3dc268f4e7
o Don't call signal handlers with the signal handler access lock
held.
o Remove pending signals before calling signal handlers. If
pending signals were not removed prior to handling them,
invocation of the handler could cause the handler to be
called more than once for the same signal. Found by: JB
o When SIGCHLD arrives, wake up all threads in PS_WAIT_WAIT
(wait4).
PR: bin/15328
Reviewed by: jasone
585 lines
15 KiB
C
585 lines
15 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 AUTHOR 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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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/types.h>
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#include <sys/signalvar.h>
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#include <signal.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <errno.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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/* Prototypes: */
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static void _thread_sig_check_state(pthread_t pthread, int sig);
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/* Static variables: */
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static spinlock_t signal_lock = _SPINLOCK_INITIALIZER;
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static unsigned int pending_sigs[NSIG];
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static unsigned int handled_sigs[NSIG];
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static int volatile check_pending = 0;
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/* Initialize signal handling facility: */
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void
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_thread_sig_init(void)
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{
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int i;
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/* Clear pending and handled signal counts: */
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for (i = 1; i < NSIG; i++) {
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pending_sigs[i - 1] = 0;
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handled_sigs[i - 1] = 0;
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}
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/* Clear the lock: */
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signal_lock.access_lock = 0;
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/* Clear the process pending signals: */
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sigemptyset(&_process_sigpending);
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}
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void
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_thread_sig_handler(int sig, int code, ucontext_t * scp)
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{
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pthread_t pthread;
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int i;
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char c;
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/* Check if an interval timer signal: */
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if (sig == _SCHED_SIGNAL) {
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if (_thread_kern_in_sched != 0) {
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/*
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* The scheduler is already running; ignore this
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* signal.
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*/
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}
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/*
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* Check if the scheduler interrupt has come when
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* the currently running thread has deferred thread
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* signals.
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*/
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else if (_thread_run->sig_defer_count > 0)
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_thread_run->yield_on_sig_undefer = 1;
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else {
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/*
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* Schedule the next thread. This function is not
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* expected to return because it will do a longjmp
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* instead.
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*/
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_thread_kern_sched(scp);
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/*
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* This point should not be reached, so abort the
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* process:
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*/
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PANIC("Returned to signal function from scheduler");
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}
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}
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/*
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* Check if the kernel has been interrupted while the scheduler
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* is accessing the scheduling queues or if there is a currently
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* running thread that has deferred signals.
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*/
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else if ((_queue_signals != 0) || ((_thread_kern_in_sched == 0) &&
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(_thread_run->sig_defer_count > 0))) {
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/* Cast the signal number to a character variable: */
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c = sig;
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/*
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* Write the signal number to the kernel pipe so that it will
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* be ready to read when this signal handler returns.
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*/
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_thread_sys_write(_thread_kern_pipe[1], &c, 1);
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/* Indicate that there are queued signals in the pipe. */
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_sigq_check_reqd = 1;
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}
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else {
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if (_atomic_lock(&signal_lock.access_lock)) {
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/* There is another signal handler running: */
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pending_sigs[sig - 1]++;
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check_pending = 1;
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}
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else {
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/* It's safe to handle the signal now. */
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pthread = _thread_sig_handle(sig, scp);
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/* Reset the pending and handled count back to 0: */
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pending_sigs[sig - 1] = 0;
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handled_sigs[sig - 1] = 0;
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if (pthread == NULL)
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signal_lock.access_lock = 0;
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else {
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sigaddset(&pthread->sigmask, sig);
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signal_lock.access_lock = 0;
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_thread_sig_deliver(pthread, sig);
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sigdelset(&pthread->sigmask, sig);
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}
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}
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/* Enter a loop to process pending signals: */
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while ((check_pending != 0) &&
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(_atomic_lock(&signal_lock.access_lock) == 0)) {
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check_pending = 0;
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for (i = 1; i < NSIG; i++) {
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if (pending_sigs[i - 1] > handled_sigs[i - 1]) {
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pending_sigs[i - 1] = handled_sigs[i - 1];
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pthread = _thread_sig_handle(i, scp);
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if (pthread != NULL) {
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sigaddset(&pthread->sigmask, i);
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signal_lock.access_lock = 0;
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_thread_sig_deliver(pthread, i);
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sigdelset(&pthread->sigmask, i);
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if (_atomic_lock(&signal_lock.access_lock)) {
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check_pending = 1;
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return;
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}
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}
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}
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}
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signal_lock.access_lock = 0;
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}
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}
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}
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pthread_t
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_thread_sig_handle(int sig, ucontext_t * scp)
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{
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int i;
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pthread_t pthread, pthread_next;
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pthread_t suspended_thread, signaled_thread;
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/* Check if the signal requires a dump of thread information: */
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if (sig == SIGINFO)
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/* Dump thread information to file: */
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_thread_dump_info();
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/* Check if an interval timer signal: */
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else if (sig == _SCHED_SIGNAL) {
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/*
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* This shouldn't ever occur (should this panic?).
