server/async.c

   1 /*
   2  * Server-side async I/O support
   3  *
   4  * Copyright (C) 2007 Alexandre Julliard
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  19  */
  20
  21 #include <assert.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <stdarg.h>
  25
  26 #include "ntstatus.h"
  27 #define WIN32_NO_STATUS
  28 #include "windef.h"
  29 #include "winternl.h"
  30
  31 #include "object.h"
  32 #include "file.h"
  33 #include "request.h"
  34 #include "process.h"
  35 #include "handle.h"
  36
  37 struct async
  38 {
  39     struct object        obj;             /* object header */
  40     struct thread       *thread;          /* owning thread */
  41     struct list          queue_entry;     /* entry in async queue list */
  42     struct list          process_entry;   /* entry in process list */
  43     struct async_queue  *queue;           /* queue containing this async */
  44     struct fd           *fd;              /* fd associated with an unqueued async */
  45     struct timeout_user *timeout;
  46     unsigned int         timeout_status;  /* status to report upon timeout */
  47     struct event        *event;
  48     async_data_t         data;            /* data for async I/O call */
  49     struct iosb         *iosb;            /* I/O status block */
  50     obj_handle_t         wait_handle;     /* pre-allocated wait handle */
  51     unsigned int         initial_status;  /* status returned from initial request */
  52     unsigned int         signaled :1;
  53     unsigned int         pending :1;      /* request successfully queued, but pending */
  54     unsigned int         direct_result :1;/* a flag if we're passing result directly from request instead of APC  */
  55     unsigned int         alerted :1;      /* fd is signaled, but we are waiting for client-side I/O */
  56     unsigned int         terminated :1;   /* async has been terminated */
  57     unsigned int         canceled :1;     /* have we already queued cancellation for this async? */
  58     unsigned int         unknown_status :1; /* initial status is not known yet */
  59     unsigned int         blocking :1;     /* async is blocking */
  60     struct completion   *completion;      /* completion associated with fd */
  61     apc_param_t          comp_key;        /* completion key associated with fd */
  62     unsigned int         comp_flags;      /* completion flags */
  63     async_completion_callback completion_callback; /* callback to be called on completion */
  64     void                *completion_callback_private; /* argument to completion_callback */
  65 };
  66
  67 static void async_dump( struct object *obj, int verbose );
  68 static int async_signaled( struct object *obj, struct wait_queue_entry *entry );
  69 static void async_satisfied( struct object * obj, struct wait_queue_entry *entry );
  70 static void async_destroy( struct object *obj );
  71
  72 static const struct object_ops async_ops =
  73 {
  74     sizeof(struct async),      /* size */
  75     &no_type,                  /* type */
  76     async_dump,                /* dump */
  77     add_queue,                 /* add_queue */
  78     remove_queue,              /* remove_queue */
  79     async_signaled,            /* signaled */
  80     async_satisfied,           /* satisfied */
  81     no_signal,                 /* signal */
  82     no_get_fd,                 /* get_fd */
  83     default_map_access,        /* map_access */
  84     default_get_sd,            /* get_sd */
  85     default_set_sd,            /* set_sd */
  86     no_get_full_name,          /* get_full_name */
  87     no_lookup_name,            /* lookup_name */
  88     no_link_name,              /* link_name */
  89     NULL,                      /* unlink_name */
  90     no_open_file,              /* open_file */
  91     no_kernel_obj_list,        /* get_kernel_obj_list */
  92     no_close_handle,           /* close_handle */
  93     async_destroy              /* destroy */
  94 };
  95
  96 static inline void async_reselect( struct async *async )
  97 {
  98     if (async->queue && async->fd) fd_reselect_async( async->fd, async->queue );
  99 }
 100
 101 static void async_dump( struct object *obj, int verbose )
 102 {
 103     struct async *async = (struct async *)obj;
 104     assert( obj->ops == &async_ops );
 105     fprintf( stderr, "Async thread=%p\n", async->thread );
 106 }
 107
