4a027d50c7
for the process, not a separate set for each thread). By default, the process now only has signal handlers installed for SIGVTALRM, SIGINFO and SIGCHLD. The thread kernel signal handler is installed for other signals on demand. This means that SIG_IGN and SIG_DFL processing is now left to the kernel, not the thread kernel. Change the signal dispatch to no longer use a signal thread, and call the signal handler using the stack of the thread that has the signal pending. Change the atomic lock method to use test-and-set asm code with a yield if blocked. This introduces separate locks for each type of object instead of blocking signals to prevent a context switch. It was this blocking of signals that caused the performance degradation the people have noted. This is a *big* change!
435 lines
12 KiB
C
435 lines
12 KiB
C
/*
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* Copyright (c) 1995-1998 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: uthread_fd.c,v 1.5 1998/02/13 01:27:32 julian Exp $
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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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/* Static variables: */
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static long fd_table_lock = 0;
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/*
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* This function *must* return -1 and set the thread specific errno
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* as a system call. This is because the error return from this
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* function is propagated directly back from thread-wrapped system
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* calls.
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*/
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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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/* Lock the file descriptor table: */
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_spinlock(&fd_table_lock);
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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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errno = EBADF;
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ret = -1;
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}
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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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errno = EBADF;
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ret = -1;
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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]->access_lock = 0;
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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 = -1;
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}
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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 = -1;
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}
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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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/* Unlock the file descriptor table: */
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_atomic_unlock(&fd_table_lock);
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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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/*
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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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/*
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* Lock the file descriptor table entry to prevent
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* other threads for clashing with the current
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* thread's accesses:
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*/
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_spinlock(&_thread_fd_table[fd]->access_lock);
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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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/* Unlock the file descriptor table entry: */
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_atomic_unlock(&_thread_fd_table[fd]->access_lock);
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}
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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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/*
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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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/*
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* Lock the file descriptor table entry to prevent
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* other threads for clashing with the current
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* thread's accesses:
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*/
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_spinlock(&_thread_fd_table[fd]->access_lock);
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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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* Unlock the file descriptor
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* table entry:
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*/
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_atomic_unlock(&_thread_fd_table[fd]->access_lock);
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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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* Lock the file descriptor
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* table entry again:
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*/
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_spinlock(&_thread_fd_table[fd]->access_lock);
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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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* Unlock the file descriptor
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* table entry:
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*/
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_atomic_unlock(&_thread_fd_table[fd]->access_lock);
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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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* Lock the file descriptor
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* table entry again:
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*/
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_spinlock(&_thread_fd_table[fd]->access_lock);
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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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/* Unlock the file descriptor table entry: */
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_atomic_unlock(&_thread_fd_table[fd]->access_lock);
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}
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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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