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*/
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} else {
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/* Check if a child has terminated: */
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if (sig == SIGCHLD) {
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/*
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* Go through the file list and set all files
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* to non-blocking again in case the child
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* set some of them to block. Sigh.
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*/
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for (i = 0; i < _thread_dtablesize; i++) {
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/* Check if this file is used: */
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if (_thread_fd_table[i] != NULL) {
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/*
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* Set the file descriptor to
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* non-blocking:
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*/
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_thread_sys_fcntl(i, F_SETFL,
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_thread_fd_table[i]->flags |
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O_NONBLOCK);
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}
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}
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/*
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* Enter a loop to wake up all threads waiting
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* for a process to complete:
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*/
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for (pthread = TAILQ_FIRST(&_waitingq);
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pthread != NULL; pthread = pthread_next) {
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/*
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* Grab the next thread before possibly
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* destroying the link entry:
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*/
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pthread_next = TAILQ_NEXT(pthread, pqe);
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/*
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* If this thread is waiting for a child
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* process to complete, wake it up:
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*/
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if (pthread->state == PS_WAIT_WAIT) {
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/* Make the thread runnable: */
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PTHREAD_NEW_STATE(pthread,PS_RUNNING);
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/* Return the signal number: */
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pthread->signo = sig;
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}
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}
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}
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/*
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* POSIX says that pending SIGCONT signals are
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* discarded when one of these signals occurs.
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*/
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if (sig == SIGTSTP || sig == SIGTTIN || sig == SIGTTOU) {
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/*
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* Enter a loop to discard pending SIGCONT
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* signals:
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*/
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TAILQ_FOREACH(pthread, &_thread_list, tle) {
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sigdelset(&pthread->sigpend,SIGCONT);
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}
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}
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/*
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* Enter a loop to look for threads that have the
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* signal unmasked. POSIX specifies that a thread
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* in a sigwait will get the signal over any other
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* threads. Second preference will be threads in
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* in a sigsuspend. If none of the above, then the
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* signal is delivered to the first thread we find.
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*/
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suspended_thread = NULL;
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signaled_thread = NULL;
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for (pthread = TAILQ_FIRST(&_waitingq);
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pthread != NULL; pthread = pthread_next) {
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/*
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* Grab the next thread before possibly destroying
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* the link entry.
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*/
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pthread_next = TAILQ_NEXT(pthread, pqe);
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if ((pthread->state == PS_SIGWAIT) &&
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sigismember(pthread->data.sigwait, sig)) {
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/* Change the state of the thread to run: */
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PTHREAD_NEW_STATE(pthread,PS_RUNNING);
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/* Return the signal number: */
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pthread->signo = sig;
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/*
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* POSIX doesn't doesn't specify which thread
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* will get the signal if there are multiple
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* waiters, so we give it to the first thread
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* we find.
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*
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* Do not attempt to deliver this signal
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* to other threads.
