745a12fc30
which don't provide a non-blocking interface. This is a short term "fix" which changes a half-lose to a half-win. The thread that accesses a device that does not provide a non-blocking interface will block for its time slice. A medium term solution would be to use rfork. A long-term solution would be some sort of kernel thread/SMP implementation.
406 lines
11 KiB
C
406 lines
11 KiB
C
/*
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* Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by John Birrell.
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* 4. Neither the name of the author nor the names of any co-contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $Id$
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*
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*/
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#include <errno.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#ifdef _THREAD_SAFE
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#include <pthread.h>
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#include "pthread_private.h"
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int
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_thread_fd_table_init(int fd)
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{
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int ret = 0;
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int status;
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/* Block signals: */
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_thread_kern_sig_block(&status);
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/* Check if the file descriptor is out of range: */
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if (fd < 0 || fd >= _thread_dtablesize)
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/* Return a bad file descriptor error: */
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ret = EBADF;
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/*
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* Check if memory has already been allocated for this file
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* descriptor:
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*/
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else if (_thread_fd_table[fd] != NULL) {
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/* Memory has already been allocated. */
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}
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/* Allocate memory for the file descriptor table entry: */
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else if ((_thread_fd_table[fd] = (struct fd_table_entry *)
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malloc(sizeof(struct fd_table_entry))) == NULL)
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/* Return a bad file descriptor error: */
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ret = EBADF;
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else {
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/* Assume that the operation will succeed: */
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ret = 0;
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/* Initialise the file locks: */
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_thread_fd_table[fd]->r_owner = NULL;
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_thread_fd_table[fd]->w_owner = NULL;
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_thread_fd_table[fd]->r_fname = NULL;
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_thread_fd_table[fd]->w_fname = NULL;
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_thread_fd_table[fd]->r_lineno = 0;;
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_thread_fd_table[fd]->w_lineno = 0;;
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_thread_fd_table[fd]->r_lockcount = 0;;
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_thread_fd_table[fd]->w_lockcount = 0;;
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/* Initialise the read/write queues: */
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_thread_queue_init(&_thread_fd_table[fd]->r_queue);
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_thread_queue_init(&_thread_fd_table[fd]->w_queue);
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/* Get the flags for the file: */
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if (fd >= 3 && (_thread_fd_table[fd]->flags =
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_thread_sys_fcntl(fd, F_GETFL, 0)) == -1)
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ret = errno;
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else {
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/* Check if a stdio descriptor: */
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if (fd < 3)
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/*
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* Use the stdio flags read by
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* _pthread_init() to avoid
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* mistaking the non-blocking
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* flag that, when set on one
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* stdio fd, is set on all stdio
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* fds.
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*/
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_thread_fd_table[fd]->flags =
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_pthread_stdio_flags[fd];
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/* Make the file descriptor non-blocking: */
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if (_thread_sys_fcntl(fd, F_SETFL,
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_thread_fd_table[fd]->flags | O_NONBLOCK) == -1) {
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/*
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* Some devices don't support
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* non-blocking calls (sigh):
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*/
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if (errno != ENODEV)
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ret = errno;
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}
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}
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/* Check if one of the fcntl calls failed: */
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if (ret != 0) {
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/* Free the file descriptor table entry: */
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free(_thread_fd_table[fd]);
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_thread_fd_table[fd] = NULL;
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}
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}
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/* Unblock signals: */
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_thread_kern_sig_unblock(status);
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/* Return the completion status: */
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return (ret);
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}
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void
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_thread_fd_unlock(int fd, int lock_type)
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{
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int ret;
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int status;
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/* Block signals while the file descriptor lock is tested: */
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_thread_kern_sig_block(&status);
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/*
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* Check that the file descriptor table is initialised for this
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* entry:
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*/
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if ((ret = _thread_fd_table_init(fd)) != 0) {
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} else {
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/* Check if the running thread owns the read lock: */
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if (_thread_fd_table[fd]->r_owner == _thread_run) {
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/* Check the file descriptor and lock types: */
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if (lock_type == FD_READ || lock_type == FD_RDWR) {
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/*
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* Decrement the read lock count for the
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* running thread:
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*/
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_thread_fd_table[fd]->r_lockcount--;
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/*
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* Check if the running thread still has read
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* locks on this file descriptor:
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*/
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if (_thread_fd_table[fd]->r_lockcount != 0) {
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}
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/*
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* Get the next thread in the queue for a
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* read lock on this file descriptor:
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*/
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else if ((_thread_fd_table[fd]->r_owner = _thread_queue_deq(&_thread_fd_table[fd]->r_queue)) == NULL) {
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} else {
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/*
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* Set the state of the new owner of
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* the thread to running:
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*/
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PTHREAD_NEW_STATE(_thread_fd_table[fd]->r_owner,PS_RUNNING);
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/*
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* Reset the number of read locks.
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* This will be incremented by the
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* new owner of the lock when it sees
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* that it has the lock.
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*/
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_thread_fd_table[fd]->r_lockcount = 0;
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}
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}
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}
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/* Check if the running thread owns the write lock: */
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if (_thread_fd_table[fd]->w_owner == _thread_run) {
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/* Check the file descriptor and lock types: */
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if (lock_type == FD_WRITE || lock_type == FD_RDWR) {
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/*
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* Decrement the write lock count for the
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* running thread:
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*/
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_thread_fd_table[fd]->w_lockcount--;
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/*
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* Check if the running thread still has
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* write locks on this file descriptor:
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*/
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if (_thread_fd_table[fd]->w_lockcount != 0) {
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}
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/*
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* Get the next thread in the queue for a
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* write lock on this file descriptor:
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*/
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else if ((_thread_fd_table[fd]->w_owner = _thread_queue_deq(&_thread_fd_table[fd]->w_queue)) == NULL) {
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} else {
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/*
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* Set the state of the new owner of
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* the thread to running:
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*/
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PTHREAD_NEW_STATE(_thread_fd_table[fd]->w_owner,PS_RUNNING);
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/*
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* Reset the number of write locks.