 108 static int async_signaled( struct object *obj, struct wait_queue_entry *entry )
 109 {
 110     struct async *async = (struct async *)obj;
 111     assert( obj->ops == &async_ops );
 112     return async->signaled;
 113 }
 114
 115 static void async_satisfied( struct object *obj, struct wait_queue_entry *entry )
 116 {
 117     struct async *async = (struct async *)obj;
 118     assert( obj->ops == &async_ops );
 119
 120     /* we only return an async handle for asyncs created via create_request_async() */
 121     assert( async->iosb );
 122
 123     if (async->direct_result)
 124     {
 125         async_set_result( &async->obj, async->iosb->status, async->iosb->result );
 126         async->direct_result = 0;
 127     }
 128
 129     if (async->initial_status == STATUS_PENDING && async->blocking)
 130         set_wait_status( entry, async->iosb->status );
 131     else
 132         set_wait_status( entry, async->initial_status );
 133
 134     /* close wait handle here to avoid extra server round trip */
 135     if (async->wait_handle)
 136     {
 137         close_handle( async->thread->process, async->wait_handle );
 138         async->wait_handle = 0;
 139     }
 140 }
 141
 142 static void async_destroy( struct object *obj )
 143 {
 144     struct async *async = (struct async *)obj;
 145     assert( obj->ops == &async_ops );
 146
 147     list_remove( &async->process_entry );
 148
 149     if (async->queue)
 150     {
 151         list_remove( &async->queue_entry );
 152         async_reselect( async );
 153     }
 154     else if (async->fd) release_object( async->fd );
 155
 156     if (async->timeout) remove_timeout_user( async->timeout );
 157     if (async->completion) release_object( async->completion );
 158     if (async->event) release_object( async->event );
 159     if (async->iosb) release_object( async->iosb );
 160     release_object( async->thread );
 161 }
 162
 163 /* notifies client thread of new status of its async request */
 164 void async_terminate( struct async *async, unsigned int status )
 165 {
 166     struct iosb *iosb = async->iosb;
 167
 168     if (async->terminated) return;
 169
 170     async->terminated = 1;
 171     if (async->iosb && async->iosb->status == STATUS_PENDING) async->iosb->status = status;
 172     if (status == STATUS_ALERTED)
 173         async->alerted = 1;
 174
 175     /* if no APC could be queued (e.g. the process is terminated),
 176      * thread_queue_apc() may trigger async_set_result(), which may drop the
 177      * last reference to the async, so grab a temporary reference here */
 178     grab_object( async );
 179
 180     if (!async->direct_result)
 181     {
 182         apc_call_t data;
 183
 184         memset( &data, 0, sizeof(data) );
 185         data.type            = APC_ASYNC_IO;
 186         data.async_io.user   = async->data.user;
 187         data.async_io.result = iosb ? iosb->result : 0;
 188
 189         /* this can happen if the initial status was unknown (i.e. for device
 190          * files). the client should not fill the IOSB in this case; pass it as
 191          * NULL to communicate that.
 192          * note that we check the IOSB status and not the initial status */
 193         if (NT_ERROR( status ) && (!is_fd_overlapped( async->fd ) || !async->pending))
 194             data.async_io.sb = 0;
 195         else
 196             data.async_io.sb = async->data.iosb;
 197
 198         /* if there is output data, the client needs to make an extra request
 199          * to retrieve it; use STATUS_ALERTED to signal this case */
 200         if (iosb && iosb->out_data)
 201             data.async_io.status = STATUS_ALERTED;
 202         else
 203             data.async_io.status = status;
 204
 205         thread_queue_apc( async->thread->process, async->thread, &async->obj, &data );
 206     }
 207
 208     async_reselect( async );
 209
 210     release_object( async );
 211 }
 212
 213 /* callback for timeout on an async request */
 214 static void async_timeout( void *private )
 215 {
 216     struct async *async = private;
 217
 218     async->timeout = NULL;
 219     async_terminate( async, async->timeout_status );
 220 }
 221
 222 /* free an async queue, cancelling all async operations */
 223 void free_async_queue( struct async_queue *queue )
 224 {
 225     struct async *async, *next;
 226
 227     LIST_FOR_EACH_ENTRY_SAFE( async, next, &queue->queue, struct async, queue_entry )
