Date: Sun, 30 Aug 1998 18:50:02 -0700 (PDT) From: "Daniel M. Eischen" <eischen@vigrid.com> To: freebsd-bugs@FreeBSD.ORG Subject: Re: kern/7586: [PATCH] Threads bug in libc_r preventing MySQL from shutting down Message-ID: <199808310150.SAA06643@freefall.freebsd.org>
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The following reply was made to PR kern/7586; it has been noted by GNATS.
From: "Daniel M. Eischen" <eischen@vigrid.com>
To: freebsd-gnats-submit@freebsd.org, nik@iii.co.uk
Cc: jb@freebsd.org
Subject: Re: kern/7586: [PATCH] Threads bug in libc_r preventing MySQL from shutting down
Date: Sun, 30 Aug 1998 17:41:26 -0400
This is a multi-part message in MIME format.
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Here is a fix for the sigsuspend and sigwait problems. Sigsuspend and
sigwait cannot use the same "waiting" mask. In the case of sigwait,
the "waiting" mask is independent of the threads mask.
I attach patches to the most recent threads library, and to test/sigwait
to cover more test cases. I also include a separate program for testing
sigsuspend. I guess the idea is to put these test cases in
libc_r/test/.
This should fix the reported MySQL shutdown problem. Someone
should test this as I don't have MySQL installed.
Dan Eischen
eischen@vigrid.com
--------------446B9B3D2781E494167EB0E7
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Common subdirectories: ../uthread.orig/CVS and ./CVS
diff -c ../uthread.orig/pthread_private.h ./pthread_private.h
*** ../uthread.orig/pthread_private.h Tue Jun 9 19:02:43 1998
--- ./pthread_private.h Sat Aug 29 19:51:30 1998
***************
*** 240,245 ****
--- 240,246 ----
PS_SELECT_WAIT,
PS_SLEEP_WAIT,
PS_WAIT_WAIT,
+ PS_SIGSUSPEND,
PS_SIGWAIT,
PS_JOIN,
PS_SUSPENDED,
diff -c ../uthread.orig/uthread_kill.c ./uthread_kill.c
*** ../uthread.orig/uthread_kill.c Tue Aug 25 07:19:14 1998
--- ./uthread_kill.c Sat Aug 29 19:33:30 1998
***************
*** 46,63 ****
/* Invalid signal: */
ret = EINVAL;
/* Find the thread in the list of active threads: */
else if ((ret = _find_thread(pthread)) == 0) {
! if ((pthread->state == PS_SIGWAIT) &&
! sigismember(&pthread->sigmask, sig)) {
! /* Change the state of the thread to run: */
! PTHREAD_NEW_STATE(pthread,PS_RUNNING);
! /* Return the signal number: */
! pthread->signo = sig;
! } else
/* Increment the pending signal count: */
sigaddset(&pthread->sigpend,sig);
}
/* Return the completion status: */
--- 46,96 ----
/* Invalid signal: */
ret = EINVAL;
+ /* Ignored signals get dropped on the floor. */
+ else if (_thread_sigact[sig - 1].sa_handler == SIG_IGN)
+ ret = 0;
+
/* Find the thread in the list of active threads: */
else if ((ret = _find_thread(pthread)) == 0) {
! switch (pthread->state) {
! 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;
! }
! /* Increment the pending signal count: */
! sigaddset(&pthread->sigpend,sig);
! break;
!
! case PS_SIGWAIT:
! /* Wake up the thread if the signal is blocked. */
! if (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;
! }
! else
! /*
! * Increment the pending signal count.
! */
! sigaddset(&pthread->sigpend,sig);
! break;
! default:
/* Increment the pending signal count: */
sigaddset(&pthread->sigpend,sig);
+ break;
+ }
}
/* Return the completion status: */
diff -c ../uthread.orig/uthread_sig.c ./uthread_sig.c
*** ../uthread.orig/uthread_sig.c Wed Aug 26 16:50:42 1998
--- ./uthread_sig.c Sat Aug 29 19:37:19 1998
***************
*** 199,205 ****
/*
* POSIX says that pending SIGCONT signals are
! * discarded when one of there signals occurs.
*/
if (sig == SIGTSTP || sig == SIGTTIN || sig == SIGTTOU) {
/*
--- 199,205 ----
/*
* POSIX says that pending SIGCONT signals are
! * discarded when one of these signals occurs.
