				if (_thread_fd_table[fd] == NULL) {
					/* This thread wins: */
					_thread_fd_table[fd] = entry;
					entry = NULL;
				}

				/* Unlock the file descriptor table: */
				_SPINUNLOCK(&fd_table_lock);
			}

			/*
			 * If there was an error in getting the flags for
			 * the file or if another thread initialized the
			 * table entry throw this entry away.
			 */
			if (entry != NULL)
				free(entry);
		}
	}

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

/*
 * Unlock the fd table entry for a given thread, fd, and lock type.
 */
void
_thread_fd_unlock_thread(struct pthread	*thread, int fd, int lock_type,
			 char *fname, int lineno)
{
	struct fd_table_entry *entry;
	int	ret;

	/*
	 * Check that the file descriptor table is initialised for this
	 * entry: 
	 */
	ret = _thread_fd_table_init(fd);
	if (ret == 0) {
		entry = _thread_fd_table[fd];

		/*
		 * Defer signals to protect the scheduling queues from
		 * access by the signal handler:
		 */
		_thread_kern_sig_defer();

		/*
		 * Lock the file descriptor table entry to prevent
		 * other threads for clashing with the current
		 * thread's accesses:
		 */
		if (fname)
			_spinlock_debug(&entry->lock, fname, lineno);
		else
			_SPINLOCK(&entry->lock);

		/* Check if the running thread owns the read lock: */
		if (entry->r_owner == thread &&
		    (lock_type == FD_READ || lock_type == FD_RDWR)) {
			/*
			 * Decrement the read lock count for the
			 * running thread: 
			 */
			entry->r_lockcount--;
			if (entry->r_lockcount == 0) {
				/*
				 * no read locks, dequeue any threads
				 * waiting for a read lock
				 */
				entry->r_owner = TAILQ_FIRST(&entry->r_queue);
				if (entry->r_owner != NULL) {
					TAILQ_REMOVE(&entry->r_queue,
						     entry->r_owner, qe);

					/*
					 * Set the state of the new owner of
					 * the thread to running:  
					 */
					PTHREAD_NEW_STATE(entry->r_owner,
							  PS_RUNNING);

					/*
					 * Reset the number of read locks.
					 * This will be incremented by the new
					 * owner of the lock when it sees that
					 *it has the lock.
					 */
					entry->r_lockcount = 0;
				}
			}

		}
		/* Check if the running thread owns the write lock: */
		if (entry->w_owner == thread &&
		    (lock_type == FD_WRITE || lock_type == FD_RDWR)) {
			/*
			 * Decrement the write lock count for the
			 * running thread: 
			 */
			entry->w_lockcount--;
			if (entry->w_lockcount == 0) {
				/*
				 * no write locks, dequeue any threads
				 * waiting on a write lock.
				 */
				entry->w_owner = TAILQ_FIRST(&entry->w_queue);
				if (entry->w_owner != NULL) {
					/* Remove this thread from the queue: */
					TAILQ_REMOVE(&entry->w_queue,
						     entry->w_owner, qe);

					/*
					 * Set the state of the new owner of
					 * the thread to running: 
					 */
					PTHREAD_NEW_STATE(entry->w_owner,
							  PS_RUNNING);

					/*
					 * Reset the number of write locks.
					 * This will be incremented by the
					 * new owner of the lock when it  
					 * sees that it has the lock.
					 */
					entry->w_lockcount = 0;
				}
			}
		}

		/* Unlock the file descriptor table entry: */
		_SPINUNLOCK(&entry->lock);

		/*
		 * Undefer and handle pending signals, yielding if
		 * necessary:
		 */
		_thread_kern_sig_undefer();
	}

	/* Nothing to return. */
	return;
}

/*
 * Unlock an fd table entry for the given fd and lock type.  Save
 * fname and lineno (debug variables).
 */
void
_thread_fd_unlock_debug(int fd, int lock_type, char *fname, int lineno)
{
	struct pthread	*curthread = _get_curthread();
	return (_thread_fd_unlock_thread(curthread, fd, lock_type,
					 fname, lineno));
}

/*
 * Unlock an fd table entry for the given fd and lock type (read,
 * write, or read-write).
 */
void
_thread_fd_unlock(int fd, int lock_type)
{
	struct pthread	*curthread = _get_curthread();
	return (_thread_fd_unlock_thread(curthread, fd, lock_type, NULL, 0));
}

/*
 * Unlock all fd table entries owned by the given thread
 */
void
_thread_fd_unlock_owned(pthread_t pthread)
{
	struct pthread	*saved_thread = _get_curthread();
	struct fd_table_entry *entry;
	int do_unlock;
	int fd;

	for (fd = 0; fd < _thread_dtablesize; fd++) {
		entry = _thread_fd_table[fd];
		if (entry) {
			_SPINLOCK(&entry->lock);
			do_unlock = 0;
			/* force an unlock regardless of the recursion level */
			if (entry->r_owner == pthread) {
				entry->r_lockcount = 1;
				do_unlock++;
			}
			if (entry->w_owner == pthread) {
				entry->w_lockcount = 1;
				do_unlock++;
			}
			_SPINUNLOCK(&entry->lock);
			if (do_unlock)
				_thread_fd_unlock_thread(pthread, fd, FD_RDWR,
							 __FILE__, __LINE__);
		}
	}
}