 228     {
 229         if (!async->completion) async->completion = fd_get_completion( async->fd, &async->comp_key );
 230         async->fd = NULL;
 231         async_terminate( async, STATUS_HANDLES_CLOSED );
 232         async->queue = NULL;
 233         release_object( &async->obj );
 234     }
 235 }
 236
 237 void queue_async( struct async_queue *queue, struct async *async )
 238 {
 239     /* fd will be set to NULL in free_async_queue when fd is destroyed */
 240     release_object( async->fd );
 241
 242     async->queue = queue;
 243     grab_object( async );
 244     list_add_tail( &queue->queue, &async->queue_entry );
 245
 246     set_fd_signaled( async->fd, 0 );
 247 }
 248
 249 /* create an async on a given queue of a fd */
 250 struct async *create_async( struct fd *fd, struct thread *thread, const async_data_t *data, struct iosb *iosb )
 251 {
 252     struct event *event = NULL;
 253     struct async *async;
 254
 255     if (data->event && !(event = get_event_obj( thread->process, data->event, EVENT_MODIFY_STATE )))
 256         return NULL;
 257
 258     if (!(async = alloc_object( &async_ops )))
 259     {
 260         if (event) release_object( event );
 261         return NULL;
 262     }
 263
 264     async->thread        = (struct thread *)grab_object( thread );
 265     async->event         = event;
 266     async->data          = *data;
 267     async->timeout       = NULL;
 268     async->queue         = NULL;
 269     async->fd            = (struct fd *)grab_object( fd );
 270     async->initial_status = STATUS_PENDING;
 271     async->signaled      = 0;
 272     async->pending       = 1;
 273     async->wait_handle   = 0;
 274     async->direct_result = 0;
 275     async->alerted       = 0;
 276     async->terminated    = 0;
 277     async->canceled      = 0;
 278     async->unknown_status = 0;
 279     async->blocking      = !is_fd_overlapped( fd );
 280     async->completion    = fd_get_completion( fd, &async->comp_key );
 281     async->comp_flags    = 0;
 282     async->completion_callback = NULL;
 283     async->completion_callback_private = NULL;
 284
 285     if (iosb) async->iosb = (struct iosb *)grab_object( iosb );
 286     else async->iosb = NULL;
 287
 288     list_add_head( &thread->process->asyncs, &async->process_entry );
 289     if (event) reset_event( event );
 290
 291     if (async->completion && data->apc)
 292     {
 293         release_object( async );
 294         set_error( STATUS_INVALID_PARAMETER );
 295         return NULL;
 296     }
 297
 298     return async;
 299 }
 300
 301 /* set the initial status of an async whose status was previously unknown
 302  * the initial status may be STATUS_PENDING */
 303 void async_set_initial_status( struct async *async, unsigned int status )
 304 {
 305     async->initial_status = status;
 306     async->unknown_status = 0;
 307 }
 308
 309 void set_async_pending( struct async *async )
 310 {
 311     if (!async->terminated)
 312         async->pending = 1;
 313 }
 314
 315 void async_wake_obj( struct async *async )
 316 {
 317     assert( !async->unknown_status );
 318     if (!async->blocking)
 319     {
 320         async->signaled = 1;
 321         wake_up( &async->obj, 0 );
 322     }
 323 }
 324
 325 static void async_call_completion_callback( struct async *async )
 326 {
 327     if (async->completion_callback)
 328         async->completion_callback( async->completion_callback_private );
 329     async->completion_callback = NULL;
 330 }
 331
 332 /* return async object status and wait handle to client */
 333 obj_handle_t async_handoff( struct async *async, data_size_t *result, int force_blocking )
 334 {
 335     async->blocking = force_blocking || async->blocking;
 336
 337     if (async->unknown_status)
 338     {
 339         /* even the initial status is not known yet */
 340         set_error( STATUS_PENDING );
 341         return async->wait_handle;
 342     }
 343
 344     if (get_error() == STATUS_ALERTED)
 345     {
 346         /* give the client opportunity to complete synchronously.  after the
 347          * client performs the I/O, it reports the result back to the server
 348          * via the set_async_direct_result request.  if it turns out that the
 349          * I/O request is not actually immediately satiable, the client may
 350          * then choose to re-queue the async by reporting STATUS_PENDING
 351          * instead.