*/
if (sig == SIGTSTP || sig == SIGTTIN || sig == SIGTTOU) {
/*
***************
*** 212,217 ****
--- 212,242 ----
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)
/*
***************
*** 258,263 ****
--- 283,289 ----
case PS_MUTEX_WAIT:
case PS_RUNNING:
case PS_STATE_MAX:
+ case PS_SIGWAIT:
case PS_SIGTHREAD:
case PS_SUSPENDED:
/* Nothing to do here. */
***************
*** 283,288 ****
--- 309,328 ----
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;
/*
* States that are interrupted by the occurrence of a signal
* other than the scheduling alarm:
***************
*** 291,297 ****
case PS_FDW_WAIT:
case PS_SLEEP_WAIT:
case PS_SELECT_WAIT:
- case PS_SIGWAIT:
if (sig != SIGCHLD ||
_thread_sigact[sig - 1].sa_handler != SIG_DFL) {
/* Flag the operation as interrupted: */
--- 331,336 ----
diff -c ../uthread.orig/uthread_sigsuspend.c ./uthread_sigsuspend.c
*** ../uthread.orig/uthread_sigsuspend.c Wed Apr 29 05:59:24 1998
--- ./uthread_sigsuspend.c Sat Aug 29 19:43:22 1998
***************
*** 44,57 ****
/* Check if a new signal set was provided by the caller: */
if (set != NULL) {
! /* Save the current sigmal mask: */
oset = _thread_run->sigmask;
! /* Combine the caller's mask with the current one: */
! _thread_run->sigmask |= *set;
/* Wait for a signal: */
! _thread_kern_sched_state(PS_SIGWAIT, __FILE__, __LINE__);
/* Always return an interrupted error: */
errno = EINTR;
--- 44,57 ----
/* Check if a new signal set was provided by the caller: */
if (set != NULL) {
! /* Save the current signal mask: */
oset = _thread_run->sigmask;
! /* Change the caller's mask: */
! _thread_run->sigmask = *set;
/* Wait for a signal: */
! _thread_kern_sched_state(PS_SIGSUSPEND, __FILE__, __LINE__);
/* Always return an interrupted error: */
errno = EINTR;
diff -c ../uthread.orig/uthread_sigwait.c ./uthread_sigwait.c
*** ../uthread.orig/uthread_sigwait.c Tue Aug 25 07:19:14 1998
--- ./uthread_sigwait.c Sun Aug 30 21:00:04 1998
***************
*** 41,47 ****
{
int ret = 0;
int i;
! sigset_t oset;
struct sigaction act;
/*
--- 41,47 ----
{
int ret = 0;
int i;
! sigset_t tempset;
struct sigaction act;
/*
***************
*** 60,90 ****
sigdelset(&act.sa_mask, SIGCHLD);
sigdelset(&act.sa_mask, SIGINFO);
/*
* Enter a loop to find the signals that are SIG_DFL. For
* these signals we must install a dummy signal handler in
* order for the kernel to pass them in to us. POSIX says
* that the application must explicitly install a dummy
* handler for signals that are SIG_IGN in order to sigwait
! * on them, so we ignore SIG_IGN signals.
*/
for (i = 1; i < NSIG; i++) {
if (sigismember(&act.sa_mask, i)) {
! if (_thread_sigact[i - 1].sa_handler == SIG_DFL) {
if (_thread_sys_sigaction(i,&act,NULL) != 0)
ret = -1;
- }
- else if (_thread_sigact[i - 1].sa_handler == SIG_IGN)
- sigdelset(&act.sa_mask, i);
}
}
- if (ret == 0) {
! /* Save the current signal mask: */
! oset = _thread_run->sigmask;
! /* Combine the caller's mask with the current one: */
! _thread_run->sigmask |= act.sa_mask;
/* Wait for a signal: */
_thread_kern_sched_state(PS_SIGWAIT, __FILE__, __LINE__);
--- 60,108 ----
sigdelset(&act.sa_mask, SIGCHLD);
sigdelset(&act.sa_mask, SIGINFO);
+ /* Check to see if a pending signal is in the wait mask. */
+ if (tempset = (_thread_run->sigpend & act.sa_mask)) {
+ /* Enter a loop to find a pending signal: */
+ for (i = 1; i < NSIG; i++) {
+ if (sigismember (&tempset, i))
+ break;
+ }
+
+ /* Clear the pending signal: */
+ sigdelset(&_thread_run->sigpend,i);
+
+ /* Return the signal number to the caller: */
+ *sig = i;
+
+ return (0);
+ }
+
/*
* Enter a loop to find the signals that are SIG_DFL. For
* these signals we must install a dummy signal handler in
* order for the kernel to pass them in to us. POSIX says
* that the application must explicitly install a dummy
* handler for signals that are SIG_IGN in order to sigwait
! * on them. Note that SIG_IGN signals are left in the
! * mask because a subsequent sigaction could enable an
! * ignored signal.