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*/
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return (NULL);
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}
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else if (!sigismember(&pthread->sigmask, sig)) {
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if (pthread->state == PS_SIGSUSPEND) {
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if (suspended_thread == NULL)
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suspended_thread = pthread;
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} else if (signaled_thread == NULL)
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signaled_thread = pthread;
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}
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}
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/*
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* If we didn't find a thread in the waiting queue,
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* check the all threads queue:
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*/
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if (suspended_thread == NULL && signaled_thread == NULL) {
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/*
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* Enter a loop to look for other threads capable
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* of receiving the signal:
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*/
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TAILQ_FOREACH(pthread, &_thread_list, tle) {
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if (!sigismember(&pthread->sigmask, sig)) {
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signaled_thread = pthread;
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break;
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}
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}
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}
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/* Check if the signal is not being ignored: */
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if (_thread_sigact[sig - 1].sa_handler != SIG_IGN) {
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if (suspended_thread == NULL &&
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signaled_thread == NULL)
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/*
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* Add it to the set of signals pending
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* on the process:
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*/
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sigaddset(&_process_sigpending, sig);
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else {
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/*
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* We only deliver the signal to one thread;
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* give preference to the suspended thread:
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*/
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if (suspended_thread != NULL)
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pthread = suspended_thread;
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else
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pthread = signaled_thread;
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/*
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* Perform any state changes due to signal
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* arrival:
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*/
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_thread_sig_check_state(pthread, sig);
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return (pthread);
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}
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}
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}
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/* Returns nothing. */
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return (NULL);
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}
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/* Perform thread specific actions in response to a signal: */
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static void
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_thread_sig_check_state(pthread_t pthread, int sig)
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{
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/*
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* Process according to thread state:
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*/
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switch (pthread->state) {
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/*
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* States which do not change when a signal is trapped:
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*/
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case PS_COND_WAIT:
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case PS_DEAD:
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case PS_DEADLOCK:
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case PS_FDLR_WAIT:
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case PS_FDLW_WAIT:
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case PS_FILE_WAIT:
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case PS_JOIN:
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case PS_MUTEX_WAIT:
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case PS_RUNNING:
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case PS_STATE_MAX:
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case PS_SIGTHREAD:
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case PS_SPINBLOCK:
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case PS_SUSPENDED:
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/* Increment the pending signal count. */
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sigaddset(&pthread->sigpend,sig);
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break;
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case PS_SIGWAIT:
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/* Wake up the thread if the signal is blocked. */
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if (sigismember(pthread->data.sigwait, sig)) {
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/* Change the state of the thread to run: */
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PTHREAD_NEW_STATE(pthread,PS_RUNNING);
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/* Return the signal number: */
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pthread->signo = sig;
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} else
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/* Increment the pending signal count. */
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sigaddset(&pthread->sigpend,sig);
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break;
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/*
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* The wait state is a special case due to the handling of
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* SIGCHLD signals.
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*/
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case PS_WAIT_WAIT:
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/*
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* Check for signals other than the death of a child
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* process:
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*/
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if (sig != SIGCHLD)
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/* Flag the operation as interrupted: */
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pthread->interrupted = 1;
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/* Change the state of the thread to run: */
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PTHREAD_NEW_STATE(pthread,PS_RUNNING);
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/* Return the signal number: */
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pthread->signo = sig;
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break;
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/*
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* States that are interrupted by the occurrence of a signal
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* other than the scheduling alarm:
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*/
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case PS_FDR_WAIT:
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case PS_FDW_WAIT:
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case PS_POLL_WAIT:
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case PS_SLEEP_WAIT:
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case PS_SELECT_WAIT:
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if ((_thread_sigact[sig - 1].sa_flags & SA_RESTART) == 0) {
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/* Flag the operation as interrupted: */
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pthread->interrupted = 1;
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if (pthread->flags & PTHREAD_FLAGS_IN_WORKQ)
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PTHREAD_WORKQ_REMOVE(pthread);
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/* Change the state of the thread to run: */
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PTHREAD_NEW_STATE(pthread,PS_RUNNING);
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/* Return the signal number: */
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pthread->signo = sig;
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}
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break;
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case PS_SIGSUSPEND:
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/*
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* Only wake up the thread if there is a handler installed
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* for the signal.