 352          *
 353          * since we're deferring the initial I/O (to the client), we mark the
 354          * async as having unknown initial status (unknown_status = 1).  note
 355          * that we don't reuse async_set_unknown_status() here.  this is because
 356          * the one responsible for performing the I/O is not the device driver,
 357          * but instead the client that requested the I/O in the first place.
 358          *
 359          * also, async_set_unknown_status() would set direct_result to zero
 360          * forcing APC_ASYNC_IO to fire in async_terminate(), which is not
 361          * useful due to subtle semantic differences between synchronous and
 362          * asynchronous completion.
 363          */
 364         async->unknown_status = 1;
 365         async_terminate( async, STATUS_ALERTED );
 366         return async->wait_handle;
 367     }
 368
 369     async->initial_status = get_error();
 370
 371     if (!async->pending && NT_ERROR( get_error() ))
 372     {
 373         async->iosb->status = get_error();
 374         async_call_completion_callback( async );
 375
 376         close_handle( async->thread->process, async->wait_handle );
 377         async->wait_handle = 0;
 378         return 0;
 379     }
 380
 381     if (get_error() != STATUS_PENDING)
 382     {
 383         /* status and data are already set and returned */
 384         async_terminate( async, get_error() );
 385     }
 386     else if (async->iosb->status != STATUS_PENDING)
 387     {
 388         /* result is already available in iosb, return it */
 389         if (async->iosb->out_data)
 390         {
 391             set_reply_data_ptr( async->iosb->out_data, async->iosb->out_size );
 392             async->iosb->out_data = NULL;
 393         }
 394     }
 395
 396     if (async->iosb->status != STATUS_PENDING)
 397     {
 398         if (result) *result = async->iosb->result;
 399         async->signaled = 1;
 400     }
 401     else
 402     {
 403         async->direct_result = 0;
 404         async->pending = 1;
 405         if (!async->blocking)
 406         {
 407             close_handle( async->thread->process, async->wait_handle);
 408             async->wait_handle = 0;
 409         }
 410     }
 411     async->initial_status = async->iosb->status;
 412     set_error( async->iosb->status );
 413     return async->wait_handle;
 414 }
 415
 416 /* complete a request-based async with a pre-allocated buffer */
 417 void async_request_complete( struct async *async, unsigned int status, data_size_t result,
 418                              data_size_t out_size, void *out_data )
 419 {
 420     struct iosb *iosb = async_get_iosb( async );
 421
 422     /* the async may have already been canceled */
 423     if (iosb->status != STATUS_PENDING)
 424     {
 425         release_object( iosb );
 426         free( out_data );
 427         return;
 428     }
 429
 430     iosb->status = status;
 431     iosb->result = result;
 432     iosb->out_data = out_data;
 433     iosb->out_size = out_size;
 434
 435     release_object( iosb );
 436
 437     async_terminate( async, status );
 438 }
 439
 440 /* complete a request-based async */
 441 void async_request_complete_alloc( struct async *async, unsigned int status, data_size_t result,
 442                                    data_size_t out_size, const void *out_data )
 443 {
 444     void *out_data_copy = NULL;
 445
 446     if (out_size && !(out_data_copy = memdup( out_data, out_size )))
 447     {
 448         async_terminate( async, STATUS_NO_MEMORY );
 449         return;
 450     }
 451
 452     async_request_complete( async, status, result, out_size, out_data_copy );
 453 }
 454
 455 /* mark an async as having unknown initial status */
 456 void async_set_unknown_status( struct async *async )
 457 {
 458     async->unknown_status = 1;
 459     async->direct_result = 0;
 460 }
 461
 462 /* set the timeout of an async operation */
 463 void async_set_timeout( struct async *async, timeout_t timeout, unsigned int status )
 464 {
 465     if (async->timeout) remove_timeout_user( async->timeout );
 466     if (timeout != TIMEOUT_INFINITE) async->timeout = add_timeout_user( timeout, async_timeout, async );
 467     else async->timeout = NULL;
