freebsd-dev/lib/libpthread/thread/thr_sig.c
Daniel Eischen 1d013a86ed Fix pthread_suspend_np/pthread_resume_np. For the record, suspending a
thread waiting on an event (I/O, condvar, etc) will, when resumed using
pthread_resume_np, return with EINTR.  For example, suspending and resuming
a thread blocked on read() will not requeue the thread for the read, but
will return -1 with errno = EINTR.  If the suspended thread is in a critical
region, the thread is suspended as soon as it leaves the critical region.

Fix a bogon in pthread_kill() where a signal was being delivered twice
to threads waiting in sigwait().

Reported by (suspend/resume bug):	jdp
Reviewed by:	jasone
2000-03-15 13:59:27 +00:00

762 lines
20 KiB
C

/*
* 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.
*
* $FreeBSD$
*/
#include <sys/param.h>
#include <sys/types.h>
#include <sys/signalvar.h>
#include <signal.h>
#include <fcntl.h>
#include <unistd.h>
#include <setjmp.h>
#include <errno.h>
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"
/* Prototypes: */
static void thread_sig_check_state(pthread_t pthread, int sig);
static void thread_sig_finish_longjmp(void *arg);
static void handle_state_change(pthread_t pthread);
/* Static variables: */
static spinlock_t signal_lock = _SPINLOCK_INITIALIZER;
static unsigned int pending_sigs[NSIG];
static unsigned int handled_sigs[NSIG];
static int volatile check_pending = 0;
static int volatile check_waiting = 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;
/* Clear the process pending signals: */
sigemptyset(&_process_sigpending);
}
void
_thread_sig_handler(int sig, int code, ucontext_t * scp)
{
pthread_t pthread, pthread_next;
int i;
char c;
/* Check if an interval timer signal: */
if (sig == _SCHED_SIGNAL) {
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 (_thread_run->sig_defer_count > 0)
_thread_run->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);
/*
* This point should not be reached, so abort the
* process:
*/
PANIC("Returned to signal function from scheduler");
}
}
/*
* 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) &&
(_thread_run->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. */
pthread = _thread_sig_handle(sig, scp);
/* Reset the pending and handled count back to 0: */
pending_sigs[sig - 1] = 0;
handled_sigs[sig - 1] = 0;
if (pthread == NULL)
signal_lock.access_lock = 0;
else {
sigaddset(&pthread->sigmask, sig);
/*
* Make sure not to deliver the same signal to
* the thread twice. sigpend is potentially
* modified by the call chain
* _thread_sig_handle() -->
* thread_sig_check_state(), which can happen
* just above.
*/
if (sigismember(&pthread->sigpend, sig))
sigdelset(&pthread->sigpend, sig);
signal_lock.access_lock = 0;
_thread_sig_deliver(pthread, sig);
sigdelset(&pthread->sigmask, sig);
}
}
/* 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]) {
pending_sigs[i - 1] = handled_sigs[i - 1];
pthread = _thread_sig_handle(i, scp);
if (pthread != NULL) {
sigaddset(&pthread->sigmask, i);
/* Save the old state: */
pthread->oldstate = pthread->state;
signal_lock.access_lock = 0;
_thread_sig_deliver(pthread, i);
sigdelset(&pthread->sigmask, i);
if (_atomic_lock(&signal_lock.access_lock)) {
check_pending = 1;
/*
* Have the lock holder take care
* of any state changes:
*/
if (pthread->state != pthread->oldstate)
check_waiting = 1;
return;
}
if (pthread->state != pthread->oldstate)
handle_state_change(pthread);
}
}
}
while (check_waiting != 0) {
check_waiting = 0;
/*
* Enter a loop to wake up all threads waiting
* for a process to complete:
*/
for (pthread = TAILQ_FIRST(&_waitingq);
pthread != NULL; pthread = pthread_next) {
pthread_next = TAILQ_NEXT(pthread, pqe);
if (pthread->state == PS_RUNNING)
handle_state_change(pthread);
}
}
/* Release the lock: */
signal_lock.access_lock = 0;
}
/*
* Check to see if the current thread performed a
* [sig|_]longjmp() out of a signal handler.
