server/thread.c

   1 /*
   2  * Server-side thread management
   3  *
   4  * Copyright (C) 1998 Alexandre Julliard
   5  */
   6
   7 #include "config.h"
   8
   9 #include <assert.h>
  10 #include <fcntl.h>
  11 #include <signal.h>
  12 #include <stdio.h>
  13 #include <stdlib.h>
  14 #include <string.h>
  15 #ifdef HAVE_SYS_MMAN_H
  16 #include <sys/mman.h>
  17 #endif
  18 #include <sys/types.h>
  19 #ifdef HAVE_SYS_SOCKET_H
  20 # include <sys/socket.h>
  21 #endif
  22 #include <sys/uio.h>
  23 #include <unistd.h>
  24 #include <stdarg.h>
  25
  26
  27 #include "winbase.h"
  28
  29 #include "handle.h"
  30 #include "process.h"
  31 #include "thread.h"
  32 #include "request.h"
  33
  34
  35 /* thread queues */
  36
  37 struct wait_queue_entry
  38 {
  39     struct wait_queue_entry *next;
  40     struct wait_queue_entry *prev;
  41     struct object           *obj;
  42     struct thread           *thread;
  43 };
  44
  45 struct thread_wait
  46 {
  47     int                     count;      /* count of objects */
  48     int                     flags;
  49     struct timeval          timeout;
  50     struct timeout_user    *user;
  51     sleep_reply             reply;      /* function to build the reply */
  52     struct wait_queue_entry queues[1];
  53 };
  54
  55 /* asynchronous procedure calls */
  56
  57 struct thread_apc
  58 {
  59     void                   *func;    /* function to call in client */
  60     void                   *param;   /* function param */
  61 };
  62 #define MAX_THREAD_APC  16  /* Max outstanding APCs for a thread */
  63
  64
  65 /* thread operations */
  66
  67 static void dump_thread( struct object *obj, int verbose );
  68 static int thread_signaled( struct object *obj, struct thread *thread );
  69 extern void thread_poll_event( struct object *obj, int event );
  70 static void destroy_thread( struct object *obj );
  71
  72 static const struct object_ops thread_ops =
  73 {
  74     sizeof(struct thread),      /* size */
  75     dump_thread,                /* dump */
  76     add_queue,                  /* add_queue */
  77     remove_queue,               /* remove_queue */
  78     thread_signaled,            /* signaled */
  79     no_satisfied,               /* satisfied */
  80     NULL,                       /* get_poll_events */
  81     thread_poll_event,          /* poll_event */
  82     no_read_fd,                 /* get_read_fd */
  83     no_write_fd,                /* get_write_fd */
  84     no_flush,                   /* flush */
  85     no_get_file_info,           /* get_file_info */
  86     destroy_thread              /* destroy */
  87 };
  88
  89 static struct thread *first_thread;
  90 static struct thread *booting_thread;
  91
  92 /* allocate the buffer for the communication with the client */
  93 static int alloc_client_buffer( struct thread *thread )
  94 {
  95     struct get_thread_buffer_request *req;
  96     int fd;
  97
  98     if ((fd = create_anonymous_file()) == -1) return -1;
  99     if (ftruncate( fd, MAX_REQUEST_LENGTH ) == -1) goto error;
 100     if ((thread->buffer = mmap( 0, MAX_REQUEST_LENGTH, PROT_READ | PROT_WRITE,
 101                                 MAP_SHARED, fd, 0 )) == (void*)-1) goto error;
 102     /* build the first request into the buffer and send it */
 103     req = thread->buffer;
 104     req->pid  = get_process_id( thread->process );
 105     req->tid  = get_thread_id( thread );
 106     req->boot = (thread == booting_thread);
 107     req->version = SERVER_PROTOCOL_VERSION;
 108     set_reply_fd( thread, fd );
 109     send_reply( thread );
 110     return 1;