*/
for (i = 1; i < NSIG; i++) {
if (sigismember(&act.sa_mask, i)) {
! if (_thread_sigact[i - 1].sa_handler == SIG_DFL)
if (_thread_sys_sigaction(i,&act,NULL) != 0)
ret = -1;
}
}
! if (ret == 0) {
! /*
! * Save the wait signal mask. The wait signal
! * mask is independent of the threads signal mask
! * and requires separate storage.
! */
! _thread_run->data.sigwait = &act.sa_mask;
/* Wait for a signal: */
_thread_kern_sched_state(PS_SIGWAIT, __FILE__, __LINE__);
***************
*** 92,99 ****
/* Return the signal number to the caller: */
*sig = _thread_run->signo;
! /* Restore the signal mask: */
! _thread_run->sigmask = oset;
}
/* Restore the sigactions: */
--- 110,120 ----
/* Return the signal number to the caller: */
*sig = _thread_run->signo;
! /*
! * Probably unnecessary, but since it's in a union struct
! * we don't know how it could be used in the future.
! */
! _thread_run->data.sigwait = NULL;
}
/* Restore the sigactions: */
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*** sigwait.c.orig Tue Aug 25 08:35:16 1998
--- sigwait.c Sun Aug 30 22:08:29 1998
***************
*** 12,24 ****
* 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
--- 12,24 ----
* 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 Daniel M. Eischen.
* 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 DANIEL M. EISCHEN 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
***************
*** 31,51 ****
*
*/
#include <stdlib.h>
- #include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <string.h>
! static int sigcounts[NSIG + 1];
! static sigset_t wait_mask;
static void *
sigwaiter (void *arg)
{
int signo;
while (sigcounts[SIGINT] == 0) {
if (sigwait (&wait_mask, &signo) != 0) {
--- 31,63 ----
*
*/
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <pthread.h>
#include <signal.h>
+ #include <stdio.h>
#include <string.h>
! #if defined(__FreeBSD__)
! #include <pthread_np.h>
! #endif
!
! static int sigcounts[NSIG + 1];
! static sigset_t wait_mask;
! static pthread_mutex_t waiter_mutex;
!
static void *
sigwaiter (void *arg)
{
int signo;
+ sigset_t mask;
+
+ /* Block SIGHUP */
+ sigemptyset (&mask);
+ sigaddset (&mask, SIGHUP);
+ sigprocmask (SIG_BLOCK, &mask, NULL);
while (sigcounts[SIGINT] == 0) {
if (sigwait (&wait_mask, &signo) != 0) {
***************
*** 55,60 ****
--- 67,76 ----
}
sigcounts[signo]++;
printf ("Sigwait caught signal %d\n", signo);
+
+ /* Allow the main thread to prevent the sigwait. */
+ pthread_mutex_lock (&waiter_mutex);
+ pthread_mutex_unlock (&waiter_mutex);
}
pthread_exit (arg);
***************
*** 65,71 ****
static void
sighandler (int signo)
{
! printf ("Signal handler caught signal %d\n", signo);
if ((signo >= 0) && (signo <= NSIG))
sigcounts[signo]++;
--- 81,87 ----
static void
sighandler (int signo)
{
! printf (" -> Signal handler caught signal %d\n", signo);
if ((signo >= 0) && (signo <= NSIG))
sigcounts[signo]++;
***************
*** 92,97 ****
--- 108,114 ----
int main (int argc, char *argv[])
{
+ pthread_mutexattr_t mattr;
pthread_attr_t pattr;
pthread_t tid;
void * exit_status;
***************
*** 102,119 ****
/* Setupt our wait mask. */
sigemptyset (&wait_mask); /* Default action */
- sigaddset (&wait_mask, SIGINT); /* terminate */
sigaddset (&wait_mask, SIGHUP); /* terminate */
sigaddset (&wait_mask, SIGQUIT); /* create core image */
sigaddset (&wait_mask, SIGURG); /* ignore */
sigaddset (&wait_mask, SIGIO); /* ignore */
sigaddset (&wait_mask, SIGUSR1); /* terminate */
! /* Ignore signal SIGIO. */
sigemptyset (&act.sa_mask);
sigaddset (&act.sa_mask, SIGIO);
act.sa_handler = SIG_IGN;
act.sa_flags = 0;
sigaction (SIGIO, &act, NULL);
/* Install a signal handler for SIGURG */
--- 119,138 ----
/* Setupt our wait mask. */
sigemptyset (&wait_mask); /* Default action */
sigaddset (&wait_mask, SIGHUP); /* terminate */
+ sigaddset (&wait_mask, SIGINT); /* terminate */
sigaddset (&wait_mask, SIGQUIT); /* create core image */
sigaddset (&wait_mask, SIGURG); /* ignore */
sigaddset (&wait_mask, SIGIO); /* ignore */
sigaddset (&wait_mask, SIGUSR1); /* terminate */
! /* Ignore signals SIGHUP and SIGIO. */
sigemptyset (&act.sa_mask);
+ sigaddset (&act.sa_mask, SIGHUP);
sigaddset (&act.sa_mask, SIGIO);
act.sa_handler = SIG_IGN;
act.sa_flags = 0;
+ sigaction (SIGHUP, &act, NULL);
sigaction (SIGIO, &act, NULL);
/* Install a signal handler for SIGURG */
***************
*** 139,159 ****
}
/*
* Create the sigwaiter thread.
