freebsd-dev/lib/libpthread/thread/thr_sigwait.c
Daniel Eischen fd626336fd Add a method of yielding the current thread with the scheduler
lock held (_thr_sched_switch_unlocked()) and use this to avoid
dropping the scheduler lock and having the scheduler retake the
same lock again.

Add a better way of detecting if a low-level lock is in use.

When switching out a thread due to blocking in the UTS, don't
switch to the KSE's scheduler stack only to switch back to
another thread.  If possible switch to the new thread directly
from the old thread and avoid the overhead of the extra
context switch.

Check for pending signals on a thread when entering the scheduler
and add them to the threads signal frame.  This includes some
other minor signal fixes.

Most of this was a joint effor between davidxu and myself.

Reviewed by:	davidxu
Approved by:	re@ (blanket for libpthread)
2003-05-16 19:58:30 +00:00

176 lines
5.5 KiB
C

//depot/projects/kse/lib/libpthread/thread/thr_sigwait.c#1 - branch change 15154 (text+ko)
/*
* Copyright (c) 1997 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.
*
* $FreeBSD$
*/
#include <signal.h>
#include <sys/param.h>
#include <sys/signalvar.h>
#include <errno.h>
#include <pthread.h>
#include "thr_private.h"
__weak_reference(_sigwait, sigwait);
int
_sigwait(const sigset_t *set, int *sig)
{
struct pthread *curthread = _get_curthread();
int ret = 0;
int i;
sigset_t tempset, waitset;
struct sigaction act;
kse_critical_t crit;
_thr_enter_cancellation_point(curthread);
/*
* Specify the thread kernel signal handler.
*/
act.sa_handler = (void (*) ()) _thr_sig_handler;
act.sa_flags = SA_RESTART | SA_SIGINFO;
/* Ensure the signal handler cannot be interrupted by other signals: */
sigfillset(&act.sa_mask);
/*
* Initialize the set of signals that will be waited on:
*/
waitset = *set;
/* These signals can't be waited on. */
sigdelset(&waitset, SIGKILL);
sigdelset(&waitset, SIGSTOP);
/*
* Check to see if a pending signal is in the wait mask.
* This has to be atomic.
*/
tempset = curthread->sigpend;
crit = _kse_critical_enter();
KSE_LOCK_ACQUIRE(curthread->kse, &_thread_signal_lock);
SIGSETOR(tempset, _thr_proc_sigpending);
SIGSETAND(tempset, waitset);
if (SIGNOTEMPTY(tempset)) {
/* Enter a loop to find a pending signal: */
for (i = 1; i < NSIG; i++) {
if (sigismember (&tempset, i))
break;
}
/* Clear the pending signal: */
if (sigismember(&curthread->sigpend, i))
sigdelset(&curthread->sigpend, i);
else
sigdelset(&_thr_proc_sigpending, i);
KSE_LOCK_RELEASE(curthread->kse, &_thread_signal_lock);
_kse_critical_leave(crit);
_thr_leave_cancellation_point(curthread);
/* 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.
*/
sigemptyset(&tempset);
for (i = 1; i < NSIG; i++) {
if (sigismember(&waitset, i) &&
(_thread_sigact[i - 1].sa_handler == SIG_DFL)) {
_thread_dfl_count[i]++;
sigaddset(&tempset, i);
if (_thread_dfl_count[i] == 1) {
if (__sys_sigaction(i, &act, NULL) != 0)
ret = -1;
}
}
}
/* Done accessing _thread_dfl_count for now. */
KSE_LOCK_RELEASE(curthread->kse, &_thread_signal_lock);
_kse_critical_leave(crit);
if (ret == 0) {
/*
* Save the wait signal mask. The wait signal
* mask is independent of the threads signal mask
* and requires separate storage.
*/
curthread->data.sigwait = &waitset;
/* Wait for a signal: */
THR_LOCK_SWITCH(curthread);
THR_SET_STATE(curthread, PS_SIGWAIT);
_thr_sched_switch_unlocked(curthread);
/* Return the signal number to the caller: */
*sig = curthread->signo;
/*
* Probably unnecessary, but since it's in a union struct
* we don't know how it could be used in the future.
*/
curthread->data.sigwait = NULL;
}
/*
* Relock the array of SIG_DFL wait counts.
*/
crit = _kse_critical_enter();
KSE_LOCK_ACQUIRE(curthread->kse, &_thread_signal_lock);
/* Restore the sigactions: */
act.sa_handler = SIG_DFL;
for (i = 1; i < NSIG; i++) {
if (sigismember(&tempset, i)) {
_thread_dfl_count[i]--;
if ((_thread_sigact[i - 1].sa_handler == SIG_DFL) &&
(_thread_dfl_count[i] == 0)) {
if (__sys_sigaction(i, &act, NULL) != 0)
ret = -1;
}
}
}
/* Done accessing _thread_dfl_count. */
KSE_LOCK_RELEASE(curthread->kse, &_thread_signal_lock);
_kse_critical_leave(crit);
_thr_leave_cancellation_point(curthread);
/* Return the completion status: */
return (ret);
}