 468     async->timeout_status = status;
 469 }
 470
 471 /* set a callback to be notified when the async is completed */
 472 void async_set_completion_callback( struct async *async, async_completion_callback func, void *private )
 473 {
 474     async->completion_callback = func;
 475     async->completion_callback_private = private;
 476 }
 477
 478 static void add_async_completion( struct async *async, apc_param_t cvalue, unsigned int status,
 479                                   apc_param_t information )
 480 {
 481     if (async->fd && !async->completion) async->completion = fd_get_completion( async->fd, &async->comp_key );
 482     if (async->completion) add_completion( async->completion, async->comp_key, cvalue, status, information );
 483 }
 484
 485 /* store the result of the client-side async callback */
 486 void async_set_result( struct object *obj, unsigned int status, apc_param_t total )
 487 {
 488     struct async *async = (struct async *)obj;
 489
 490     if (obj->ops != &async_ops) return;  /* in case the client messed up the APC results */
 491
 492     assert( async->terminated );  /* it must have been woken up if we get a result */
 493
 494     if (async->unknown_status) async_set_initial_status( async, status );
 495
 496     if (async->alerted && status == STATUS_PENDING)  /* restart it */
 497     {
 498         async->terminated = 0;
 499         async->alerted = 0;
 500         async_reselect( async );
 501     }
 502     else
 503     {
 504         if (async->timeout) remove_timeout_user( async->timeout );
 505         async->timeout = NULL;
 506         async->terminated = 1;
 507         if (async->iosb) async->iosb->status = status;
 508
 509         /* don't signal completion if the async failed synchronously
 510          * this can happen if the initial status was unknown (i.e. for device files)
 511          * note that we check the IOSB status here, not the initial status */
 512         if (async->pending || !NT_ERROR( status ))
 513         {
 514             if (async->data.apc)
 515             {
 516                 apc_call_t data;
 517                 memset( &data, 0, sizeof(data) );
 518                 data.type         = APC_USER;
 519                 data.user.func    = async->data.apc;
 520                 data.user.args[0] = async->data.apc_context;
 521                 data.user.args[1] = async->data.iosb;
 522                 data.user.args[2] = 0;
 523                 thread_queue_apc( NULL, async->thread, NULL, &data );
 524             }
 525             else if (async->data.apc_context && (async->pending ||
 526                      !(async->comp_flags & FILE_SKIP_COMPLETION_PORT_ON_SUCCESS)))
 527             {
 528                 add_async_completion( async, async->data.apc_context, status, total );
 529             }
 530
 531             if (async->event) set_event( async->event );
 532             else if (async->fd) set_fd_signaled( async->fd, 1 );
 533         }
 534
 535         if (!async->signaled)
 536         {
 537             async->signaled = 1;
 538             wake_up( &async->obj, 0 );
 539         }
 540
 541         async_call_completion_callback( async );
 542
 543         if (async->queue)
 544         {
 545             list_remove( &async->queue_entry );
 546             async_reselect( async );
 547             async->fd = NULL;
 548             async->queue = NULL;
 549             release_object( async );
 550         }
 551     }
 552 }
 553
 554 /* check if an async operation is waiting to be alerted */
 555 int async_waiting( struct async_queue *queue )
 556 {
 557     struct list *ptr;
 558     struct async *async;
 559
 560     if (!(ptr = list_head( &queue->queue ))) return 0;
 561     async = LIST_ENTRY( ptr, struct async, queue_entry );
 562     return !async->terminated;
 563 }
 564
 565 static int cancel_async( struct process *process, struct object *obj, struct thread *thread, client_ptr_t iosb )
 566 {
 567     struct async *async;
 568     int woken = 0;
 569
 570     /* FIXME: it would probably be nice to replace the "canceled" flag with a
 571      * single LIST_FOR_EACH_ENTRY_SAFE, but currently cancelling an async can
 572      * cause other asyncs to be removed via async_reselect() */
 573
 574 restart:
 575     LIST_FOR_EACH_ENTRY( async, &process->asyncs, struct async, process_entry )
 576     {
 577         if (async->terminated || async->canceled) continue;
 578         if ((!obj || (get_fd_user( async->fd ) == obj)) &&
 579             (!thread || async->thread == thread) &&
 580             (!iosb || async->data.iosb == iosb))
 581         {
 582             async->canceled = 1;
 583             fd_cancel_async( async->fd, async );
 584             woken++;
 585             goto restart;
 586         }
 587     }
 588     return woken;
 589 }
 590
 591 void cancel_process_asyncs( struct process *process )
 592 {
 593     cancel_async( process, NULL, NULL, 0 );
 594 }
 595
 596 void cancel_terminating_thread_asyncs( struct thread *thread )
 597 {
 598     struct async *async;
 599
 600 restart:
 601     LIST_FOR_EACH_ENTRY( async, &thread->process->asyncs, struct async, process_entry )
 602     {
 603         if (async->thread != thread || async->terminated || async->canceled) continue;
 604         if (async->completion && async->data.apc_context && !async->event) continue;
 605
 606         async->canceled = 1;
 607         fd_cancel_async( async->fd, async );
 608         goto restart;
 609     }
 610 }
 611
 612 /* wake up async operations on the queue */
 613 void async_wake_up( struct async_queue *queue, unsigned int status )
 614 {
 615     struct list *ptr, *next;
 616
 617     LIST_FOR_EACH_SAFE( ptr, next, &queue->queue )
 618     {
 619         struct async *async = LIST_ENTRY( ptr, struct async, queue_entry );
 620         async_terminate( async, status );
 621         if (status == STATUS_ALERTED) break;  /* only wake up the first one */
 622     }
 623 }
 624
 625 static void iosb_dump( struct object *obj, int verbose );
 626 static void iosb_destroy( struct object *obj );
 627
 628 static const struct object_ops iosb_ops =
 629 {
 630     sizeof(struct iosb),      /* size */
 631     &no_type,                 /* type */
 632     iosb_dump,                /* dump */
 633     no_add_queue,             /* add_queue */
 634     NULL,                     /* remove_queue */
 635     NULL,                     /* signaled */
 636     NULL,                     /* satisfied */
 637     no_signal,                /* signal */
 638     no_get_fd,                /* get_fd */
 639     default_map_access,       /* map_access */
 640     default_get_sd,           /* get_sd */
 641     default_set_sd,           /* set_sd */
 642     no_get_full_name,         /* get_full_name */
 643     no_lookup_name,           /* lookup_name */
 644     no_link_name,             /* link_name */
 645     NULL,                     /* unlink_name */
 646     no_open_file,             /* open_file */
 647     no_kernel_obj_list,       /* get_kernel_obj_list */
 648     no_close_handle,          /* close_handle */
 649     iosb_destroy              /* destroy */
 650 };
 651
 652 static void iosb_dump( struct object *obj, int verbose )
 653 {
 654     assert( obj->ops == &iosb_ops );
 655     fprintf( stderr, "I/O status block\n" );
 656 }
 657
 658 static void iosb_destroy( struct object *obj )
 659 {
 660     struct iosb *iosb = (struct iosb *)obj;
 661
 662     free( iosb->in_data );
 663     free( iosb->out_data );
 664 }
 665
 666 /* allocate iosb struct */
 667 static struct iosb *create_iosb( const void *in_data, data_size_t in_size, data_size_t out_size )
 668 {
 669     struct iosb *iosb;
 670
 671     if (!(iosb = alloc_object( &iosb_ops ))) return NULL;
 672
 673     iosb->status = STATUS_PENDING;
 674     iosb->result = 0;
 675     iosb->in_size = in_size;
 676     iosb->in_data = NULL;
 677     iosb->out_size = out_size;
 678     iosb->out_data = NULL;
 679
 680     if (in_size && !(iosb->in_data = memdup( in_data, in_size )))
 681     {
 682         release_object( iosb );
 683         iosb = NULL;
 684     }
 685
 686     return iosb;
 687 }
 688
 689 /* create an async associated with iosb for async-based requests
 690  * returned async must be passed to async_handoff */
 691 struct async *create_request_async( struct fd *fd, unsigned int comp_flags, const async_data_t *data )
 692 {
 693     struct async *async;
 694     struct iosb *iosb;
 695
 696     if (!(iosb = create_iosb( get_req_data(), get_req_data_size(), get_reply_max_size() )))