 111
 112  error:
 113     file_set_error();
 114     if (fd != -1) close( fd );
 115     return 0;
 116 }
 117
 118 /* create a new thread */
 119 struct thread *create_thread( int fd, struct process *process, int suspend )
 120 {
 121     struct thread *thread;
 122
 123     int flags = fcntl( fd, F_GETFL, 0 );
 124     fcntl( fd, F_SETFL, flags | O_NONBLOCK );
 125
 126     if (!(thread = alloc_object( &thread_ops, fd ))) return NULL;
 127
 128     thread->unix_pid    = 0;  /* not known yet */
 129     thread->context     = NULL;
 130     thread->teb         = NULL;
 131     thread->mutex       = NULL;
 132     thread->debug_ctx   = NULL;
 133     thread->wait        = NULL;
 134     thread->apc         = NULL;
 135     thread->apc_count   = 0;
 136     thread->error       = 0;
 137     thread->pass_fd     = -1;
 138     thread->state       = RUNNING;
 139     thread->attached    = 0;
 140     thread->exit_code   = 0;
 141     thread->next        = NULL;
 142     thread->prev        = NULL;
 143     thread->priority    = THREAD_PRIORITY_NORMAL;
 144     thread->affinity    = 1;
 145     thread->suspend     = (suspend != 0);
 146     thread->buffer      = (void *)-1;
 147     thread->last_req    = REQ_GET_THREAD_BUFFER;
 148     thread->process     = (struct process *)grab_object( process );
 149
 150     if (!current) current = thread;
 151
 152     if (!booting_thread)  /* first thread ever */
 153     {
 154         booting_thread = thread;
 155         lock_master_socket(1);
 156     }
 157
 158     if ((thread->next = first_thread) != NULL) thread->next->prev = thread;
 159     first_thread = thread;
 160     add_process_thread( process, thread );
 161
 162     set_select_events( &thread->obj, POLLIN );  /* start listening to events */
 163     if (!alloc_client_buffer( thread )) goto error;
 164     return thread;
 165
 166  error:
 167     remove_process_thread( process, thread );
 168     release_object( thread );
 169     return NULL;
 170 }
 171
 172 /* handle a client event */
 173 void thread_poll_event( struct object *obj, int event )
 174 {
 175     struct thread *thread = (struct thread *)obj;
 176     assert( obj->ops == &thread_ops );
 177
 178     if (event & (POLLERR | POLLHUP)) kill_thread( thread, 0 );
 179     else
 180     {
 181         if (event & POLLOUT) write_request( thread );
 182         if (event & POLLIN) read_request( thread );
 183     }
 184 }
 185
 186 /* destroy a thread when its refcount is 0 */
 187 static void destroy_thread( struct object *obj )
 188 {
 189     struct thread *thread = (struct thread *)obj;
 190     assert( obj->ops == &thread_ops );
 191
 192     assert( !thread->debug_ctx );  /* cannot still be debugging something */
 193     release_object( thread->process );
 194     if (thread->next) thread->next->prev = thread->prev;
 195     if (thread->prev) thread->prev->next = thread->next;
 196     else first_thread = thread->next;
 197     if (thread->apc) free( thread->apc );
 198     if (thread->buffer != (void *)-1) munmap( thread->buffer, MAX_REQUEST_LENGTH );
 199     if (thread->pass_fd != -1) close( thread->pass_fd );
 200 }
 201
 202 /* dump a thread on stdout for debugging purposes */
 203 static void dump_thread( struct object *obj, int verbose )
 204 {
 205     struct thread *thread = (struct thread *)obj;
 206     assert( obj->ops == &thread_ops );
 207
 208     fprintf( stderr, "Thread pid=%d teb=%p state=%d\n",
 209              thread->unix_pid, thread->teb, thread->state );
 210 }
 211
 212 static int thread_signaled( struct object *obj, struct thread *thread )
 213 {
 214     struct thread *mythread = (struct thread *)obj;
