freebsd-nq/lib/libc_r/uthread/uthread_exit.c
John Birrell 58a7cc5d1b [ The author's description... ]
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.
1999-03-23 05:07:56 +00:00

178 lines
5.4 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 <unistd.h>
#include <fcntl.h>
#include <string.h>
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"
void _exit(int status)
{
int flags;
int i;
struct itimerval itimer;
/* Disable the interval timer: */
itimer.it_interval.tv_sec = 0;
itimer.it_interval.tv_usec = 0;
itimer.it_value.tv_sec = 0;
itimer.it_value.tv_usec = 0;
setitimer(_ITIMER_SCHED_TIMER, &itimer, NULL);
/* Close the pthread kernel pipe: */
_thread_sys_close(_thread_kern_pipe[0]);
_thread_sys_close(_thread_kern_pipe[1]);
/*
* Enter a loop to set all file descriptors to blocking
* if they were not created as non-blocking:
*/
for (i = 0; i < _thread_dtablesize; i++) {
/* Check if this file descriptor is in use: */
if (_thread_fd_table[i] != NULL &&
!(_thread_fd_table[i]->flags & O_NONBLOCK)) {
/* Get the current flags: */
flags = _thread_sys_fcntl(i, F_GETFL, NULL);
/* Clear the nonblocking file descriptor flag: */
_thread_sys_fcntl(i, F_SETFL, flags & ~O_NONBLOCK);
}
}
/* Call the _exit syscall: */
_thread_sys__exit(status);
}
void
_thread_exit(char *fname, int lineno, char *string)
{
char s[256];
/* Prepare an error message string: */
strcpy(s, "Fatal error '");
strcat(s, string);
strcat(s, "' at line ? ");
strcat(s, "in file ");
strcat(s, fname);
strcat(s, " (errno = ?");
strcat(s, ")\n");
/* Write the string to the standard error file descriptor: */
_thread_sys_write(2, s, strlen(s));
/* Force this process to exit: */
_exit(1);
}
void
pthread_exit(void *status)
{
int sig;
long l;
pthread_t pthread;
/* Check if this thread is already in the process of exiting: */
if ((_thread_run->flags & PTHREAD_EXITING) != 0) {
char msg[128];
snprintf(msg,"Thread %p has called pthread_exit() from a destructor. POSIX 1003.1 1996 s16.2.5.2 does not allow this!",_thread_run);
PANIC(msg);
}
/* Flag this thread as exiting: */
_thread_run->flags |= PTHREAD_EXITING;
/* Save the return value: */
_thread_run->ret = status;
while (_thread_run->cleanup != NULL) {
pthread_cleanup_pop(1);
}
if (_thread_run->attr.cleanup_attr != NULL) {
_thread_run->attr.cleanup_attr(_thread_run->attr.arg_attr);
}
/* Check if there is thread specific data: */
if (_thread_run->specific_data != NULL) {
/* Run the thread-specific data destructors: */
_thread_cleanupspecific();
}
/*
* Guard against preemption by a scheduling signal. A change of
* thread state modifies the waiting and priority queues.
*/
_thread_kern_sched_defer();
/* Check if there are any threads joined to this one: */
while ((pthread = _thread_queue_deq(&(_thread_run->join_queue))) != NULL) {
/* Wake the joined thread and let it detach this thread: */
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
}
/*
* Reenable preemption and yield if a scheduling signal
* occurred while in the critical region.
*/
_thread_kern_sched_undefer();
/*
* Lock the garbage collector mutex to ensure that the garbage
* collector is not using the dead thread list.
*/
if (pthread_mutex_lock(&_gc_mutex) != 0)
PANIC("Cannot lock gc mutex");
/* Add this thread to the list of dead threads. */
_thread_run->nxt_dead = _thread_dead;
_thread_dead = _thread_run;
/*
* Signal the garbage collector thread that there is something
* to clean up.
*/
if (pthread_cond_signal(&_gc_cond) != 0)
PANIC("Cannot signal gc cond");
/* Unlock the garbage collector mutex: */
if (pthread_mutex_unlock(&_gc_mutex) != 0)
PANIC("Cannot lock gc mutex");
/* This this thread will never be re-scheduled. */
_thread_kern_sched_state(PS_DEAD, __FILE__, __LINE__);
/* This point should not be reached. */
PANIC("Dead thread has resumed");
}
#endif