lib/libc_r/uthread/uthread_sig.c

   1 /*
   2  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by John Birrell.
  16  * 4. Neither the name of the author nor the names of any co-contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * $Id: uthread_sig.c,v 1.17 1999/06/20 08:28:44 jb Exp $
  33  */
  34 #include <signal.h>
  35 #include <fcntl.h>
  36 #include <unistd.h>
  37 #include <errno.h>
  38 #ifdef _THREAD_SAFE
  39 #include <pthread.h>
  40 #include "pthread_private.h"
  41
  42 /* Static variables: */
  43 static spinlock_t       signal_lock = _SPINLOCK_INITIALIZER;
  44 unsigned int            pending_sigs[NSIG];
  45 unsigned int            handled_sigs[NSIG];
  46 int                     volatile check_pending = 0;
  47
  48 /* Initialize signal handling facility: */
  49 void
  50 _thread_sig_init(void)
  51 {
  52         int i;
  53
  54         /* Clear pending and handled signal counts: */
  55         for (i = 1; i < NSIG; i++) {
  56                 pending_sigs[i - 1] = 0;
  57                 handled_sigs[i - 1] = 0;
  58         }
  59
  60         /* Clear the lock: */
  61         signal_lock.access_lock = 0;
  62 }
  63
  64 void
  65 _thread_sig_handler(int sig, int code, struct sigcontext * scp)
  66 {
  67         char    c;
  68         int     i;
  69
  70         /* Check if an interval timer signal: */
  71         if (sig == _SCHED_SIGNAL) {
  72                 if (_thread_kern_in_sched != 0) {
  73                         /*
  74                          * The scheduler is already running; ignore this
  75                          * signal.
  76                          */
  77                 }
  78                 /*
  79                  * Check if the scheduler interrupt has come when
  80                  * the currently running thread has deferred thread
  81                  * signals.
  82                  */
  83                 else if (_thread_run->sig_defer_count > 0)
  84                         _thread_run->yield_on_sig_undefer = 1;
  85
  86                 else {
  87                         /*
  88                          * Schedule the next thread. This function is not
  89                          * expected to return because it will do a longjmp
  90                          * instead.
  91                          */
  92                         _thread_kern_sched(scp);
  93
  94                         /*
  95                          * This point should not be reached, so abort the
  96                          * process:
  97                          */
  98                         PANIC("Returned to signal function from scheduler");
  99                 }
 100         }
 101         /*
 102          * Check if the kernel has been interrupted while the scheduler
 103          * is accessing the scheduling queues or if there is a currently
 104          * running thread that has deferred signals.
 105          */
 106         else if ((_queue_signals != 0) || ((_thread_kern_in_sched == 0) &&
 107             (_thread_run->sig_defer_count > 0))) {
 108                 /* Cast the signal number to a character variable: */
 109                 c = sig;
 110
 111                 /*
 112                  * Write the signal number to the kernel pipe so that it will
 113                  * be ready to read when this signal handler returns.
 114                  */
 115                 _thread_sys_write(_thread_kern_pipe[1], &c, 1);
 116
 117                 /* Indicate that there are queued signals in the pipe. */
 118                 _sigq_check_reqd = 1;
 119         }
 120         else {
 121                 if (_atomic_lock(&signal_lock.access_lock)) {
 122                         /* There is another signal handler running: */
 123                         pending_sigs[sig - 1]++;
 124                         check_pending = 1;
 125                 }
 126                 else {
 127                         /* It's safe to handle the signal now. */
 128                         _thread_sig_handle(sig, scp);
 129
 130                         /* Reset the pending and handled count back to 0: */
 131                         pending_sigs[sig - 1] = 0;
 132                         handled_sigs[sig - 1] = 0;
 133
 134                         signal_lock.access_lock = 0;
 135                 }
 136
 137                 /* Enter a loop to process pending signals: */
 138                 while ((check_pending != 0) &&
 139                     (_atomic_lock(&signal_lock.access_lock) == 0)) {
 140                         check_pending = 0;
 141                         for (i = 1; i < NSIG; i++) {
 142                                 if (pending_sigs[i - 1] > handled_sigs[i - 1])
 143                                         _thread_sig_handle(i, scp);
 144                         }
 145                         signal_lock.access_lock = 0;
 146                 }
 147         }
 148 }
 149
 150 void
 151 _thread_sig_handle(int sig, struct sigcontext * scp)
 152 {
 153         int             i;
 154         pthread_t       pthread, pthread_next;
 155
 156         /* Check if the signal requires a dump of thread information: */
 157         if (sig == SIGINFO)
 158                 /* Dump thread information to file: */
 159                 _thread_dump_info();
 160
 161         /* Check if an interval timer signal: */
 162         else if (sig == _SCHED_SIGNAL) {
 163                 /*
 164                  * This shouldn't ever occur (should this panic?).