 697         return NULL;
 698
 699     async = create_async( fd, current, data, iosb );
 700     release_object( iosb );
 701     if (async)
 702     {
 703         if (!(async->wait_handle = alloc_handle( current->process, async, SYNCHRONIZE, 0 )))
 704         {
 705             release_object( async );
 706             return NULL;
 707         }
 708         async->pending       = 0;
 709         async->direct_result = 1;
 710         async->comp_flags    = comp_flags;
 711     }
 712     return async;
 713 }
 714
 715 struct iosb *async_get_iosb( struct async *async )
 716 {
 717     return async->iosb ? (struct iosb *)grab_object( async->iosb ) : NULL;
 718 }
 719
 720 struct thread *async_get_thread( struct async *async )
 721 {
 722     return async->thread;
 723 }
 724
 725 /* find the first pending async in queue */
 726 struct async *find_pending_async( struct async_queue *queue )
 727 {
 728     struct async *async;
 729     LIST_FOR_EACH_ENTRY( async, &queue->queue, struct async, queue_entry )
 730         if (!async->terminated) return (struct async *)grab_object( async );
 731     return NULL;
 732 }
 733
 734 /* cancels all async I/O */
 735 DECL_HANDLER(cancel_async)
 736 {
 737     struct object *obj = get_handle_obj( current->process, req->handle, 0, NULL );
 738     struct thread *thread = req->only_thread ? current : NULL;
 739
 740     if (obj)
 741     {
 742         int count = cancel_async( current->process, obj, thread, req->iosb );
 743         if (!count && req->iosb) set_error( STATUS_NOT_FOUND );
 744         release_object( obj );
 745     }
 746 }
 747
 748 /* get async result from associated iosb */
 749 DECL_HANDLER(get_async_result)
 750 {
 751     struct iosb *iosb = NULL;
 752     struct async *async;
 753
 754     LIST_FOR_EACH_ENTRY( async, &current->process->asyncs, struct async, process_entry )
 755         if (async->data.user == req->user_arg)
 756         {
 757             iosb = async->iosb;
 758             break;
 759         }
 760
 761     if (!iosb)
 762     {
 763         set_error( STATUS_INVALID_PARAMETER );
 764         return;
 765     }
 766
 767     if (iosb->out_data)
 768     {
 769         data_size_t size = min( iosb->out_size, get_reply_max_size() );
 770         if (size)
 771         {
 772             set_reply_data_ptr( iosb->out_data, size );
 773             iosb->out_data = NULL;
 774         }
 775     }
 776     set_error( iosb->status );
 777 }
 778
 779 /* notify direct completion of async and close the wait handle if not blocking */
 780 DECL_HANDLER(set_async_direct_result)
 781 {
 782     struct async *async = (struct async *)get_handle_obj( current->process, req->handle, 0, &async_ops );
 783     unsigned int status = req->status;
 784
 785     if (!async) return;
 786
 787     if (!async->unknown_status || !async->terminated || !async->alerted)
 788     {
 789         set_error( STATUS_INVALID_PARAMETER );
 790         release_object( &async->obj );
 791         return;
 792     }
 793
 794     if (status == STATUS_PENDING)
 795     {
 796         async->direct_result = 0;
 797         async->pending = 1;
 798     }
 799     else if (req->mark_pending)
 800     {
 801         async->pending = 1;
 802     }
 803
 804     /* if the I/O has completed successfully (or unsuccessfully, and
 805      * async->pending is set), the client would have already set the IOSB.
 806      * therefore, we can do async_set_result() directly and let the client skip
 807      * waiting on wait_handle.
 808      */
 809     async_set_result( &async->obj, status, req->information );
 810
 811     /* close wait handle here to avoid extra server round trip, if the I/O
 812      * either has completed, or is pending and not blocking.
 813      */
 814     if (status != STATUS_PENDING || !async->blocking)
 815     {
 816         close_handle( async->thread->process, async->wait_handle );
 817         async->wait_handle = 0;
 818     }
 819
 820     /* report back to the client whether the wait handle has been closed.
 821      * handle will be 0 if closed by us; otherwise the original value is
 822      * retained
 823      */
 824     reply->handle = async->wait_handle;
 825
 826     release_object( &async->obj );
 827 }