 215     return (mythread->state == TERMINATED);
 216 }
 217
 218 /* get a thread pointer from a thread id (and increment the refcount) */
 219 struct thread *get_thread_from_id( void *id )
 220 {
 221     struct thread *t = first_thread;
 222     while (t && (t != id)) t = t->next;
 223     if (t) grab_object( t );
 224     return t;
 225 }
 226
 227 /* get a thread from a handle (and increment the refcount) */
 228 struct thread *get_thread_from_handle( int handle, unsigned int access )
 229 {
 230     return (struct thread *)get_handle_obj( current->process, handle,
 231                                             access, &thread_ops );
 232 }
 233
 234 /* find a thread from a Unix pid */
 235 struct thread *get_thread_from_pid( int pid )
 236 {
 237     struct thread *t = first_thread;
 238     while (t && (t->unix_pid != pid)) t = t->next;
 239     return t;
 240 }
 241
 242 /* set all information about a thread */
 243 static void set_thread_info( struct thread *thread,
 244                              struct set_thread_info_request *req )
 245 {
 246     if (req->mask & SET_THREAD_INFO_PRIORITY)
 247         thread->priority = req->priority;
 248     if (req->mask & SET_THREAD_INFO_AFFINITY)
 249     {
 250         if (req->affinity != 1) set_error( STATUS_INVALID_PARAMETER );
 251         else thread->affinity = req->affinity;
 252     }
 253 }
 254
 255 /* suspend a thread */
 256 int suspend_thread( struct thread *thread, int check_limit )
 257 {
 258     int old_count = thread->suspend;
 259     if (thread->suspend < MAXIMUM_SUSPEND_COUNT || !check_limit)
 260     {
 261         if (!(thread->process->suspend + thread->suspend++)) stop_thread( thread );
 262     }
 263     else set_error( STATUS_SUSPEND_COUNT_EXCEEDED );
 264     return old_count;
 265 }
 266
 267 /* resume a thread */
 268 int resume_thread( struct thread *thread )
 269 {
 270     int old_count = thread->suspend;
 271     if (thread->suspend > 0)
 272     {
 273         if (!(--thread->suspend + thread->process->suspend)) continue_thread( thread );
 274     }
 275     return old_count;
 276 }
 277
 278 /* suspend all threads but the current */
 279 void suspend_all_threads( void )
 280 {
 281     struct thread *thread;
 282     for ( thread = first_thread; thread; thread = thread->next )
 283         if ( thread != current )
 284             suspend_thread( thread, 0 );
 285 }
 286
 287 /* resume all threads but the current */
 288 void resume_all_threads( void )
 289 {
 290     struct thread *thread;
 291     for ( thread = first_thread; thread; thread = thread->next )
 292         if ( thread != current )
 293             resume_thread( thread );
 294 }
 295
 296 /* add a thread to an object wait queue; return 1 if OK, 0 on error */
 297 int add_queue( struct object *obj, struct wait_queue_entry *entry )
 298 {
 299     grab_object( obj );
 300     entry->obj    = obj;
 301     entry->prev   = obj->tail;
 302     entry->next   = NULL;
 303     if (obj->tail) obj->tail->next = entry;
 304     else obj->head = entry;
 305     obj->tail = entry;
 306     return 1;
 307 }
 308
 309 /* remove a thread from an object wait queue */
 310 void remove_queue( struct object *obj, struct wait_queue_entry *entry )
 311 {
 312     if (entry->next) entry->next->prev = entry->prev;
 313     else obj->tail = entry->prev;
 314     if (entry->prev) entry->prev->next = entry->next;
 315     else obj->head = entry->next;
 316     release_object( obj );
 317 }
 318
 319 /* finish waiting */
 320 static void end_wait( struct thread *thread )
 321 {
 322     struct thread_wait *wait = thread->wait;
