freebsd-dev/lib/libpthread/thread/thr_sig.c
John Birrell 54059e9f3f Implementation of an additional state called SIGWAIT (with the previous
one renamed to SIGSUSPEND) to fix sigwait().

Submitted by: Daniel M. Eischen <eischen@vigrid.com>
1998-09-30 06:27:31 +00:00

336 lines
8.9 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 <signal.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"
/* Static variables: */
static int volatile yield_on_unlock_thread = 0;
static spinlock_t thread_link_list_lock = _SPINLOCK_INITIALIZER;
/* Lock the thread list: */
void
_lock_thread_list()
{
/* Lock the thread list: */
_SPINLOCK(&thread_link_list_lock);
}
/* Lock the thread list: */
void
_unlock_thread_list()
{
/* Unlock the thread list: */
_SPINUNLOCK(&thread_link_list_lock);
/*
* Check if a scheduler interrupt occurred while the thread
* list was locked:
*/
if (yield_on_unlock_thread) {
/* Reset the interrupt flag: */
yield_on_unlock_thread = 0;
/* This thread has overstayed it's welcome: */
sched_yield();
}
}
void
_thread_sig_handler(int sig, int code, struct sigcontext * scp)
{
char c;
int i;
pthread_t pthread;
/*
* Check if the pthread kernel has unblocked signals (or is about to)
* and was on its way into a _select when the current
* signal interrupted it:
*/
if (_thread_kern_in_select) {
/* Cast the signal number to a character variable: */
c = sig;
/*
* Write the signal number to the kernel pipe so that it will
* be ready to read when this signal handler returns. This
* means that the _select call will complete
* immediately.
*/
_thread_sys_write(_thread_kern_pipe[1], &c, 1);
}
/* Check if the signal requires a dump of thread information: */
if (sig == SIGINFO)
/* Dump thread information to file: */
_thread_dump_info();
/* Check if an interval timer signal: */
else if (sig == SIGVTALRM) {
/* Check if the scheduler interrupt has come at an
* unfortunate time which one of the threads is
* modifying the thread list:
*/
if (thread_link_list_lock.access_lock)
/*
* Set a flag so that the thread that has
* the lock yields when it unlocks the
* thread list:
*/
yield_on_unlock_thread = 1;
/*
* Check if the kernel has not been interrupted while
* executing scheduler code:
*/
else if (!_thread_kern_in_sched) {
/*
* Schedule the next thread. This function is not
* expected to return because it will do a longjmp
* instead.
*/
_thread_kern_sched(scp);
/*
* This point should not be reached, so abort the
* process:
*/
PANIC("Returned to signal function from scheduler");
}
} else {
/* Check if a child has terminated: */
if (sig == SIGCHLD) {
/*
* Go through the file list and set all files
* to non-blocking again in case the child
* set some of them to block. Sigh.
*/
for (i = 0; i < _thread_dtablesize; i++) {
/* Check if this file is used: */
if (_thread_fd_table[i] != NULL) {
/*
* Set the file descriptor to
* non-blocking:
*/
_thread_sys_fcntl(i, F_SETFL,
_thread_fd_table[i]->flags |
O_NONBLOCK);
}
}
}
/*
* POSIX says that pending SIGCONT signals are
* discarded when one of these signals occurs.
*/
if (sig == SIGTSTP || sig == SIGTTIN || sig == SIGTTOU) {
/*
* Enter a loop to discard pending SIGCONT
* signals:
*/
for (pthread = _thread_link_list;
pthread != NULL;
pthread = pthread->nxt)
sigdelset(&pthread->sigpend,SIGCONT);
}
/*
* Enter a loop to process each thread in the linked
* list that is sigwait-ing on a signal. Since POSIX
* doesn't specify which thread will get the signal
* if there are multiple waiters, we'll give it to the
* first one we find.
*/
for (pthread = _thread_link_list; pthread != NULL;
pthread = pthread->nxt) {
if ((pthread->state == PS_SIGWAIT) &&
sigismember(pthread->data.sigwait, sig)) {
/* Change the state of the thread to run: */
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
/* Return the signal number: */
pthread->signo = sig;
/*
* Do not attempt to deliver this signal
* to other threads.
*/
return;
}
}
/* Check if the signal is not being ignored: */
if (_thread_sigact[sig - 1].sa_handler != SIG_IGN)
/*
* Enter a loop to process each thread in the linked
* list:
*/
for (pthread = _thread_link_list; pthread != NULL;
pthread = pthread->nxt)
_thread_signal(pthread,sig);
/* Dispatch pending signals to the running thread: */
_dispatch_signals();
}
/* Returns nothing. */
return;
}
/* Perform thread specific actions in response to a signal: */
void
_thread_signal(pthread_t pthread, int sig)
{
/*
* Flag the signal as pending. It will be dispatched later.
*/
sigaddset(&pthread->sigpend,sig);
/*
* Process according to thread state:
*/
switch (pthread->state) {
/*
* States which do not change when a signal is trapped:
*/
case PS_COND_WAIT:
case PS_DEAD:
case PS_FDLR_WAIT:
case PS_FDLW_WAIT:
case PS_FILE_WAIT:
case PS_JOIN:
case PS_MUTEX_WAIT:
case PS_RUNNING:
case PS_STATE_MAX:
case PS_SIGTHREAD:
case PS_SIGWAIT:
case PS_SUSPENDED:
/* Nothing to do here. */
break;
/*
* The wait state is a special case due to the handling of
* SIGCHLD signals.
*/
case PS_WAIT_WAIT:
/*
* Check for signals other than the death of a child
* process:
*/
if (sig != SIGCHLD)
/* Flag the operation as interrupted: */
pthread->interrupted = 1;
/* Change the state of the thread to run: */
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
/* Return the signal number: */
pthread->signo = sig;
break;
/*
* States that are interrupted by the occurrence of a signal
* other than the scheduling alarm:
*/
case PS_FDR_WAIT:
case PS_FDW_WAIT:
case PS_SLEEP_WAIT:
case PS_SELECT_WAIT:
if (sig != SIGCHLD ||
_thread_sigact[sig - 1].sa_handler != SIG_DFL) {
/* Flag the operation as interrupted: */
pthread->interrupted = 1;
/* Change the state of the thread to run: */
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
/* Return the signal number: */
pthread->signo = sig;
}
break;
case PS_SIGSUSPEND:
/*
* Only wake up the thread if the signal is unblocked
* and there is a handler installed for the signal.
*/
if (!sigismember(&pthread->sigmask, sig) &&
_thread_sigact[sig - 1].sa_handler != SIG_DFL) {
/* Change the state of the thread to run: */
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
/* Return the signal number: */
pthread->signo = sig;
}
break;
}
}
/* Dispatch pending signals to the running thread: */
void
_dispatch_signals()
{
int i;
/*
* Check if there are pending signals for the running
* thread that aren't blocked:
*/
if ((_thread_run->sigpend & ~_thread_run->sigmask) != 0)
/* Look for all possible pending signals: */
for (i = 1; i < NSIG; i++)
/*
* Check that a custom handler is installed
* and if the signal is not blocked:
*/
if (_thread_sigact[i - 1].sa_handler != SIG_DFL &&
_thread_sigact[i - 1].sa_handler != SIG_IGN &&
sigismember(&_thread_run->sigpend,i) &&
!sigismember(&_thread_run->sigmask,i)) {
/* Clear the pending signal: */
sigdelset(&_thread_run->sigpend,i);
/*
* Dispatch the signal via the custom signal
* handler:
*/
(*(_thread_sigact[i - 1].sa_handler))(i);
}
}
#endif