linuxthreads/manager.c

   1 /* Linuxthreads - a simple clone()-based implementation of Posix        */
   2 /* threads for Linux.                                                   */
   3 /* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
   4 /*                                                                      */
   5 /* This program is free software; you can redistribute it and/or        */
   6 /* modify it under the terms of the GNU Library General Public License  */
   7 /* as published by the Free Software Foundation; either version 2       */
   8 /* of the License, or (at your option) any later version.               */
   9 /*                                                                      */
  10 /* This program is distributed in the hope that it will be useful,      */
  11 /* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
  12 /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
  13 /* GNU Library General Public License for more details.                 */
  14
  15 /* The "thread manager" thread: manages creation and termination of threads */
  16
  17 #include <errno.h>
  18 #include <sched.h>
  19 #include <stddef.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <unistd.h>
  24 #include <sys/poll.h>           /* for poll */
  25 #include <sys/mman.h>           /* for mmap */
  26 #include <sys/time.h>
  27 #include <sys/wait.h>           /* for waitpid macros */
  28 #include <linux/tasks.h>
  29
  30 #include "pthread.h"
  31 #include "internals.h"
  32 #include "spinlock.h"
  33 #include "restart.h"
  34 #include "semaphore.h"
  35
  36 /* Array of active threads. Entry 0 is reserved for the initial thread. */
  37 struct pthread_handle_struct __pthread_handles[PTHREAD_THREADS_MAX] =
  38 { { LOCK_INITIALIZER, &__pthread_initial_thread, 0}, /* All NULLs */ };
  39
  40 /* Indicate whether at least one thread has a user-defined stack (if 1),
  41    or if all threads have stacks supplied by LinuxThreads (if 0). */
  42 int __pthread_nonstandard_stacks = 0;
  43
  44 /* Number of active entries in __pthread_handles (used by gdb) */
  45 volatile int __pthread_handles_num = 1;
  46
  47 /* Whether to use debugger additional actions for thread creation
  48    (set to 1 by gdb) */
  49 volatile int __pthread_threads_debug = 0;
  50
  51 /* Mapping from stack segment to thread descriptor. */
  52 /* Stack segment numbers are also indices into the __pthread_handles array. */
  53 /* Stack segment number 0 is reserved for the initial thread. */
  54
  55 static inline pthread_descr thread_segment(int seg)
  56 {
  57   return (pthread_descr)(THREAD_STACK_START_ADDRESS - (seg - 1) * STACK_SIZE)
  58          - 1;
  59 }
  60
  61 /* Flag set in signal handler to record child termination */
  62
  63 static volatile int terminated_children = 0;
  64
  65 /* Flag set when the initial thread is blocked on pthread_exit waiting
  66    for all other threads to terminate */
  67
  68 static int main_thread_exiting = 0;
  69
  70 /* Counter used to generate unique thread identifier.
  71    Thread identifier is pthread_threads_counter + segment. */
  72
  73 static pthread_t pthread_threads_counter = 0;
  74
  75 /* Forward declarations */
  76
  77 static int pthread_handle_create(pthread_t *thread, const pthread_attr_t *attr,
  78                                  void * (*start_routine)(void *), void *arg,
  79                                  sigset_t *mask, int father_pid);
  80 static void pthread_handle_free(pthread_t th_id);
  81 static void pthread_handle_exit(pthread_descr issuing_thread, int exitcode);
  82 static void pthread_reap_children(void);
  83 static void pthread_kill_all_threads(int sig, int main_thread_also);
  84
  85 /* The server thread managing requests for thread creation and termination */
  86
  87 int __pthread_manager(void *arg)
  88 {
  89   int reqfd = (int)arg;
  90   struct pollfd ufd;
  91   sigset_t mask;
  92   int n;
  93   struct pthread_request request;
  94
  95   /* If we have special thread_self processing, initialize it.  */
  96 #ifdef INIT_THREAD_SELF
  97   INIT_THREAD_SELF(&__pthread_manager_thread);
  98 #endif
  99   /* Set the error variable.  */