 323     struct wait_queue_entry *entry;
 324     int i;
 325
 326     assert( wait );
 327     for (i = 0, entry = wait->queues; i < wait->count; i++, entry++)
 328         entry->obj->ops->remove_queue( entry->obj, entry );
 329     if (wait->user) remove_timeout_user( wait->user );
 330     free( wait );
 331     thread->wait = NULL;
 332 }
 333
 334 /* build the thread wait structure */
 335 static int wait_on( int count, struct object *objects[], int flags,
 336                     int timeout, sleep_reply func )
 337 {
 338     struct thread_wait *wait;
 339     struct wait_queue_entry *entry;
 340     int i;
 341
 342     if (!(wait = mem_alloc( sizeof(*wait) + (count-1) * sizeof(*entry) ))) return 0;
 343     current->wait = wait;
 344     wait->count   = count;
 345     wait->flags   = flags;
 346     wait->user    = NULL;
 347     wait->reply   = func;
 348     if (flags & SELECT_TIMEOUT)
 349     {
 350         gettimeofday( &wait->timeout, 0 );
 351         add_timeout( &wait->timeout, timeout );
 352     }
 353
 354     for (i = 0, entry = wait->queues; i < count; i++, entry++)
 355     {
 356         struct object *obj = objects[i];
 357         entry->thread = current;
 358         if (!obj->ops->add_queue( obj, entry ))
 359         {
 360             wait->count = i;
 361             end_wait( current );
 362             return 0;
 363         }
 364     }
 365     return 1;
 366 }
 367
 368 /* check if the thread waiting condition is satisfied */
 369 static int check_wait( struct thread *thread, struct object **object )
 370 {
 371     int i, signaled;
 372     struct thread_wait *wait = thread->wait;
 373     struct wait_queue_entry *entry = wait->queues;
 374
 375     assert( wait );
 376     *object = NULL;
 377     if (wait->flags & SELECT_ALL)
 378     {
 379         int not_ok = 0;
 380         /* Note: we must check them all anyway, as some objects may
 381          * want to do something when signaled, even if others are not */
 382         for (i = 0, entry = wait->queues; i < wait->count; i++, entry++)
 383             not_ok |= !entry->obj->ops->signaled( entry->obj, thread );
 384         if (not_ok) goto other_checks;
 385         /* Wait satisfied: tell it to all objects */
 386         signaled = 0;
 387         for (i = 0, entry = wait->queues; i < wait->count; i++, entry++)
 388             if (entry->obj->ops->satisfied( entry->obj, thread ))
 389                 signaled = STATUS_ABANDONED_WAIT_0;
 390         return signaled;
 391     }
 392     else
 393     {
 394         for (i = 0, entry = wait->queues; i < wait->count; i++, entry++)
 395         {
 396             if (!entry->obj->ops->signaled( entry->obj, thread )) continue;
 397             /* Wait satisfied: tell it to the object */
 398             signaled = i;
 399             *object = entry->obj;
 400             if (entry->obj->ops->satisfied( entry->obj, thread ))
 401                 signaled = i + STATUS_ABANDONED_WAIT_0;
 402             return signaled;
 403         }
 404     }
 405
 406  other_checks:
 407     if ((wait->flags & SELECT_ALERTABLE) && thread->apc) return STATUS_USER_APC;
 408     if (wait->flags & SELECT_TIMEOUT)
 409     {
 410         struct timeval now;
 411         gettimeofday( &now, NULL );
 412         if (!time_before( &now, &wait->timeout )) return STATUS_TIMEOUT;
 413     }
 414     return -1;
 415 }
 416
 417 /* build a reply to the select request */
 418 static void build_select_reply( struct thread *thread, struct object *obj, int signaled )
 419 {
 420     struct select_request *req = get_req_ptr( thread );
 421     req->signaled = signaled;
 422 }
 423