*/
if (pthread_create (&tid, &pattr, sigwaiter, NULL) != 0) {
! printf ("Unable to create thread, errno %d.\n", errno);
exit (1);
}
/*
* Verify that an ignored signal doesn't cause a wakeup.
* We don't have a handler installed for SIGIO.
*/
- printf ("Sending pthread_kill SIGIO.\n");
send_thread_signal (tid, SIGIO);
sleep (1);
- printf ("Sending kill SIGIO.\n");
send_process_signal (SIGIO);
sleep (1);
if (sigcounts[SIGIO] != 0)
--- 158,188 ----
}
/*
+ * Initialize and create a mutex.
+ */
+ if ((pthread_mutexattr_init (&mattr) != 0) ||
+ (pthread_mutex_init (&waiter_mutex, &mattr) != 0)) {
+ printf ("Unable to create waiter mutex.\n");
+ exit (1);
+ }
+
+ /*
* Create the sigwaiter thread.
*/
if (pthread_create (&tid, &pattr, sigwaiter, NULL) != 0) {
! printf ("Unable to create thread.\n");
exit (1);
}
+ #if defined(__FreeBSD__)
+ pthread_set_name_np (tid, "sigwaiter");
+ #endif
/*
* Verify that an ignored signal doesn't cause a wakeup.
* We don't have a handler installed for SIGIO.
*/
send_thread_signal (tid, SIGIO);
sleep (1);
send_process_signal (SIGIO);
sleep (1);
if (sigcounts[SIGIO] != 0)
***************
*** 180,185 ****
--- 209,283 ----
sleep (1);
if (sigcounts[SIGUSR1] != 2)
printf ("FAIL: sigwait doesn't wake up for SIGUSR1.\n");
+
+ /*
+ * Verify that if we install a signal handler for a previously
+ * ignored signal, an occurrence of this signal will release
+ * the (already waiting) sigwait.
+ */
+
+ /* Install a signal handler for SIGHUP. */
+ sigemptyset (&act.sa_mask);
+ sigaddset (&act.sa_mask, SIGHUP);
+ act.sa_handler = sighandler;
+ act.sa_flags = SA_RESTART;
+ sigaction (SIGHUP, &act, NULL);
+
+ /* Sending SIGHUP should release the sigwait. */
+ send_process_signal (SIGHUP);
+ sleep (1);
+ send_thread_signal (tid, SIGHUP);
+ sleep (1);
+ if (sigcounts[SIGHUP] != 2)
+ printf ("FAIL: sigwait doesn't wake up for SIGHUP.\n");
+
+ /*
+ * Verify that a pending signal in the waiters mask will
+ * cause sigwait to return the pending signal. We do this
+ * by taking the waiters mutex and signaling the waiter to
+ * release him from the sigwait. The waiter will block
+ * on taking the mutex, and we can then send the waiter a
+ * signal which should be added to his pending signals.
+ * The next time the waiter does a sigwait, he should
+ * return with the pending signal.