 100   __pthread_manager_thread.p_errnop = &__pthread_manager_thread.p_errno;
 101   __pthread_manager_thread.p_h_errnop = &__pthread_manager_thread.p_h_errno;
 102   /* Block all signals except PTHREAD_SIG_RESTART, PTHREAD_SIG_CANCEL
 103      and SIGTRAP */
 104   sigfillset(&mask);
 105   sigdelset(&mask, PTHREAD_SIG_RESTART);
 106   sigdelset(&mask, PTHREAD_SIG_CANCEL); /* for debugging new threads */
 107   sigdelset(&mask, SIGTRAP);            /* for debugging purposes */
 108   sigprocmask(SIG_SETMASK, &mask, NULL);
 109   /* Raise our priority to match that of main thread */
 110   __pthread_manager_adjust_prio(__pthread_main_thread->p_priority);
 111   /* Synchronize debugging of the thread manager */
 112   n = __libc_read(reqfd, (char *)&request, sizeof(request));
 113   ASSERT(n == sizeof(request) && request.req_kind == REQ_DEBUG);
 114   ufd.fd = reqfd;
 115   ufd.events = POLLIN;
 116   /* Enter server loop */
 117   while(1) {
 118     n = __poll(&ufd, 1, 2000);
 119
 120     /* Check for termination of the main thread */
 121     if (getppid() == 1) {
 122       pthread_kill_all_threads(SIGKILL, 0);
 123       _exit(0);
 124     }
 125     /* Check for dead children */
 126     if (terminated_children) {
 127       terminated_children = 0;
 128       pthread_reap_children();
 129     }
 130     /* Read and execute request */
 131     if (n == 1 && (ufd.revents & POLLIN)) {
 132       n = __libc_read(reqfd, (char *)&request, sizeof(request));
 133       ASSERT(n == sizeof(request));
 134       switch(request.req_kind) {
 135       case REQ_CREATE:
 136         request.req_thread->p_retcode =
 137           pthread_handle_create((pthread_t *) &request.req_thread->p_retval,
 138                                 request.req_args.create.attr,
 139                                 request.req_args.create.fn,
 140                                 request.req_args.create.arg,
 141                                 &request.req_args.create.mask,
 142                                 request.req_thread->p_pid);
 143         restart(request.req_thread);
 144         break;
 145       case REQ_FREE:
 146         pthread_handle_free(request.req_args.free.thread_id);
 147         break;
 148       case REQ_PROCESS_EXIT:
 149         pthread_handle_exit(request.req_thread,
 150                             request.req_args.exit.code);
 151         break;
 152       case REQ_MAIN_THREAD_EXIT:
 153         main_thread_exiting = 1;
 154         if (__pthread_main_thread->p_nextlive == __pthread_main_thread) {
 155           restart(__pthread_main_thread);
 156           return 0;
 157         }
 158         break;
 159       case REQ_POST:
 160         sem_post(request.req_args.post);
 161         break;
 162       case REQ_DEBUG:
 163         /* Make gdb aware of new thread */
 164         if (__pthread_threads_debug) raise(PTHREAD_SIG_CANCEL);
 165         restart(request.req_thread);
 166         break;
 167       }
 168     }
 169   }
 170 }
 171
 172 /* Process creation */
 173
 174 static int pthread_start_thread(void *arg)
 175 {
 176   pthread_descr self = (pthread_descr) arg;
 177   struct pthread_request request;
 178   void * outcome;
 179   /* Initialize special thread_self processing, if any.  */
 180 #ifdef INIT_THREAD_SELF
 181   INIT_THREAD_SELF(self);
 182 #endif
 183   /* Make sure our pid field is initialized, just in case we get there
 184      before our father has initialized it. */
 185   self->p_pid = __getpid();
 186   /* Initial signal mask is that of the creating thread. (Otherwise,
 187      we'd just inherit the mask of the thread manager.) */
 188   sigprocmask(SIG_SETMASK, &self->p_start_args.mask, NULL);
 189   /* Set the scheduling policy and priority for the new thread, if needed */
 190   if (self->p_start_args.schedpolicy >= 0)
 191     __sched_setscheduler(self->p_pid, self->p_start_args.schedpolicy,
 192                          &self->p_start_args.schedparam);
 193   /* Make gdb aware of new thread */
 194   if (__pthread_threads_debug) {
 195     request.req_thread = self;
 196     request.req_kind = REQ_DEBUG;
 197     __libc_write(__pthread_manager_request,
 198                  (char *) &request, sizeof(request));
 199     suspend(self);