 424 /* attempt to wake up a thread */
 425 /* return 1 if OK, 0 if the wait condition is still not satisfied */
 426 static int wake_thread( struct thread *thread )
 427 {
 428     int signaled;
 429     struct object *object;
 430     if ((signaled = check_wait( thread, &object )) == -1) return 0;
 431     thread->error = 0;
 432     thread->wait->reply( thread, object, signaled );
 433     end_wait( thread );
 434     return 1;
 435 }
 436
 437 /* thread wait timeout */
 438 static void thread_timeout( void *ptr )
 439 {
 440     struct thread *thread = ptr;
 441     if (debug_level) fprintf( stderr, "%08x: *timeout*\n", (unsigned int)thread );
 442     assert( thread->wait );
 443     thread->error = 0;
 444     thread->wait->user = NULL;
 445     thread->wait->reply( thread, NULL, STATUS_TIMEOUT );
 446     end_wait( thread );
 447     send_reply( thread );
 448 }
 449
 450 /* sleep on a list of objects */
 451 int sleep_on( int count, struct object *objects[], int flags, int timeout, sleep_reply func )
 452 {
 453     assert( !current->wait );
 454     if (!wait_on( count, objects, flags, timeout, func )) return 0;
 455     if (wake_thread( current )) return 1;
 456     /* now we need to wait */
 457     if (flags & SELECT_TIMEOUT)
 458     {
 459         if (!(current->wait->user = add_timeout_user( &current->wait->timeout,
 460                                                       thread_timeout, current )))
 461         {
 462             end_wait( current );
 463             return 0;
 464         }
 465     }
 466     return 1;
 467 }
 468
 469 /* select on a list of handles */
 470 static int select_on( int count, int *handles, int flags, int timeout )
 471 {
 472     int ret = 0;
 473     int i;
 474     struct object *objects[MAXIMUM_WAIT_OBJECTS];
 475
 476     if ((count < 0) || (count > MAXIMUM_WAIT_OBJECTS))
 477     {
 478         set_error( STATUS_INVALID_PARAMETER );
 479         return 0;
 480     }
 481     for (i = 0; i < count; i++)
 482     {
 483         if (!(objects[i] = get_handle_obj( current->process, handles[i], SYNCHRONIZE, NULL )))
 484             break;
 485     }
 486     if (i == count) ret = sleep_on( count, objects, flags, timeout, build_select_reply );
 487     while (--i >= 0) release_object( objects[i] );
 488     return ret;
 489 }
 490
 491 /* attempt to wake threads sleeping on the object wait queue */
 492 void wake_up( struct object *obj, int max )
 493 {
 494     struct wait_queue_entry *entry = obj->head;
 495
 496     while (entry)
 497     {
 498         struct thread *thread = entry->thread;
 499         entry = entry->next;
 500         if (wake_thread( thread ))
 501         {
 502             send_reply( thread );
 503             if (max && !--max) break;
 504         }
 505     }
 506 }
 507
 508 /* queue an async procedure call */
 509 static int thread_queue_apc( struct thread *thread, void *func, void *param )
 510 {
 511     struct thread_apc *apc;
 512     if (!thread->apc)
 513     {
 514         if (!(thread->apc = mem_alloc( MAX_THREAD_APC * sizeof(*apc) )))
 515             return 0;
 516         thread->apc_count = 0;
 517     }
 518     else if (thread->apc_count >= MAX_THREAD_APC) return 0;
 519     thread->apc[thread->apc_count].func  = func;
 520     thread->apc[thread->apc_count].param = param;
 521     thread->apc_count++;
 522     if (thread->wait)
 523     {
 524         if (wake_thread( thread )) send_reply( thread );
 525     }
 526     return 1;
 527 }
 528
 529 /* retrieve an LDT selector entry */
 530 static void get_selector_entry( struct thread *thread, int entry,
 531                                 unsigned int *base, unsigned int *limit,
