4fc937ef8f
Before this change, a signal was delivered to each thread that
didn't have the signal masked. Signals also improperly woke up
threads waiting on I/O. With this change, signals are now
handled in the following way:
o If a thread is waiting in a sigwait for the signal,
then the thread is woken up.
o If no threads are sigwait'ing on the signal and a
thread is in a sigsuspend waiting for the signal,
then the thread is woken up.
o In the case that no threads are waiting or suspended
on the signal, then the signal is delivered to the
first thread we find that has the signal unmasked.
o If no threads are waiting or suspended on the signal,
and no threads have the signal unmasked, then the signal
is added to the process wide pending signal set. The
signal will be delivered to the first thread that unmasks
the signal.
If there is an installed signal handler, it is only invoked
if the chosen thread was not in a sigwait.
In the case that multiple threads are waiting or suspended
on a signal, or multiple threads have the signal unmasked,
we wake up/deliver the signal to the first thread we find.
The above rules still apply.
Reported by: Scott Hess <scott@avantgo.com>
Reviewed by: jb, jasone
150 lines
4.6 KiB
C
150 lines
4.6 KiB
C
/*
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* Copyright (c) 1997 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 <signal.h>
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#include <sys/param.h>
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#include <sys/signalvar.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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int
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sigwait(const sigset_t * set, int *sig)
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{
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int ret = 0;
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int i;
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sigset_t tempset, waitset;
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struct sigaction act;
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_thread_enter_cancellation_point();
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/*
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* Specify the thread kernel signal handler.
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*/
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act.sa_handler = (void (*) ()) _thread_sig_handler;
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act.sa_flags = SA_RESTART;
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act.sa_mask = *set;
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/* Ensure the scheduling signal is masked: */
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sigaddset(&act.sa_mask, _SCHED_SIGNAL);
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/*
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* Initialize the set of signals that will be waited on:
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*/
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waitset = *set;
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/* These signals can't be waited on. */
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sigdelset(&waitset, SIGKILL);
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sigdelset(&waitset, SIGSTOP);
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sigdelset(&waitset, _SCHED_SIGNAL);
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sigdelset(&waitset, SIGCHLD);
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sigdelset(&waitset, SIGINFO);
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/* Check to see if a pending signal is in the wait mask. */
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tempset = _thread_run->sigpend;
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SIGSETOR(tempset, _process_sigpending);
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SIGSETAND(tempset, waitset);
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if (SIGNOTEMPTY(tempset)) {
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/* Enter a loop to find a pending signal: */
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for (i = 1; i < NSIG; i++) {
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if (sigismember (&tempset, i))
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break;
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}
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/* Clear the pending signal: */
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if (sigismember(&_thread_run->sigpend,i))
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sigdelset(&_thread_run->sigpend,i);
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else
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sigdelset(&_process_sigpending,i);
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/* Return the signal number to the caller: */
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*sig = i;
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_thread_leave_cancellation_point();
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return (0);
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}
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/*
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* Enter a loop to find the signals that are SIG_DFL. For
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* these signals we must install a dummy signal handler in
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* order for the kernel to pass them in to us. POSIX says
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* that the _application_ must explicitly install a dummy
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* handler for signals that are SIG_IGN in order to sigwait
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* on them. Note that SIG_IGN signals are left in the
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* mask because a subsequent sigaction could enable an
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* ignored signal.
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*/
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for (i = 1; i < NSIG; i++) {
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if (sigismember(&waitset, i) &&
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(_thread_sigact[i - 1].sa_handler == SIG_DFL)) {
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if (_thread_sys_sigaction(i,&act,NULL) != 0)
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ret = -1;
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}
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}
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if (ret == 0) {
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/*
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* Save the wait signal mask. The wait signal
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* mask is independent of the threads signal mask
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* and requires separate storage.
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*/
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_thread_run->data.sigwait = &waitset;
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/* Wait for a signal: */
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_thread_kern_sched_state(PS_SIGWAIT, __FILE__, __LINE__);
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/* Return the signal number to the caller: */
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*sig = _thread_run->signo;
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/*
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* Probably unnecessary, but since it's in a union struct
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* we don't know how it could be used in the future.
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*/
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_thread_run->data.sigwait = NULL;
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}
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/* Restore the sigactions: */
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act.sa_handler = SIG_DFL;
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for (i = 1; i < NSIG; i++) {
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if (sigismember(&waitset, i) &&
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(_thread_sigact[i - 1].sa_handler == SIG_DFL)) {
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if (_thread_sys_sigaction(i,&act,NULL) != 0)
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ret = -1;
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}
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}
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_thread_leave_cancellation_point();
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/* Return the completion status: */
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return (ret);
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}
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#endif
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