 200   }
 201   /* Run the thread code */
 202   outcome = self->p_start_args.start_routine(self->p_start_args.arg);
 203   /* Exit with the given return value */
 204   pthread_exit(outcome);
 205   return 0;
 206 }
 207
 208 static int pthread_handle_create(pthread_t *thread, const pthread_attr_t *attr,
 209                                  void * (*start_routine)(void *), void *arg,
 210                                  sigset_t * mask, int father_pid)
 211 {
 212   size_t sseg;
 213   int pid;
 214   pthread_descr new_thread;
 215   char * new_thread_bottom;
 216   pthread_t new_thread_id;
 217   void *guardaddr = NULL;
 218   size_t guardsize = 0;
 219
 220   /* Find a free stack segment for the current stack */
 221   for (sseg = 1; ; sseg++)
 222     {
 223       if (sseg >= PTHREAD_THREADS_MAX)
 224         return EAGAIN;
 225       if (__pthread_handles[sseg].h_descr != NULL)
 226         continue;
 227
 228       if (attr == NULL || !attr->stackaddr_set)
 229         {
 230           new_thread = thread_segment(sseg);
 231           new_thread_bottom = (char *) new_thread - STACK_SIZE;
 232           /* Allocate space for stack and thread descriptor. */
 233           if (mmap((caddr_t)((char *)(new_thread+1) - INITIAL_STACK_SIZE),
 234                    INITIAL_STACK_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
 235                    MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED | MAP_GROWSDOWN,
 236                    -1, 0) != MAP_FAILED)
 237             {
 238               /* We manage to get a stack.  Now see whether we need a guard
 239                  and allocate it if necessary.  */
 240               if (attr == NULL || attr->guardsize != 0)
 241                 {
 242                   guardsize = attr ? attr->guardsize : __getpagesize ();
 243                   guardaddr = mmap ((caddr_t)((char *)(new_thread+1)
 244                                               - STACK_SIZE),
 245                                     guardsize, 0, MAP_FIXED, -1, 0);
 246                   if (guardaddr == MAP_FAILED)
 247                     {
 248                       /* We don't make this an error.  */
 249                       guardaddr = NULL;
 250                       guardsize = 0;
 251                     }
 252                 }
 253               break;
 254             }
 255           /* It seems part of this segment is already mapped. Try the next. */
 256         }
 257       else
 258         {
 259           new_thread = (pthread_descr) ((long) attr->stackaddr
 260                                         & -sizeof(void *)) - 1;
 261           new_thread_bottom = (char *) attr->stackaddr - attr->stacksize;
 262           break;
 263         }
 264     }
 265   /* Allocate new thread identifier */
 266   pthread_threads_counter += PTHREAD_THREADS_MAX;
 267   new_thread_id = sseg + pthread_threads_counter;
 268   /* Initialize the thread descriptor */
 269   new_thread->p_nextwaiting = NULL;
 270   new_thread->p_tid = new_thread_id;
 271   new_thread->p_priority = 0;
 272   new_thread->p_lock = &(__pthread_handles[sseg].h_lock);
 273   new_thread->p_signal = 0;
 274   new_thread->p_signal_jmp = NULL;
 275   new_thread->p_cancel_jmp = NULL;
 276   new_thread->p_terminated = 0;
 277   new_thread->p_detached = attr == NULL ? 0 : attr->detachstate;
 278   new_thread->p_exited = 0;
 279   new_thread->p_retval = NULL;
 280   new_thread->p_joining = NULL;
 281   new_thread->p_cleanup = NULL;
 282   new_thread->p_cancelstate = PTHREAD_CANCEL_ENABLE;
 283   new_thread->p_canceltype = PTHREAD_CANCEL_DEFERRED;
 284   new_thread->p_canceled = 0;
 285   new_thread->p_errnop = &new_thread->p_errno;
 286   new_thread->p_errno = 0;
 287   new_thread->p_h_errnop = &new_thread->p_h_errno;
 288   new_thread->p_h_errno = 0;
 289   new_thread->p_in_sighandler = NULL;
 290   new_thread->p_sigwaiting = 0;
 291   new_thread->p_guardaddr = guardaddr;
 292   new_thread->p_guardsize = guardsize;
 293   new_thread->p_userstack = attr != NULL && attr->stackaddr_set;
 294   memset (new_thread->p_specific, '\0',
 295           PTHREAD_KEY_1STLEVEL_SIZE * sizeof (new_thread->p_specific[0]));
 296   /* Initialize the thread handle */