 532                                 unsigned char *flags )
 533 {
 534     if (!thread->process->ldt_copy || !thread->process->ldt_flags)
 535     {
 536         set_error( STATUS_ACCESS_DENIED );
 537         return;
 538     }
 539     if (entry >= 8192)
 540     {
 541         set_error( STATUS_INVALID_PARAMETER );  /* FIXME */
 542         return;
 543     }
 544     if (suspend_for_ptrace( thread ))
 545     {
 546         unsigned char flags_buf[4];
 547         int *addr = (int *)thread->process->ldt_copy + 2 * entry;
 548         if (read_thread_int( thread, addr, base ) == -1) goto done;
 549         if (read_thread_int( thread, addr + 1, limit ) == -1) goto done;
 550         addr = (int *)thread->process->ldt_flags + (entry >> 2);
 551         if (read_thread_int( thread, addr, (int *)flags_buf ) == -1) goto done;
 552         *flags = flags_buf[entry & 3];
 553     done:
 554         resume_thread( thread );
 555     }
 556 }
 557
 558 /* kill a thread on the spot */
 559 void kill_thread( struct thread *thread, int violent_death )
 560 {
 561     if (thread->state == TERMINATED) return;  /* already killed */
 562     thread->state = TERMINATED;
 563     if (current == thread) current = NULL;
 564     if (debug_level)
 565         fprintf( stderr,"%08x: *killed* exit_code=%d\n",
 566                  (unsigned int)thread, thread->exit_code );
 567     if (thread->wait)
 568     {
 569         end_wait( thread );
 570         /* if it is waiting on the socket, we don't need to send a SIGTERM */
 571         violent_death = 0;
 572     }
 573     debug_exit_thread( thread );
 574     abandon_mutexes( thread );
 575     remove_process_thread( thread->process, thread );
 576     wake_up( &thread->obj, 0 );
 577     detach_thread( thread, violent_death ? SIGTERM : 0 );
 578     remove_select_user( &thread->obj );
 579     release_object( thread );
 580 }
 581
 582 /* signal that we are finished booting on the client side */
 583 DECL_HANDLER(boot_done)
 584 {
 585     debug_level = req->debug_level;
 586     /* Make sure last_req is initialized */
 587     current->last_req = REQ_BOOT_DONE;
 588     if (current == booting_thread)
 589     {
 590         booting_thread = (struct thread *)~0UL;  /* make sure it doesn't match other threads */
 591         lock_master_socket(0);  /* allow other clients now */
 592     }
 593 }
 594
 595 /* create a new thread */
 596 DECL_HANDLER(new_thread)
 597 {
 598     struct thread *thread;
 599     int sock[2];
 600
 601     if (socketpair( AF_UNIX, SOCK_STREAM, 0, sock ) != -1)
 602     {
 603         if ((thread = create_thread( sock[0], current->process, req->suspend )))
 604         {
 605             req->tid = thread;
 606             if ((req->handle = alloc_handle( current->process, thread,
 607                                              THREAD_ALL_ACCESS, req->inherit )) != -1)
 608             {
 609                 set_reply_fd( current, sock[1] );
 610                 /* thread object will be released when the thread gets killed */
 611                 return;
 612             }
 613             release_object( thread );
 614         }
 615         close( sock[1] );
 616     }
 617     else file_set_error();
 618 }
 619
 620 /* retrieve the thread buffer file descriptor */
 621 DECL_HANDLER(get_thread_buffer)
 622 {
 623     fatal_protocol_error( current, "get_thread_buffer: should never get called directly\n" );
 624 }
 625
 626 /* initialize a new thread */
 627 DECL_HANDLER(init_thread)
 628 {
 629     if (current->unix_pid)
 630     {
 631         fatal_protocol_error( current, "init_thread: already running\n" );