+ */
+ sigcounts[SIGHUP] = 0;
+ pthread_mutex_lock (&waiter_mutex);
+ /* Release the waiter from sigwait. */
+ send_process_signal (SIGHUP);
+ sleep (1);
+ if (sigcounts[SIGHUP] != 1)
+ printf ("FAIL: sigwait doesn't wake up for SIGHUP.\n");
+ /*
+ * Add SIGHUP to all threads pending signals. Since there is
+ * a signal handler installed for SIGHUP and this signal is
+ * blocked from the waiter thread and unblocked in the main
+ * thread, the signal handler should be called once for SIGHUP.
+ */
+ send_process_signal (SIGHUP);
+ /* Release the waiter thread and allow him to run. */
+ pthread_mutex_unlock (&waiter_mutex);
+ sleep (1);
+ if (sigcounts[SIGHUP] != 3)
+ printf ("FAIL: sigwait doesn't return for pending SIGHUP.\n");
+
+ /*
+ * Repeat the above test using pthread_kill and SIGUSR1
+ */
+ sigcounts[SIGUSR1] = 0;
+ pthread_mutex_lock (&waiter_mutex);
+ /* Release the waiter from sigwait. */
+ send_thread_signal (tid, SIGUSR1);
+ sleep (1);
+ if (sigcounts[SIGUSR1] != 1)
+ printf ("FAIL: sigwait doesn't wake up for SIGUSR1.\n");
+ /* Add SIGHUP to the waiters pending signals. */
+ send_thread_signal (tid, SIGUSR1);
+ /* Release the waiter thread and allow him to run. */
+ pthread_mutex_unlock (&waiter_mutex);
+ sleep (1);
+ if (sigcounts[SIGUSR1] != 2)
+ printf ("FAIL: sigwait doesn't return for pending SIGUSR1.\n");
/*
* Verify that we can still kill the process for a signal
--------------446B9B3D2781E494167EB0E7
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/*
* Copyright (c) 1998 Daniel M. Eischen <eischen@vigrid.com>
* 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 Daniel M. Eischen.
* 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 DANIEL M. EISCHEN 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 <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#if defined(__FreeBSD__)
#include <pthread_np.h>
#endif
static int sigcounts[NSIG + 1];
static int sigfifo[NSIG + 1];
static int fifo_depth = 0;
static sigset_t suspender_mask;
static pthread_t suspender_tid;
static void *
sigsuspender (void *arg)
{
int save_count, status, i;
sigset_t run_mask;
/* Run with all signals blocked. */
sigfillset (&run_mask);
sigprocmask (SIG_SETMASK, &run_mask, NULL);
/* Allow these signals to wake us up during a sigsuspend. */
sigfillset (&suspender_mask); /* Default action */
sigdelset (&suspender_mask, SIGINT); /* terminate */
sigdelset (&suspender_mask, SIGHUP); /* terminate */
sigdelset (&suspender_mask, SIGQUIT); /* create core image */
sigdelset (&suspender_mask, SIGURG); /* ignore */
sigdelset (&suspender_mask, SIGIO); /* ignore */
sigdelset (&suspender_mask, SIGUSR2); /* terminate */
while (sigcounts[SIGINT] == 0) {
save_count = sigcounts[SIGUSR2];
status = sigsuspend (&suspender_mask);
if ((status == 0) || (errno != EINTR)) {
printf ("Unable to suspend for signals, "
"errno %d, return value %d\n",
errno, status);
exit (1);
}
for (i = 0; i < fifo_depth; i++)
printf ("Sigsuspend woke up by signal %d\n",
sigfifo[i]);
fifo_depth = 0;
}
pthread_exit (arg);
return (NULL);
}
static void
sighandler (int signo)
{
sigset_t set;
pthread_t self;
if ((signo >= 0) && (signo <= NSIG))
sigcounts[signo]++;
/*
* If we are running on behalf of the suspender thread,
* ensure that we have the correct mask set.
