02292f131a
o The polling mechanism for I/O readiness was changed from
select() to poll(). In additon, a wrapped version of poll()
is now provided.
o The wrapped select routine now converts each fd_set to a
poll array so that the thread scheduler doesn't have to
perform a bitwise search for selected fds each time file
descriptors are polled for I/O readiness.
o The thread scheduler was modified to use a new queue (_workq)
for threads that need work. Threads waiting for I/O readiness
and spinblocks are added to the work queue in addition to the
waiting queue. This reduces the time spent forming/searching
the array of file descriptors being polled.
o The waiting queue (_waitingq) is now maintained in order of
thread wakeup time. This allows the thread scheduler to
find the nearest wakeup time by looking at the first thread
in the queue instead of searching the entire queue.
o Removed file descriptor locking for select/poll routines. An
application should not rely on the threads library for providing
this locking; if necessary, the application should use mutexes
to protect selecting/polling of file descriptors.
o Retrieve and use the kernel clock rate/resolution at startup
instead of hardcoding the clock resolution to 10 msec (tested
with kernel running at 1000 HZ).
o All queues have been changed to use queue.h macros. These
include the queues of all threads, dead threads, and threads
waiting for file descriptor locks.
o Added reinitialization of the GC mutex and condition variable
after a fork. Also prevented reallocation of the ready queue
after a fork.
o Prevented the wrapped close routine from closing the thread
kernel pipes.
o Initialized file descriptor table for stdio entries at thread
init.
o Provided additional flags to indicate to what queues threads
belong.
o Moved TAILQ initialization for statically allocated mutex and
condition variables to after the spinlock.
o Added dispatching of signals to pthread_kill. Removing the
dispatching of signals from thread activation broke sigsuspend
when pthread_kill was used to send a signal to a thread.
o Temporarily set the state of a thread to PS_SUSPENDED when it
is first created and placed in the list of threads so that it
will not be accidentally scheduled before becoming a member
of one of the scheduling queues.
o Change the signal handler to queue signals to the thread kernel
pipe if the scheduling queues are protected. When scheduling
queues are unprotected, signals are then dequeued and handled.
o Ensured that all installed signal handlers block the scheduling
signal and that the scheduling signal handler blocks all
other signals. This ensures that the signal handler is only
interruptible for and by non-scheduling signals. An atomic
lock is used to decide which instance of the signal handler
will handle pending signals.
o Removed _lock_thread_list and _unlock_thread_list as they are
no longer used to protect the thread list.
o Added missing RCS IDs to modified files.
o Added checks for appropriate queue membership and activity when
adding, removing, and searching the scheduling queues. These
checks add very little overhead and are enabled when compiled
with _PTHREADS_INVARIANTS defined. Suggested and implemented
by Tor Egge with some modification by me.
o Close a race condition in uthread_close. (Tor Egge)
o Protect the scheduling queues while modifying them in
pthread_cond_signal and _thread_fd_unlock. (Tor Egge)
o Ensure that when a thread gets a mutex, the mutex is on that
threads list of owned mutexes. (Tor Egge)
o Set the kernel-in-scheduler flag in _thread_kern_sched_state
and _thread_kern_sched_state_unlock to prevent a scheduling
signal from calling the scheduler again. (Tor Egge)
o Don't use TAILQ_FOREACH macro while searching the waiting
queue for threads in a sigwait state, because a change of
state destroys the TAILQ link. It is actually safe to do
so, though, because once a sigwaiting thread is found, the
loop ends and the function returns. (Tor Egge)
o When dispatching signals to threads, make the thread inherit
the signal deferral flag of the currently running thread.
(Tor Egge)
Submitted by: Daniel Eischen <eischen@vigrid.com> and
Tor Egge <Tor.Egge@fast.no>
391 lines
10 KiB
C
391 lines
10 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 REGENTS 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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* $Id$
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*/
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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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/* Static variables: */
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static spinlock_t signal_lock = _SPINLOCK_INITIALIZER;
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unsigned int pending_sigs[NSIG];
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unsigned int handled_sigs[NSIG];
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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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}
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void
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_thread_sig_handler(int sig, int code, struct sigcontext * scp)
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{
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char c;
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int i;
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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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_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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signal_lock.access_lock = 0;
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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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_thread_sig_handle(i, scp);
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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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void
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_thread_sig_handle(int sig, struct sigcontext * scp)
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{
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int i;
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pthread_t pthread, pthread_next;
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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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/*
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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 process each thread in the waiting
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* list that is sigwait-ing on a signal. Since POSIX
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* doesn't specify which thread will get the signal
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* if there are multiple waiters, we'll give it to the
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* first one we find.
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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 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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* Do not attempt to deliver this signal
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* to other threads.
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*/
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return;
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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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/*
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* Enter a loop to process each thread in the linked
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* list:
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*/
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TAILQ_FOREACH(pthread, &_thread_list, tle) {
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pthread_t pthread_saved = _thread_run;
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/* Current thread inside critical region? */
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if (_thread_run->sig_defer_count > 0)
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pthread->sig_defer_count++;
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_thread_run = pthread;
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_thread_signal(pthread,sig);
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/*
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* Dispatch pending signals to the
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* running thread:
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*/
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_dispatch_signals();
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_thread_run = pthread_saved;
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/* Current thread inside critical region? */
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if (_thread_run->sig_defer_count > 0)
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pthread->sig_defer_count--;
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}
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}
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/* Returns nothing. */
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return;
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}
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/* Perform thread specific actions in response to a signal: */
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void
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_thread_signal(pthread_t pthread, int sig)
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{
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/*
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* Flag the signal as pending. It will be dispatched later.
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*/
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sigaddset(&pthread->sigpend,sig);
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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_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_SIGWAIT:
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case PS_SUSPENDED:
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/* Nothing to do here. */
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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 (sig != SIGCHLD ||
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_thread_sigact[sig - 1].sa_handler != SIG_DFL) {
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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 the signal is unblocked
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* and there is a handler installed for the signal.
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*/
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if (!sigismember(&pthread->sigmask, sig) &&
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_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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/* 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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int i;
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/*
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* Check if there are pending signals for the running
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* thread that aren't blocked:
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*/
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if ((_thread_run->sigpend & ~_thread_run->sigmask) != 0)
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/* Look for all possible pending signals: */
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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(&_thread_run->sigpend,i) &&
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!sigismember(&_thread_run->sigmask,i)) {
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/* Clear the pending signal: */
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sigdelset(&_thread_run->sigpend,i);
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/*
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* Dispatch the signal via the custom signal
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* handler:
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*/
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(*(_thread_sigact[i - 1].sa_handler))(i);
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}
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}
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#endif
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