*/
if ((_thread_run->jmpflags & (JMPFLAGS_LONGJMP |
JMPFLAGS__LONGJMP)) != 0) {
_thread_run->jmpflags = JMPFLAGS_NONE;
__longjmp(_thread_run->nested_jmp.jmp,
_thread_run->longjmp_val);
} else if ((_thread_run->jmpflags & JMPFLAGS_SIGLONGJMP) != 0) {
_thread_run->jmpflags = JMPFLAGS_NONE;
__siglongjmp(_thread_run->nested_jmp.sigjmp,
_thread_run->longjmp_val);
}
}
}
pthread_t
_thread_sig_handle(int sig, ucontext_t * scp)
{
int i, handler_installed;
pthread_t pthread, pthread_next;
pthread_t suspended_thread, signaled_thread;
/* 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);
}
}
/*
* Enter a loop to wake up all threads waiting
* for a process to complete:
*/
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 this thread is waiting for a child
* process to complete, wake it up:
*/
if (pthread->state == PS_WAIT_WAIT) {
/* Make the thread runnable: */
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
/* Return the signal number: */
pthread->signo = sig;
}
}
}
/*
* 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 look for threads that have the signal
* unmasked. POSIX specifies that a thread in a sigwait
* will get the signal over any other threads. Second
* preference will be threads in in a sigsuspend. If
* none of the above, then the signal is delivered to the
* first thread we find. Note that if a custom handler
* is not installed, the signal only affects threads in
* sigwait.
*/
suspended_thread = NULL;
signaled_thread = NULL;
if ((_thread_sigact[sig - 1].sa_handler == SIG_IGN) ||
(_thread_sigact[sig - 1].sa_handler == SIG_DFL))
handler_installed = 0;
else
handler_installed = 1;
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;
/*
* POSIX doesn't doesn't specify which thread
* will get the signal if there are multiple
* waiters, so we give it to the first thread
* we find.
*
* Do not attempt to deliver this signal
* to other threads.
*/
return (NULL);
}
else if ((handler_installed != 0) &&
!sigismember(&pthread->sigmask, sig)) {
if (pthread->state == PS_SIGSUSPEND) {
if (suspended_thread == NULL)
suspended_thread = pthread;
} else if (signaled_thread == NULL)
signaled_thread = pthread;
}
}
/*
* Only perform wakeups and signal delivery if there is a
* custom handler installed:
*/
if (handler_installed != 0) {
/*
* If we didn't find a thread in the waiting queue,
* check the all threads queue:
*/
if (suspended_thread == NULL &&
signaled_thread == NULL) {
/*
* Enter a loop to look for other threads
* capable of receiving the signal:
*/
TAILQ_FOREACH(pthread, &_thread_list, tle) {
if (!sigismember(&pthread->sigmask,
sig)) {
signaled_thread = pthread;
break;
}
}
}
if (suspended_thread == NULL &&
signaled_thread == NULL)
/*
* Add it to the set of signals pending
* on the process:
*/
sigaddset(&_process_sigpending, sig);
else {
/*
* We only deliver the signal to one thread;
* give preference to the suspended thread:
*/
if (suspended_thread != NULL)
pthread = suspended_thread;
else
pthread = signaled_thread;
/*
* Perform any state changes due to signal
* arrival:
*/
thread_sig_check_state(pthread, sig);
return (pthread);
}
}
}
/* Returns nothing. */
return (NULL);
}
static void
thread_sig_finish_longjmp(void *arg)
{
/*
* Check to see if the current thread performed a [_]longjmp() out of a
* signal handler.
*/
if ((_thread_run->jmpflags & (JMPFLAGS_LONGJMP | JMPFLAGS__LONGJMP))
!= 0) {
_thread_run->jmpflags = JMPFLAGS_NONE;
_thread_run->continuation = NULL;
__longjmp(_thread_run->nested_jmp.jmp,
_thread_run->longjmp_val);
}
/*
* Check to see if the current thread performed a siglongjmp
* out of a signal handler:
*/
else if ((_thread_run->jmpflags & JMPFLAGS_SIGLONGJMP) != 0) {
_thread_run->jmpflags = JMPFLAGS_NONE;
_thread_run->continuation = NULL;
__siglongjmp(_thread_run->nested_jmp.sigjmp,
_thread_run->longjmp_val);
}
}
static void
handle_state_change(pthread_t pthread)
{
/*
* We should only need to handle threads whose state was
* changed to running:
*/
if (pthread->state == PS_RUNNING) {
switch (pthread->oldstate) {
/*
* States which do not change when a signal is trapped:
*/
case PS_DEAD:
case PS_DEADLOCK:
case PS_RUNNING:
case PS_SIGTHREAD:
case PS_STATE_MAX:
case PS_SUSPENDED:
break;
/*
* States which need to return to critical sections
* before they can switch contexts:
*/
case PS_COND_WAIT:
case PS_FDLR_WAIT:
case PS_FDLW_WAIT:
case PS_FILE_WAIT:
case PS_JOIN:
case PS_MUTEX_WAIT:
