58a7cc5d1b
o Runnable threads are now maintained in priority queues. The
implementation requires two things:
1.) The priority queues must be protected during insertion
and removal of threads. Since the kernel scheduler
must modify the priority queues, a spinlock for
protection cannot be used. The functions
_thread_kern_sched_defer() and _thread_kern_sched_undefer()
were added to {un}defer kernel scheduler activation.
2.) A thread (active) priority change can be performed only
when the thread is removed from the priority queue. The
implementation uses a threads active priority when
inserting it into the queue.
A by-product is that thread switches are much faster. A
separate queue is used for waiting and/or blocked threads,
and it is searched at most 2 times in the kernel scheduler
when there are active threads. It should be possible to
reduce this to once by combining polling of threads waiting
on I/O with the loop that looks for timed out threads and
the minimum timeout value.
o Functions to defer kernel scheduler activation were added. These
are _thread_kern_sched_defer() and _thread_kern_sched_undefer()
and may be called recursively. These routines do not block the
scheduling signal, but latch its occurrence. The signal handler
will not call the kernel scheduler when the running thread has
deferred scheduling, but it will be called when running thread
undefers scheduling.
o Added support for _POSIX_THREAD_PRIORITY_SCHEDULING. All the
POSIX routines required by this should now be implemented.
One note, SCHED_OTHER, SCHED_FIFO, and SCHED_RR are required
to be defined by including pthread.h. These defines are currently
in sched.h. I modified pthread.h to include sched.h but don't
know if this is the proper thing to do.
o Added support for priority protection and inheritence mutexes.
This allows definition of _POSIX_THREAD_PRIO_PROTECT and
_POSIX_THREAD_PRIO_INHERIT.
o Added additional error checks required by POSIX for mutexes and
condition variables.
o Provided a wrapper for sigpending which is marked as a hidden
syscall.
o Added a non-portable function as a debugging aid to allow an
application to monitor thread context switches. An application
can install a routine that gets called everytime a thread
(explicitly created by the application) gets context switched.
The routine gets passed the pthread IDs of the threads that are
being switched in and out.
Submitted by: Dan Eischen <eischen@vigrid.com>
Changes by me:
o Added a PS_SPINBLOCK state to deal with the priority inversion
problem most often (I think) seen by threads calling malloc/free/realloc.
o Dispatch signals to the running thread directly rather than at a
context switch to avoid the situation where the switch never occurs.
164 lines
5.3 KiB
C
164 lines
5.3 KiB
C
/*
|
|
* 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 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 <errno.h>
|
|
#include <string.h>
|
|
#include <unistd.h>
|
|
#include <fcntl.h>
|
|
#ifdef _THREAD_SAFE
|
|
#include <pthread.h>
|
|
#include "pthread_private.h"
|
|
|
|
pid_t
|
|
fork(void)
|
|
{
|
|
int i, flags;
|
|
pid_t ret;
|
|
pthread_t pthread;
|
|
pthread_t pthread_next;
|
|
|
|
/* Lock the thread list: */
|
|
_lock_thread_list();
|
|
|
|
/* Fork a new process: */
|
|
if ((ret = _thread_sys_fork()) != 0) {
|
|
/* Parent process or error. Nothing to do here. */