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* This will be incremented by the
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* new owner of the lock when it
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* sees that it has the lock.
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*/
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_thread_fd_table[fd]->w_lockcount = 0;
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}
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}
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}
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}
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/* Unblock signals again: */
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_thread_kern_sig_unblock(status);
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/* Nothing to return. */
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return;
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}
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int
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_thread_fd_lock(int fd, int lock_type, struct timespec * timeout,
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char *fname, int lineno)
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{
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int ret;
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int status;
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/* Block signals while the file descriptor lock is tested: */
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_thread_kern_sig_block(&status);
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/*
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* Check that the file descriptor table is initialised for this
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* entry:
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*/
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if ((ret = _thread_fd_table_init(fd)) != 0) {
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} else {
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/* Check the file descriptor and lock types: */
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if (lock_type == FD_READ || lock_type == FD_RDWR) {
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/*
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* Enter a loop to wait for the file descriptor to be
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* locked for read for the current thread:
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*/
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while (_thread_fd_table[fd]->r_owner != _thread_run) {
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/*
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* Check if the file descriptor is locked by
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* another thread:
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*/
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if (_thread_fd_table[fd]->r_owner != NULL) {
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/*
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* Another thread has locked the file
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* descriptor for read, so join the
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* queue of threads waiting for a
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* read lock on this file descriptor:
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*/
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_thread_queue_enq(&_thread_fd_table[fd]->r_queue, _thread_run);
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/*
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* Save the file descriptor details
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* in the thread structure for the
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* running thread:
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*/
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_thread_run->data.fd.fd = fd;
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_thread_run->data.fd.branch = lineno;
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_thread_run->data.fd.fname = fname;
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/* Set the timeout: */
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_thread_kern_set_timeout(timeout);
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/*
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* Schedule this thread to wait on
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* the read lock. It will only be
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* woken when it becomes the next in
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* the queue and is granted access
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* to the lock by the thread
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* that is unlocking the file
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* descriptor.
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*/
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_thread_kern_sched_state(PS_FDLR_WAIT, __FILE__, __LINE__);
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/*
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* Block signals so that the file
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* descriptor lock can again be
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* tested:
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*/
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_thread_kern_sig_block(NULL);
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} else {
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/*
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* The running thread now owns the
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* read lock on this file descriptor:
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*/
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_thread_fd_table[fd]->r_owner = _thread_run;
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/*
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* Reset the number of read locks for
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* this file descriptor:
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*/
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_thread_fd_table[fd]->r_lockcount = 0;
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/*
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* Save the source file details for
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* debugging:
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*/
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_thread_fd_table[fd]->r_fname = fname;
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_thread_fd_table[fd]->r_lineno = lineno;
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}
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}
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/* Increment the read lock count: */
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_thread_fd_table[fd]->r_lockcount++;
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}
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/* Check the file descriptor and lock types: */
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if (lock_type == FD_WRITE || lock_type == FD_RDWR) {
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/*
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* Enter a loop to wait for the file descriptor to be
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* locked for write for the current thread:
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*/
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while (_thread_fd_table[fd]->w_owner != _thread_run) {
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/*
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* Check if the file descriptor is locked by
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* another thread:
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*/
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if (_thread_fd_table[fd]->w_owner != NULL) {
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/*
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* Another thread has locked the file
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* descriptor for write, so join the
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* queue of threads waiting for a
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* write lock on this file
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* descriptor:
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*/
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_thread_queue_enq(&_thread_fd_table[fd]->w_queue, _thread_run);
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/*
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* Save the file descriptor details
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* in the thread structure for the
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* running thread:
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*/
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_thread_run->data.fd.fd = fd;
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_thread_run->data.fd.branch = lineno;
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_thread_run->data.fd.fname = fname;
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/* Set the timeout: */
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_thread_kern_set_timeout(timeout);
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/*
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* Schedule this thread to wait on
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* the write lock. It will only be
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* woken when it becomes the next in
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* the queue and is granted access to
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* the lock by the thread that is
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* unlocking the file descriptor.
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*/
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_thread_kern_sched_state(PS_FDLW_WAIT, __FILE__, __LINE__);
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/*
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* Block signals so that the file
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* descriptor lock can again be
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* tested:
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*/
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_thread_kern_sig_block(NULL);
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} else {
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/*
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* The running thread now owns the
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* write lock on this file
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* descriptor:
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*/
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_thread_fd_table[fd]->w_owner = _thread_run;
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/*
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* Reset the number of write locks
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* for this file descriptor:
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*/
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_thread_fd_table[fd]->w_lockcount = 0;
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/*
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* Save the source file details for
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* debugging:
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*/
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_thread_fd_table[fd]->w_fname = fname;
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_thread_fd_table[fd]->w_lineno = lineno;
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}
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}
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/* Increment the write lock count: */
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_thread_fd_table[fd]->w_lockcount++;
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}
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}
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/* Unblock signals again: */
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_thread_kern_sig_unblock(status);
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/* Return the completion status: */
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return (ret);
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}
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#endif
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