 165                  */
 166         } else {
 167                 /* Check if a child has terminated: */
 168                 if (sig == SIGCHLD) {
 169                         /*
 170                          * Go through the file list and set all files
 171                          * to non-blocking again in case the child
 172                          * set some of them to block. Sigh.
 173                          */
 174                         for (i = 0; i < _thread_dtablesize; i++) {
 175                                 /* Check if this file is used: */
 176                                 if (_thread_fd_table[i] != NULL) {
 177                                         /*
 178                                          * Set the file descriptor to
 179                                          * non-blocking:
 180                                          */
 181                                         _thread_sys_fcntl(i, F_SETFL,
 182                                             _thread_fd_table[i]->flags |
 183                                             O_NONBLOCK);
 184                                 }
 185                         }
 186                 }
 187
 188                 /*
 189                  * POSIX says that pending SIGCONT signals are
 190                  * discarded when one of these signals occurs.
 191                  */
 192                 if (sig == SIGTSTP || sig == SIGTTIN || sig == SIGTTOU) {
 193                         /*
 194                          * Enter a loop to discard pending SIGCONT
 195                          * signals:
 196                          */
 197                         TAILQ_FOREACH(pthread, &_thread_list, tle) {
 198                                 sigdelset(&pthread->sigpend,SIGCONT);
 199                         }
 200                 }
 201
 202                 /*
 203                  * Enter a loop to process each thread in the waiting
 204                  * list that is sigwait-ing on a signal.  Since POSIX
 205                  * doesn't specify which thread will get the signal
 206                  * if there are multiple waiters, we'll give it to the
 207                  * first one we find.
 208                  */
 209                 for (pthread = TAILQ_FIRST(&_waitingq);
 210                     pthread != NULL; pthread = pthread_next) {
 211                         /*
 212                          * Grab the next thread before possibly destroying
 213                          * the link entry.
 214                          */
 215                         pthread_next = TAILQ_NEXT(pthread, pqe);
 216
 217                         if ((pthread->state == PS_SIGWAIT) &&
 218                             sigismember(pthread->data.sigwait, sig)) {
 219                                 /* Change the state of the thread to run: */
 220                                 PTHREAD_NEW_STATE(pthread,PS_RUNNING);
 221
 222                                 /* Return the signal number: */
 223                                 pthread->signo = sig;
 224
 225                                 /*
 226                                  * Do not attempt to deliver this signal
 227                                  * to other threads.
 228                                  */
 229                                 return;
 230                         }
 231                 }
 232
 233                 /* Check if the signal is not being ignored: */
 234                 if (_thread_sigact[sig - 1].sa_handler != SIG_IGN)
 235                         /*
 236                          * Enter a loop to process each thread in the linked
 237                          * list:
 238                          */
 239                         TAILQ_FOREACH(pthread, &_thread_list, tle) {
 240                                 pthread_t pthread_saved = _thread_run;
 241
 242                                 /* Current thread inside critical region? */
 243                                 if (_thread_run->sig_defer_count > 0)
 244                                         pthread->sig_defer_count++;
 245
 246                                 _thread_run = pthread;
 247                                 _thread_signal(pthread,sig);
 248
 249                                 /*
 250                                  * Dispatch pending signals to the
 251                                  * running thread:
 252                                  */
 253                                 _dispatch_signals();
 254                                 _thread_run = pthread_saved;
 255
 256                                 /* Current thread inside critical region? */
 257                                 if (_thread_run->sig_defer_count > 0)
 258                                         pthread->sig_defer_count--;
 259                         }
 260         }
 261
 262         /* Returns nothing. */
 263         return;
 264 }
 265
 266 /* Perform thread specific actions in response to a signal: */
 267 void
 268 _thread_signal(pthread_t pthread, int sig)
 269 {
 270         /*
 271          * Flag the signal as pending. It will be dispatched later.