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*/
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if (_thread_sigact[sig - 1].sa_handler != SIG_DFL) {
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/* Change the state of the thread to run: */
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PTHREAD_NEW_STATE(pthread,PS_RUNNING);
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/* Return the signal number: */
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pthread->signo = sig;
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}
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break;
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}
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}
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/* Send a signal to a specific thread (ala pthread_kill): */
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void
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_thread_sig_send(pthread_t pthread, int sig)
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{
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/*
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* Check that the signal is not being ignored:
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*/
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if (_thread_sigact[sig - 1].sa_handler != SIG_IGN) {
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if (pthread->state == PS_SIGWAIT &&
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sigismember(pthread->data.sigwait, sig)) {
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/* Change the state of the thread to run: */
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PTHREAD_NEW_STATE(pthread,PS_RUNNING);
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/* Return the signal number: */
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pthread->signo = sig;
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} else if (pthread->state != PS_SIGWAIT &&
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!sigismember(&pthread->sigmask, sig)) {
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/* Perform any state changes due to signal arrival: */
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_thread_sig_check_state(pthread, sig);
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/* Call the installed signal handler: */
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_thread_sig_deliver(pthread, sig);
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}
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else {
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/* Increment the pending signal count. */
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sigaddset(&pthread->sigpend,sig);
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}
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}
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}
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/* Dispatch pending signals to the running thread: */
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void
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_dispatch_signals()
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{
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sigset_t sigset, mask;
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int i;
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/*
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* Check if there are pending signals for the running
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* thread or process that aren't blocked:
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*/
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sigset = _thread_run->sigpend;
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SIGSETOR(sigset, _process_sigpending);
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SIGSETNAND(sigset, _thread_run->sigmask);
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if (SIGNOTEMPTY(sigset)) {
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/*
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* Enter a loop to calculate deliverable pending signals
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* before actually delivering them. The pending signals
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* must be removed from the pending signal sets before
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* calling the signal handler because the handler may
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* call library routines that again check for and deliver
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* pending signals.
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*/
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for (i = 1; i < NSIG; i++) {
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/*
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* Check that a custom handler is installed
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* and if the signal is not blocked:
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*/
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if (_thread_sigact[i - 1].sa_handler != SIG_DFL &&
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_thread_sigact[i - 1].sa_handler != SIG_IGN &&
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sigismember(&sigset, i)) {
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if (sigismember(&_thread_run->sigpend,i))
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/* Clear the thread pending signal: */
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sigdelset(&_thread_run->sigpend,i);
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else
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/* Clear the process pending signal: */
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sigdelset(&_process_sigpending,i);
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}
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else
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/* Remove the signal if it can't be handled: */
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sigdelset(&sigset, i);
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}
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/* Now deliver the signals: */
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for (i = 1; i < NSIG; i++) {
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if (sigismember(&sigset, i))
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/* Deliver the signal to the running thread: */
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_thread_sig_deliver(_thread_run, i);
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}
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}
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}
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/* Deliver a signal to a thread: */
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void
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_thread_sig_deliver(pthread_t pthread, int sig)
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{
|
|
sigset_t mask;
|
|
pthread_t pthread_saved;
|
|
|
|
/*
|
|
* Check that a custom handler is installed
|
|
* and if the signal is not blocked:
|
|
*/
|
|
if (_thread_sigact[sig - 1].sa_handler != SIG_DFL &&
|
|
_thread_sigact[sig - 1].sa_handler != SIG_IGN) {
|
|
/* Save the current thread: */
|
|
pthread_saved = _thread_run;
|
|
|
|
/* Save the threads signal mask: */
|
|
mask = pthread->sigmask;
|
|
|
|
/*
|
|
* Add the current signal and signal handler
|
|
* mask to the threads current signal mask:
|
|
*/
|
|
SIGSETOR(pthread->sigmask, _thread_sigact[sig - 1].sa_mask);
|
|
sigaddset(&pthread->sigmask, sig);
|
|
|
|
/* Current thread inside critical region? */
|
|
if (_thread_run->sig_defer_count > 0)
|
|
pthread->sig_defer_count++;
|
|
|
|
_thread_run = pthread;
|
|
|
|
/*
|
|
* Dispatch the signal via the custom signal
|
|
* handler:
|
|
*/
|
|
(*(_thread_sigact[sig - 1].sa_handler))(sig);
|
|
|
|
_thread_run = pthread_saved;
|
|
|
|
/* Current thread inside critical region? */
|
|
if (_thread_run->sig_defer_count > 0)
|
|
pthread->sig_defer_count--;
|
|
|
|
/* Restore the threads signal mask: */
|
|
pthread->sigmask = mask;
|
|
}
|
|
}
|
|
#endif
|