|
|
} else {
|
|
/* Close the pthread kernel pipe: */
|
|
_thread_sys_close(_thread_kern_pipe[0]);
|
|
_thread_sys_close(_thread_kern_pipe[1]);
|
|
|
|
/* Reset signals pending for the running thread: */
|
|
_thread_run->sigpend = 0;
|
|
|
|
/*
|
|
* Create a pipe that is written to by the signal handler to
|
|
* prevent signals being missed in calls to
|
|
* _thread_sys_select:
|
|
*/
|
|
if (_thread_sys_pipe(_thread_kern_pipe) != 0) {
|
|
/* Cannot create pipe, so abort: */
|
|
PANIC("Cannot create pthread kernel pipe for forked process");
|
|
}
|
|
/* Get the flags for the read pipe: */
|
|
else if ((flags = _thread_sys_fcntl(_thread_kern_pipe[0], F_GETFL, NULL)) == -1) {
|
|
/* Abort this application: */
|
|
abort();
|
|
}
|
|
/* Make the read pipe non-blocking: */
|
|
else if (_thread_sys_fcntl(_thread_kern_pipe[0], F_SETFL, flags | O_NONBLOCK) == -1) {
|
|
/* Abort this application: */
|
|
abort();
|
|
}
|
|
/* Get the flags for the write pipe: */
|
|
else if ((flags = _thread_sys_fcntl(_thread_kern_pipe[1], F_GETFL, NULL)) == -1) {
|
|
/* Abort this application: */
|
|
abort();
|
|
}
|
|
/* Make the write pipe non-blocking: */
|
|
else if (_thread_sys_fcntl(_thread_kern_pipe[1], F_SETFL, flags | O_NONBLOCK) == -1) {
|
|
/* Abort this application: */
|
|
abort();
|
|
/* Initialize the ready queue: */
|
|
} else if (_pq_init(&_readyq, PTHREAD_MIN_PRIORITY,
|
|
PTHREAD_MAX_PRIORITY) != 0) {
|
|
/* Abort this application: */
|
|
PANIC("Cannot allocate priority ready queue.");
|
|
} else {
|
|
/* Point to the first thread in the list: */
|
|
pthread = _thread_link_list;
|
|
|
|
/*
|
|
* Enter a loop to remove all threads other than
|
|
* the running thread from the thread list:
|
|
*/
|
|
while (pthread != NULL) {
|
|
pthread_next = pthread->nxt;
|
|
if (pthread == _thread_run) {
|
|
_thread_link_list = pthread;
|
|
pthread->nxt = NULL;
|
|
} else {
|
|
if (pthread->attr.stackaddr_attr ==
|
|
NULL && pthread->stack != NULL)
|
|
/*
|
|
* Free the stack of the
|
|
* dead thread:
|
|
*/
|
|
free(pthread->stack);
|
|
|
|
if (pthread->specific_data != NULL)
|
|
free(pthread->specific_data);
|
|
|
|
free(pthread);
|
|
}
|
|
|
|
/* Point to the next thread: */
|
|
pthread = pthread_next;
|
|
}
|
|
|
|
/* Re-init the waiting queues. */
|
|
TAILQ_INIT(&_waitingq);
|
|
|
|
/* Initialize the scheduling switch hook routine: */
|
|
_sched_switch_hook = NULL;
|
|
|
|
/* Clear out any locks in the file descriptor table: */
|
|
for (i = 0; i < _thread_dtablesize; i++) {
|
|
if (_thread_fd_table[i] != NULL) {
|
|
/* Initialise the file locks: */
|
|
memset(&_thread_fd_table[i]->lock, 0,
|
|
sizeof(_thread_fd_table[i]->lock));
|
|
_thread_fd_table[i]->r_owner = NULL;
|
|
_thread_fd_table[i]->w_owner = NULL;
|
|
_thread_fd_table[i]->r_fname = NULL;
|
|
_thread_fd_table[i]->w_fname = NULL;
|
|
_thread_fd_table[i]->r_lineno = 0;;
|
|
_thread_fd_table[i]->w_lineno = 0;;
|
|
_thread_fd_table[i]->r_lockcount = 0;;
|
|
_thread_fd_table[i]->w_lockcount = 0;;
|
|
|
|
/* Initialise the read/write queues: */
|
|
_thread_queue_init(&_thread_fd_table[i]->r_queue);
|
|
_thread_queue_init(&_thread_fd_table[i]->w_queue);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Unock the thread list: */
|
|
_unlock_thread_list();
|
|
|
|
/* Return the process ID: */
|
|
return (ret);
|
|
}
|
|
#endif
|