 632         return;
 633     }
 634     current->unix_pid = req->unix_pid;
 635     current->teb      = req->teb;
 636     current->entry    = req->entry;
 637     if (current->suspend + current->process->suspend > 0) stop_thread( current );
 638     if (current->process->running_threads > 1)
 639         generate_debug_event( current, CREATE_THREAD_DEBUG_EVENT, current );
 640 }
 641
 642 /* terminate a thread */
 643 DECL_HANDLER(terminate_thread)
 644 {
 645     struct thread *thread;
 646
 647     req->self = 0;
 648     req->last = 0;
 649     if ((thread = get_thread_from_handle( req->handle, THREAD_TERMINATE )))
 650     {
 651         thread->exit_code = req->exit_code;
 652         if (thread != current) kill_thread( thread, 1 );
 653         else
 654         {
 655             req->self = 1;
 656             req->last = (thread->process->running_threads == 1);
 657         }
 658         release_object( thread );
 659     }
 660 }
 661
 662 /* fetch information about a thread */
 663 DECL_HANDLER(get_thread_info)
 664 {
 665     struct thread *thread;
 666
 667     if ((thread = get_thread_from_handle( req->handle, THREAD_QUERY_INFORMATION )))
 668     {
 669         req->tid       = thread;
 670         req->exit_code = (thread->state == TERMINATED) ? thread->exit_code : STILL_ACTIVE;
 671         req->priority  = thread->priority;
 672         release_object( thread );
 673     }
 674 }
 675
 676 /* set information about a thread */
 677 DECL_HANDLER(set_thread_info)
 678 {
 679     struct thread *thread;
 680
 681     if ((thread = get_thread_from_handle( req->handle, THREAD_SET_INFORMATION )))
 682     {
 683         set_thread_info( thread, req );
 684         release_object( thread );
 685     }
 686 }
 687
 688 /* suspend a thread */
 689 DECL_HANDLER(suspend_thread)
 690 {
 691     struct thread *thread;
 692
 693     if ((thread = get_thread_from_handle( req->handle, THREAD_SUSPEND_RESUME )))
 694     {
 695         req->count = suspend_thread( thread, 1 );
 696         release_object( thread );
 697     }
 698 }
 699
 700 /* resume a thread */
 701 DECL_HANDLER(resume_thread)
 702 {
 703     struct thread *thread;
 704
 705     if ((thread = get_thread_from_handle( req->handle, THREAD_SUSPEND_RESUME )))
 706     {
 707         req->count = resume_thread( thread );
 708         release_object( thread );
 709     }
 710 }
 711
 712 /* select on a handle list */
 713 DECL_HANDLER(select)
 714 {
 715     if (!select_on( req->count, req->handles, req->flags, req->timeout ))
 716         req->signaled = -1;
 717 }
 718
 719 /* queue an APC for a thread */
 720 DECL_HANDLER(queue_apc)
 721 {
 722     struct thread *thread;
 723     if ((thread = get_thread_from_handle( req->handle, THREAD_SET_CONTEXT )))
 724     {
 725         thread_queue_apc( thread, req->func, req->param );
 726         release_object( thread );
 727     }
 728 }
 729
 730 /* get list of APC to call */
 731 DECL_HANDLER(get_apcs)
 732 {
 733     if ((req->count = current->apc_count))
 734     {
 735         memcpy( req->apcs, current->apc, current->apc_count * sizeof(*current->apc) );
 736         free( current->apc );
 737         current->apc = NULL;
 738         current->apc_count = 0;
 739     }
 740 }
 741
 742 /* fetch a selector entry for a thread */
 743 DECL_HANDLER(get_selector_entry)
 744 {
 745     struct thread *thread;
 746     if ((thread = get_thread_from_handle( req->handle, THREAD_QUERY_INFORMATION )))
 747     {
 748         get_selector_entry( thread, req->entry, &req->base, &req->limit, &req->flags );
 749         release_object( thread );
 750     }
 751 }