 297   __pthread_init_lock(&__pthread_handles[sseg].h_lock);
 298   __pthread_handles[sseg].h_descr = new_thread;
 299   __pthread_handles[sseg].h_bottom = new_thread_bottom;
 300   /* Determine scheduling parameters for the thread */
 301   new_thread->p_start_args.schedpolicy = -1;
 302   if (attr != NULL) {
 303     switch(attr->inheritsched) {
 304     case PTHREAD_EXPLICIT_SCHED:
 305       new_thread->p_start_args.schedpolicy = attr->schedpolicy;
 306       memcpy (&new_thread->p_start_args.schedparam, &attr->schedparam,
 307               sizeof (struct sched_param));
 308       break;
 309     case PTHREAD_INHERIT_SCHED:
 310       /* schedpolicy doesn't need to be set, only get priority */
 311       __sched_getparam(father_pid, &new_thread->p_start_args.schedparam);
 312       break;
 313     }
 314     new_thread->p_priority =
 315       new_thread->p_start_args.schedparam.sched_priority;
 316   }
 317   /* Finish setting up arguments to pthread_start_thread */
 318   new_thread->p_start_args.start_routine = start_routine;
 319   new_thread->p_start_args.arg = arg;
 320   new_thread->p_start_args.mask = *mask;
 321   /* Raise priority of thread manager if needed */
 322   __pthread_manager_adjust_prio(new_thread->p_priority);
 323   /* Do the cloning */
 324   pid = __clone(pthread_start_thread, (void **) new_thread,
 325                 CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND |
 326                 PTHREAD_SIG_RESTART,
 327                 new_thread);
 328   /* Check if cloning succeeded */
 329   if (pid == -1) {
 330     /* Free the stack if we allocated it */
 331     if (attr == NULL || !attr->stackaddr_set)
 332       {
 333         munmap((caddr_t)((char *)(new_thread+1) - INITIAL_STACK_SIZE),
 334                INITIAL_STACK_SIZE);
 335         if (new_thread->p_guardsize != 0)
 336           munmap(new_thread->p_guardaddr, new_thread->p_guardsize);
 337       }
 338     __pthread_handles[sseg].h_descr = NULL;
 339     __pthread_handles[sseg].h_bottom = NULL;
 340     __pthread_handles_num--;
 341     return errno;
 342   }
 343   /* Insert new thread in doubly linked list of active threads */
 344   new_thread->p_prevlive = __pthread_main_thread;
 345   new_thread->p_nextlive = __pthread_main_thread->p_nextlive;
 346   __pthread_main_thread->p_nextlive->p_prevlive = new_thread;
 347   __pthread_main_thread->p_nextlive = new_thread;
 348   /* Set pid field of the new thread, in case we get there before the
 349      child starts. */
 350   new_thread->p_pid = pid;
 351   /* We're all set */
 352   *thread = new_thread_id;
 353   return 0;
 354 }
 355
 356
 357 /* Try to free the resources of a thread when requested by pthread_join
 358    or pthread_detach on a terminated thread. */
 359
 360 static void pthread_free(pthread_descr th)
 361 {
 362   pthread_handle handle;
 363   ASSERT(th->p_exited);
 364   /* Make the handle invalid */
 365   handle =  thread_handle(th->p_tid);
 366   __pthread_lock(&handle->h_lock);
 367   handle->h_descr = NULL;
 368   handle->h_bottom = (char *)(-1L);
 369   __pthread_unlock(&handle->h_lock);
 370   /* One fewer threads in __pthread_handles */
 371   __pthread_handles_num--;
 372   /* If initial thread, nothing to free */
 373   if (th == &__pthread_initial_thread) return;
 374   if (!th->p_userstack)
 375     {
 376       /* Free the stack and thread descriptor area */
 377       if (th->p_guardsize != 0)
 378         munmap(th->p_guardaddr, th->p_guardsize);
 379       munmap((caddr_t) ((char *)(th+1) - STACK_SIZE), STACK_SIZE);
 380     }
 381 }
 382
 383 /* Handle threads that have exited */
 384
 385 static void pthread_exited(pid_t pid)
 386 {
 387   pthread_descr th;
 388   int detached;
 389   /* Find thread with that pid */
 390   for (th = __pthread_main_thread->p_nextlive;
 391        th != __pthread_main_thread;
 392        th = th->p_nextlive) {
 393     if (th->p_pid == pid) {
 394       /* Remove thread from list of active threads */
 395       th->p_nextlive->p_prevlive = th->p_prevlive;
 396       th->p_prevlive->p_nextlive = th->p_nextlive;
 397       /* Mark thread as exited, and if detached, free its resources */
 398       __pthread_lock(th->p_lock);
