path: root/lib/libc_r/uthread/uthread_sig.c

/*	$OpenBSD: uthread_sig.c,v 1.12 2001/12/31 18:23:15 fgsch Exp $	*/
/*
 * 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 AUTHOR 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.
 *
 * $FreeBSD: uthread_sig.c,v 1.20 1999/09/29 15:18:39 marcel Exp $
 */
#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 spinlock_t	signal_lock = _SPINLOCK_INITIALIZER;
unsigned int		pending_sigs[NSIG];
unsigned int		handled_sigs[NSIG];
int			volatile check_pending = 0;

/* Initialize signal handling facility: */
void
_thread_sig_init(void)
{
	int i;

	/* Clear pending and handled signal counts: */
	for (i = 1; i < NSIG; i++) {
		pending_sigs[i - 1] = 0;
		handled_sigs[i - 1] = 0;
	}

	/* Clear the lock: */
	signal_lock.access_lock = 0;
}

void
_thread_sig_handler(int sig, int code, struct sigcontext * scp)
{
	struct pthread	*curthread = _get_curthread();
	char	c;
	int	i;

	/* Check if an interval timer signal: */
	if (sig == _SCHED_SIGNAL) {
		/* Update the scheduling clock: */
		gettimeofday((struct timeval *)&_sched_tod, NULL);
		_sched_ticks++;

		if (_thread_kern_in_sched != 0) {
			/*
			 * The scheduler is already running; ignore this
			 * signal.
			 */
		}
		/*
		 * Check if the scheduler interrupt has come when
		 * the currently running thread has deferred thread
		 * signals.
		 */
		else if (curthread->sig_defer_count > 0)
			curthread->yield_on_sig_undefer = 1;

		else {
			/*
			 * Schedule the next thread. This function is not
			 * expected to return because it will do a longjmp
			 * instead.
			 */
			_thread_kern_sched(scp);

			/* The scheduler currently returns here instead
			   of calling sigreturn due to a sparc sigreturn
			   bug.   We should also return.   That brings
			   us back to the sigtramp code which will
			   sigreturn to the context stored on the current
			   stack (which is the same as scp, above).
			   The code originally did this:

			   PANIC("Returned to signal function from scheduler");
			*/
			return;
		}
	}
	/*
	 * Check if the kernel has been interrupted while the scheduler
	 * is accessing the scheduling queues or if there is a currently
	 * running thread that has deferred signals.
	 */
	else if ((_queue_signals != 0) || ((_thread_kern_in_sched == 0) &&
	    (curthread->sig_defer_count > 0))) {
		/* 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.
		 */
		_thread_sys_write(_thread_kern_pipe[1], &c, 1);

		/* Indicate that there are queued signals in the pipe. */
		_sigq_check_reqd = 1;
	}
	else {
		if (_atomic_lock(&signal_lock.access_lock)) {
			/* There is another signal handler running: */
			pending_sigs[sig - 1]++;
			check_pending = 1;
		}
		else {
			/* It's safe to handle the signal now. */
			_thread_sig_handle(sig, scp);

			/* Reset the pending and handled count back to 0: */
			pending_sigs[sig - 1] = 0;
			handled_sigs[sig - 1] = 0;

			signal_lock.access_lock = 0;
		}

		/* Enter a loop to process pending signals: */
		while ((check_pending != 0) &&
		    (_atomic_lock(&signal_lock.access_lock) == 0)) {
			check_pending = 0;
			for (i = 1; i < NSIG; i++) {
				if (pending_sigs[i - 1] > handled_sigs[i - 1])
					_thread_sig_handle(i, scp);
			}
			signal_lock.access_lock = 0;
		}
	}
}

void
_thread_sig_handle(int sig, struct sigcontext * scp)
{
	struct pthread	*curthread = _get_curthread();
	int		i;
	pthread_t	pthread, pthread_next;

	/* 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 == _SCHED_SIGNAL) {
		/*
		 * This shouldn't ever occur (should this panic?).
		 */
	} 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:
			 */
			TAILQ_FOREACH(pthread, &_thread_list, tle) {
				sigdelset(&pthread->sigpend,SIGCONT);
			}
		}

		/*
		 * Enter a loop to process each thread in the waiting
		 * 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 = TAILQ_FIRST(&_waitingq);
		    pthread != NULL; pthread = pthread_next) {
			/*
			 * Grab the next thread before possibly destroying
			 * the link entry.
			 */
			pthread_next = TAILQ_NEXT(pthread, pqe);

			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:
			 */
			TAILQ_FOREACH(pthread, &_thread_list, tle) {
				pthread_t pthread_saved = curthread;

				/* Current thread inside critical region? */
				if (curthread->sig_defer_count > 0)
					pthread->sig_defer_count++;

				_thread_signal(pthread,sig);

				/*
				 * Dispatch pending signals to the
				 * running thread:
				 */
				_set_curthread(pthread);
				_dispatch_signals();
				_set_curthread(pthread_saved);

				/* Current thread inside critical region? */
				if (curthread->sig_defer_count > 0)
					pthread->sig_defer_count--;
			}
	}

	/* 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 may be dispatched later.
	 */
	sigaddset(&pthread->sigpend,sig);

	/* skip this thread if signal is masked */
	if (sigismember(&pthread->sigmask, sig))
		return;

	/*
	 * 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_SIGTHREAD:
	case PS_SIGWAIT:
	case PS_SUSPENDED:
	case PS_SPINBLOCK:
	case PS_DEADLOCK:
		/* 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_POLL_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;

			if (pthread->flags & PTHREAD_FLAGS_IN_WORKQ)
				PTHREAD_WORKQ_REMOVE(pthread);

			/* 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 (_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()
{
	struct pthread	*curthread = _get_curthread();
	int i;

	/*
	 * Check if there are pending signals for the running
	 * thread that aren't blocked:
	 */
	if ((curthread->sigpend & ~curthread->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(&curthread->sigpend,i) &&
			    !sigismember(&curthread->sigmask,i)) {
				/* Clear the pending signal: */
				sigdelset(&curthread->sigpend,i);

				/*
				 * Dispatch the signal via the custom signal
				 * handler:
				 */
				(*(_thread_sigact[i - 1].sa_handler))(i);
			}
}
#endif