/* Indicate that the thread was interrupted: */
pthread->interrupted = 1;
/*
* Defer the [sig|_]longjmp until leaving the critical
* region:
*/
pthread->jmpflags |= JMPFLAGS_DEFERRED;
/* Set the continuation routine: */
pthread->continuation = thread_sig_finish_longjmp;
/* FALLTHROUGH */
case PS_FDR_WAIT:
case PS_FDW_WAIT:
case PS_POLL_WAIT:
case PS_SELECT_WAIT:
case PS_SIGSUSPEND:
case PS_SIGWAIT:
case PS_SLEEP_WAIT:
case PS_SPINBLOCK:
case PS_WAIT_WAIT:
if ((pthread->flags & PTHREAD_FLAGS_IN_WAITQ) != 0) {
PTHREAD_WAITQ_REMOVE(pthread);
if (pthread->flags & PTHREAD_FLAGS_IN_WORKQ)
PTHREAD_WORKQ_REMOVE(pthread);
}
break;
}
if ((pthread->flags & PTHREAD_FLAGS_IN_PRIOQ) == 0)
PTHREAD_PRIOQ_INSERT_TAIL(pthread);
}
}
/* Perform thread specific actions in response to a signal: */
static void
thread_sig_check_state(pthread_t pthread, int sig)
{
/*
* 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_DEADLOCK:
case PS_FILE_WAIT:
case PS_JOIN:
case PS_MUTEX_WAIT:
case PS_RUNNING:
case PS_STATE_MAX:
case PS_SIGTHREAD:
case PS_SPINBLOCK:
case PS_SUSPENDED:
/* 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;
/*
* 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_FDLR_WAIT:
case PS_FDLW_WAIT:
case PS_FDR_WAIT:
case PS_FDW_WAIT:
case PS_POLL_WAIT:
case PS_SLEEP_WAIT:
case PS_SELECT_WAIT:
if ((_thread_sigact[sig - 1].sa_flags & SA_RESTART) == 0) {
/* 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 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;
}
}
/* Send a signal to a specific thread (ala pthread_kill): */
void
_thread_sig_send(pthread_t pthread, int sig)
{
/*
* Check that the signal is not being ignored:
*/
if (_thread_sigact[sig - 1].sa_handler != SIG_IGN) {
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;
} else if (pthread->state != PS_SIGWAIT &&
!sigismember(&pthread->sigmask, sig)) {
/* Perform any state changes due to signal arrival: */
thread_sig_check_state(pthread, sig);
/* Increment the pending signal count. */
sigaddset(&pthread->sigpend,sig);
} else {
/* Increment the pending signal count. */
sigaddset(&pthread->sigpend,sig);
}
}
}
/* Dispatch pending signals to the running thread: */
void
_dispatch_signals()
{
sigset_t sigset;
int i;
/*
* Check if there are pending signals for the running
* thread or process that aren't blocked:
*/
sigset = _thread_run->sigpend;
SIGSETOR(sigset, _process_sigpending);
SIGSETNAND(sigset, _thread_run->sigmask);
if (SIGNOTEMPTY(sigset)) {
/*
* Enter a loop to calculate deliverable pending signals
* before actually delivering them. The pending signals
* must be removed from the pending signal sets before
* calling the signal handler because the handler may
* call library routines that again check for and deliver
* 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(&sigset, i)) {
if (sigismember(&_thread_run->sigpend,i))
/* Clear the thread pending signal: */
sigdelset(&_thread_run->sigpend,i);
else
/* Clear the process pending signal: */
sigdelset(&_process_sigpending,i);
}
else
/* Remove the signal if it can't be handled: */
sigdelset(&sigset, i);
}
/* Now deliver the signals: */
for (i = 1; i < NSIG; i++) {
if (sigismember(&sigset, i))
/* Deliver the signal to the running thread: */
_thread_sig_deliver(_thread_run, i);
}
}
}
/* Deliver a signal to a thread: */
void
_thread_sig_deliver(pthread_t pthread, int sig)
{
sigset_t mask;
pthread_t pthread_saved;
jmp_buf jb, *saved_sighandler_jmp_buf;
/*
* 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 thread's 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++;
/* Increment the number of nested signals being handled. */
pthread->signal_nest_level++;
/*
* The jump buffer is allocated off the stack and the current
* jump buffer is saved. If the signal handler tries to
* [sig|_]longjmp(), our version of [sig|_]longjmp() will copy
* the user supplied jump buffer into
* _thread_run->nested_jmp.[sig]jmp and _longjmp() back to here.
*/
saved_sighandler_jmp_buf = pthread->sighandler_jmp_buf;
pthread->sighandler_jmp_buf = &jb;
_thread_run = pthread;
if (_setjmp(jb) == 0) {
/*
* Dispatch the signal via the custom signal
* handler:
*/
(*(_thread_sigact[sig - 1].sa_handler))(sig);
}
_thread_run = pthread_saved;
pthread->sighandler_jmp_buf = saved_sighandler_jmp_buf;
/* Decrement the signal nest level. */
pthread->signal_nest_level--;
/* 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