 399       th->p_exited = 1;
 400       detached = th->p_detached;
 401       __pthread_unlock(th->p_lock);
 402       if (detached)
 403         pthread_free(th);
 404       break;
 405     }
 406   }
 407   /* If all threads have exited and the main thread is pending on a
 408      pthread_exit, wake up the main thread and terminate ourselves. */
 409   if (main_thread_exiting &&
 410       __pthread_main_thread->p_nextlive == __pthread_main_thread) {
 411     restart(__pthread_main_thread);
 412     _exit(0);
 413   }
 414 }
 415
 416 static void pthread_reap_children(void)
 417 {
 418   pid_t pid;
 419   int status;
 420
 421   while ((pid = __libc_waitpid(-1, &status, WNOHANG | __WCLONE)) > 0) {
 422     pthread_exited(pid);
 423     if (WIFSIGNALED(status)) {
 424       /* If a thread died due to a signal, send the same signal to
 425          all other threads, including the main thread. */
 426       pthread_kill_all_threads(WTERMSIG(status), 1);
 427       _exit(0);
 428     }
 429   }
 430 }
 431
 432 /* Try to free the resources of a thread when requested by pthread_join
 433    or pthread_detach on a terminated thread. */
 434
 435 static void pthread_handle_free(pthread_t th_id)
 436 {
 437   pthread_handle handle = thread_handle(th_id);
 438   pthread_descr th;
 439
 440   __pthread_lock(&handle->h_lock);
 441   if (invalid_handle(handle, th_id)) {
 442     /* pthread_reap_children has deallocated the thread already,
 443        nothing needs to be done */
 444     __pthread_unlock(&handle->h_lock);
 445     return;
 446   }
 447   th = handle->h_descr;
 448   if (th->p_exited) {
 449     __pthread_unlock(&handle->h_lock);
 450     pthread_free(th);
 451   } else {
 452     /* The Unix process of the thread is still running.
 453        Mark the thread as detached so that the thread manager will
 454        deallocate its resources when the Unix process exits. */
 455     th->p_detached = 1;
 456     __pthread_unlock(&handle->h_lock);
 457   }
 458 }
 459
 460 /* Send a signal to all running threads */
 461
 462 static void pthread_kill_all_threads(int sig, int main_thread_also)
 463 {
 464   pthread_descr th;
 465   for (th = __pthread_main_thread->p_nextlive;
 466        th != __pthread_main_thread;
 467        th = th->p_nextlive) {
 468     kill(th->p_pid, sig);
 469   }
 470   if (main_thread_also) {
 471     kill(__pthread_main_thread->p_pid, sig);
 472   }
 473 }
 474
 475 /* Process-wide exit() */
 476
 477 static void pthread_handle_exit(pthread_descr issuing_thread, int exitcode)
 478 {
 479   pthread_descr th;
 480   __pthread_exit_requested = 1;
 481   __pthread_exit_code = exitcode;
 482   /* Send the CANCEL signal to all running threads, including the main
 483      thread, but excluding the thread from which the exit request originated
 484      (that thread must complete the exit, e.g. calling atexit functions
 485      and flushing stdio buffers). */
 486   for (th = issuing_thread->p_nextlive;
 487        th != issuing_thread;
 488        th = th->p_nextlive) {
 489     kill(th->p_pid, PTHREAD_SIG_CANCEL);
 490   }
 491   /* Now, wait for all these threads, so that they don't become zombies
 492      and their times are properly added to the thread manager's times. */
 493   for (th = issuing_thread->p_nextlive;
 494        th != issuing_thread;
 495        th = th->p_nextlive) {
 496     waitpid(th->p_pid, NULL, __WCLONE);
 497   }
 498   restart(issuing_thread);
 499   _exit(0);
 500 }
 501
 502 /* Handler for PTHREAD_SIG_RESTART in thread manager thread */
 503
 504 void __pthread_manager_sighandler(int sig)
 505 {
 506   terminated_children = 1;
 507 }
 508
 509 /* Adjust priority of thread manager so that it always run at a priority
 510    higher than all threads */
 511
 512 void __pthread_manager_adjust_prio(int thread_prio)
 513 {
 514   struct sched_param param;
 515
 516   if (thread_prio <= __pthread_manager_thread.p_priority) return;
 517   param.sched_priority =
 518     thread_prio < __sched_get_priority_max(SCHED_FIFO)
 519     ? thread_prio + 1 : thread_prio;
 520   __sched_setscheduler(__pthread_manager_thread.p_pid, SCHED_FIFO, &param);
 521   __pthread_manager_thread.p_priority = thread_prio;
 522 }