/*
 * Lock an fd table entry for the given fd and lock type.  Save
 * fname and lineno (debug variables).  The debug variables may be
 * null when called by the non-debug version of the function.
 */
int
_thread_fd_lock_debug(int fd, int lock_type, struct timespec * timeout,
		      char *fname, int lineno)
{
	struct pthread	*curthread = _get_curthread();
	struct fd_table_entry *entry;
	int	ret;

	/*
	 * Check that the file descriptor table is initialised for this
	 * entry: 
	 */
	ret = _thread_fd_table_init(fd);
	if (ret == 0) {
		entry = _thread_fd_table[fd];

		/*
		 * Lock the file descriptor table entry to prevent
		 * other threads for clashing with the current
		 * thread's accesses:
		 */
		if (fname)
			_spinlock_debug(&entry->lock, fname, lineno);
		else
			_SPINLOCK(&entry->lock);

		/* Handle read locks */
		if (lock_type == FD_READ || lock_type == FD_RDWR) {
			/*
			 * Enter a loop to wait for the file descriptor to be
			 * locked    for read for the current thread: 
			 */
			while (entry->r_owner != curthread) {
				/*
				 * Check if the file descriptor is locked by
				 * another thread: 
				 */
				if (entry->r_owner != NULL) {
					/*
					 * Another thread has locked the file
					 * descriptor for read, so join the
					 * queue of threads waiting for a  
					 * read lock on this file descriptor: 
					 */
					TAILQ_INSERT_TAIL(&entry->r_queue,
							  curthread, qe);

					/*
					 * Save the file descriptor details
					 * in the thread structure for the
					 * running thread: 
					 */
					curthread->data.fd.fd = fd;
					curthread->data.fd.branch = lineno;
					curthread->data.fd.fname = fname;

					/* Set the timeout: */
					_thread_kern_set_timeout(timeout);

					/*
					 * Unlock the file descriptor
					 * table entry:
					 */
					_SPINUNLOCK(&entry->lock);

					/*
					 * Schedule this thread to wait on
					 * the read lock. It will only be
					 * woken when it becomes the next in
					 * the   queue and is granted access
					 * to the lock by the thread that is
					 * unlocking the file descriptor.
					 */
					_thread_kern_sched_state(PS_FDLR_WAIT,
								 __FILE__,
								 __LINE__);

					/*
					 * Lock the file descriptor
					 * table entry again:
					 */
					_SPINLOCK(&entry->lock);

				} else {
					/*
					 * The running thread now owns the
					 * read lock on this file descriptor: 
					 */
					entry->r_owner = curthread;

					/*
					 * Reset the number of read locks for
					 * this file descriptor: 
					 */
					entry->r_lockcount = 0;
					entry->r_fname = fname;
					entry->r_lineno = lineno;
				}
			}

			/* Increment the read lock count: */
			entry->r_lockcount++;
		}

		/* Handle write locks */
		if (lock_type == FD_WRITE || lock_type == FD_RDWR) {
			/*
			 * Enter a loop to wait for the file descriptor to be
			 * locked for write for the current thread: 
			 */
			while (entry->w_owner != curthread) {
				/*
				 * Check if the file descriptor is locked by
				 * another thread: 
				 */
				if (entry->w_owner != NULL) {
					/*
					 * Another thread has locked the file
					 * descriptor for write, so join the
					 * queue of threads waiting for a 
					 * write lock on this file
					 * descriptor: 
					 */
					TAILQ_INSERT_TAIL(&entry->w_queue,
							  curthread, qe);

					/*
					 * Save the file descriptor details
					 * in the thread structure for the
					 * running thread: 
					 */
					curthread->data.fd.fd = fd;
					curthread->data.fd.branch = lineno;
					curthread->data.fd.fname = fname;

					/* Set the timeout: */
					_thread_kern_set_timeout(timeout);

					/*
					 * Unlock the file descriptor
					 * table entry:
					 */
					_SPINUNLOCK(&entry->lock);

					/*
					 * Schedule this thread to wait on
					 * the write lock. It will only be
					 * woken when it becomes the next in
					 * the queue and is granted access to
					 * the lock by the thread that is
					 * unlocking the file descriptor.
					 */
					_thread_kern_sched_state(PS_FDLW_WAIT,
								 __FILE__,
								 __LINE__);

					/*
					 * Lock the file descriptor
					 * table entry again:
					 */
					_SPINLOCK(&entry->lock);
				} else {
					/*
					 * The running thread now owns the
					 * write lock on this file descriptor: 
					 */
					entry->w_owner = curthread;

					/*
					 * Reset the number of write locks
					 * for this file descriptor: 
					 */
					entry->w_lockcount = 0;
					entry->w_fname = fname;
					entry->w_lineno = lineno;
				}
			}

			/* Increment the write lock count: */
			entry->w_lockcount++;
		}

		/* Unlock the file descriptor table entry: */
		_SPINUNLOCK(&entry->lock);
	}

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

/*
 * Non-debug version of fd locking.  Just call the debug version
 * passing a null file and line
 */
int
_thread_fd_lock(int fd, int lock_type, struct timespec * timeout)
{
	return (_thread_fd_lock_debug(fd, lock_type, timeout, NULL, 0));
}

#endif