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