*/
self = pthread_self ();
if (self == suspender_tid) {
sigfifo[fifo_depth] = signo;
fifo_depth++;
printf (" -> Suspender thread signal handler caught signal %d\n",
signo);
sigprocmask (SIG_SETMASK, NULL, &set);
if (set != suspender_mask)
printf (" >>> FAIL: sigsuspender signal handler running "
"with incorrect mask.\n");
}
else
printf (" -> Main thread signal handler caught signal %d\n",
signo);
}
static void
send_thread_signal (pthread_t tid, int signo)
{
if (pthread_kill (tid, signo) != 0) {
printf ("Unable to send thread signal, errno %d.\n", errno);
exit (1);
}
}
static void
send_process_signal (int signo)
{
if (kill (getpid (), signo) != 0) {
printf ("Unable to send process signal, errno %d.\n", errno);
exit (1);
}
}
int main (int argc, char *argv[])
{
pthread_attr_t pattr;
void * exit_status;
struct sigaction act;
sigset_t oldset;
sigset_t newset;
/* Initialize our signal counts. */
memset ((void *) sigcounts, 0, NSIG * sizeof (int));
/* Ignore signal SIGIO. */
sigemptyset (&act.sa_mask);
sigaddset (&act.sa_mask, SIGIO);
act.sa_handler = SIG_IGN;
act.sa_flags = 0;
sigaction (SIGIO, &act, NULL);
/* Install a signal handler for SIGURG. */
sigemptyset (&act.sa_mask);
sigaddset (&act.sa_mask, SIGURG);
act.sa_handler = sighandler;
act.sa_flags = SA_RESTART;
sigaction (SIGURG, &act, NULL);
/* Install a signal handler for SIGXCPU */
sigemptyset (&act.sa_mask);
sigaddset (&act.sa_mask, SIGXCPU);
sigaction (SIGXCPU, &act, NULL);
/* Get our current signal mask. */
sigprocmask (SIG_SETMASK, NULL, &oldset);
/* Mask out SIGUSR1 and SIGUSR2. */
newset = oldset;
sigaddset (&newset, SIGUSR1);
sigaddset (&newset, SIGUSR2);
sigprocmask (SIG_SETMASK, &newset, NULL);
/* Install a signal handler for SIGUSR1 and SIGUSR2 */
sigemptyset (&act.sa_mask);
sigaddset (&act.sa_mask, SIGUSR1);
sigaddset (&act.sa_mask, SIGUSR2);
act.sa_handler = sighandler;
act.sa_flags = SA_RESTART;
sigaction (SIGUSR1, &act, NULL);
sigaction (SIGUSR2, &act, NULL);
/*
* Initialize the thread attribute.
*/
if ((pthread_attr_init (&pattr) != 0) ||
(pthread_attr_setdetachstate (&pattr,
PTHREAD_CREATE_JOINABLE) != 0)) {
printf ("Unable to initialize thread attributes.\n");
exit (1);
}
/*
* Create the sigsuspender thread.
*/
if (pthread_create (&suspender_tid, &pattr, sigsuspender, NULL) != 0) {
printf ("Unable to create thread, errno %d.\n", errno);
exit (1);
}
#if defined(__FreeBSD__)
pthread_set_name_np (suspender_tid, "sigsuspender");
#endif
/*
* Verify that an ignored signal doesn't cause a wakeup.
* We don't have a handler installed for SIGIO.
*/
send_thread_signal (suspender_tid, SIGIO);
sleep (1);
send_process_signal (SIGIO);
sleep (1);
if (sigcounts[SIGIO] != 0)
printf ("FAIL: sigsuspend wakes up for ignored signal "
"SIGIO.\n");
/*
* Verify that a signal with a default action of ignore, for
* which we have a signal handler installed, will release a
* sigsuspend.
*/
send_thread_signal (suspender_tid, SIGURG);
sleep (1);
send_process_signal (SIGURG);
sleep (1);
if (sigcounts[SIGURG] != 3)
printf ("FAIL: sigsuspend doesn't wake up for SIGURG.\n");
/*
* Verify that a SIGUSR2 signal will release a sigsuspended
* thread.
*/
send_thread_signal (suspender_tid, SIGUSR2);
sleep (1);
send_process_signal (SIGUSR2);
sleep (1);
if (sigcounts[SIGUSR2] != 2)
printf ("FAIL: sigsuspend doesn't wake up for SIGUSR2.\n");
/*
* Verify that a signal, blocked in both the main and
* sigsuspender threads, does not cause the signal handler
* to be called.
*/
send_thread_signal (suspender_tid, SIGUSR1);
sleep (1);
send_process_signal (SIGUSR1);
sleep (1);
if (sigcounts[SIGUSR1] != 0)
printf ("FAIL: signal hander called for SIGUSR1.\n");
/*
* Verify that we can still kill the process for a signal
* not being waited on by sigwait.
*/
send_process_signal (SIGPIPE);
printf ("FAIL: SIGPIPE did not terminate process.\n");
/*
* Wait for the thread to finish.
*/
pthread_join (suspender_tid, &exit_status);
return (0);
}
--------------446B9B3D2781E494167EB0E7--
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