 272          */
 273         sigaddset(&pthread->sigpend,sig);
 274
 275         /*
 276          * Process according to thread state:
 277          */
 278         switch (pthread->state) {
 279         /*
 280          * States which do not change when a signal is trapped:
 281          */
 282         case PS_COND_WAIT:
 283         case PS_DEAD:
 284         case PS_FDLR_WAIT:
 285         case PS_FDLW_WAIT:
 286         case PS_FILE_WAIT:
 287         case PS_JOIN:
 288         case PS_MUTEX_WAIT:
 289         case PS_RUNNING:
 290         case PS_STATE_MAX:
 291         case PS_SIGTHREAD:
 292         case PS_SIGWAIT:
 293         case PS_SUSPENDED:
 294                 /* Nothing to do here. */
 295                 break;
 296
 297         /*
 298          * The wait state is a special case due to the handling of
 299          * SIGCHLD signals.
 300          */
 301         case PS_WAIT_WAIT:
 302                 /*
 303                  * Check for signals other than the death of a child
 304                  * process:
 305                  */
 306                 if (sig != SIGCHLD)
 307                         /* Flag the operation as interrupted: */
 308                         pthread->interrupted = 1;
 309
 310                 /* Change the state of the thread to run: */
 311                 PTHREAD_NEW_STATE(pthread,PS_RUNNING);
 312
 313                 /* Return the signal number: */
 314                 pthread->signo = sig;
 315                 break;
 316
 317         /*
 318          * States that are interrupted by the occurrence of a signal
 319          * other than the scheduling alarm:
 320          */
 321         case PS_FDR_WAIT:
 322         case PS_FDW_WAIT:
 323         case PS_POLL_WAIT:
 324         case PS_SLEEP_WAIT:
 325         case PS_SELECT_WAIT:
 326                 if (sig != SIGCHLD ||
 327                     _thread_sigact[sig - 1].sa_handler != SIG_DFL) {
 328                         /* Flag the operation as interrupted: */
 329                         pthread->interrupted = 1;
 330
 331                         if (pthread->flags & PTHREAD_FLAGS_IN_WORKQ)
 332                                 PTHREAD_WORKQ_REMOVE(pthread);
 333
 334                         /* Change the state of the thread to run: */
 335                         PTHREAD_NEW_STATE(pthread,PS_RUNNING);
 336
 337                         /* Return the signal number: */
 338                         pthread->signo = sig;
 339                 }
 340                 break;
 341
 342         case PS_SIGSUSPEND:
 343                 /*
 344                  * Only wake up the thread if the signal is unblocked
 345                  * and there is a handler installed for the signal.
 346                  */
 347                 if (!sigismember(&pthread->sigmask, sig) &&
 348                     _thread_sigact[sig - 1].sa_handler != SIG_DFL) {
 349                         /* Change the state of the thread to run: */
 350                         PTHREAD_NEW_STATE(pthread,PS_RUNNING);
 351
 352                         /* Return the signal number: */
 353                         pthread->signo = sig;
 354                 }
 355                 break;
 356         }
 357 }
 358
 359 /* Dispatch pending signals to the running thread: */
 360 void
 361 _dispatch_signals()
 362 {
 363         int i;
 364
 365         /*
 366          * Check if there are pending signals for the running
 367          * thread that aren't blocked:
 368          */
 369         if ((_thread_run->sigpend & ~_thread_run->sigmask) != 0)
 370                 /* Look for all possible pending signals: */
 371                 for (i = 1; i < NSIG; i++)
 372                         /*
 373                          * Check that a custom handler is installed
 374                          * and if the signal is not blocked:
 375                          */
 376                         if (_thread_sigact[i - 1].sa_handler != SIG_DFL &&
 377                             _thread_sigact[i - 1].sa_handler != SIG_IGN &&
 378                             sigismember(&_thread_run->sigpend,i) &&
 379                             !sigismember(&_thread_run->sigmask,i)) {
 380                                 /* Clear the pending signal: */
 381                                 sigdelset(&_thread_run->sigpend,i);
 382
 383                                 /*
 384                                  * Dispatch the signal via the custom signal
 385                                  * handler:
 386                                  */
 387                                 (*(_thread_sigact[i - 1].sa_handler))(i);
 388                         }
 389 }
 390 #endif