ntoskrnl/ex/resource.c

   1 /* $Id$
   2  *
   3  * COPYRIGHT:       See COPYING in the top level directory
   4  * PROJECT:         ReactOS kernel
   5  * FILE:            ntoskrnl/ex/resource.c
   6  * PURPOSE:         Resource synchronization construct
   7  * PROGRAMMER:      Unknown
   8  * UPDATE HISTORY:
   9  *                  Created 22/05/98
  10  */
  11
  12
  13 /*
  14  * Usage of ERESOURCE members is not documented.
  15  * From names of members and functionnalities, we can assume :
  16  *
  17  * OwnerTable = list of threads who have shared access(if more than one)
  18  * ActiveCount = number of threads who have access to the resource
  19  * Flag = bits : ResourceOwnedExclusive=0x80
  20  *               ResourceNeverExclusive=0x10
  21  *               ResourceReleaseByOtherThread=0x20
  22  *               ResourceDisableBoost=0x08
  23  * SharedWaiters = semaphore, used to manage wait list of shared waiters.
  24  * ExclusiveWaiters = event, used to manage wait list of exclusive waiters.
  25  * OwnerThreads[0]= thread who have exclusive access
  26  * OwnerThreads[1]= if only one thread own the resource
  27  *                     thread who have shared access
  28  *                  else
  29  *                     OwnerThread=0
  30  *                     and TableSize = number of entries in the owner table
  31  * NumberOfExclusiveWaiters = number of threads waiting for exclusive access.
  32  * NumberOfSharedWaiters = number of threads waiting for exclusive access.
  33  *
  34  */
  35
  36 #define ResourceOwnedExclusive 0x80
  37 #define ResourceDisableBoost   0x08
  38
  39 /* INCLUDES *****************************************************************/
  40
  41 #include <ddk/ntddk.h>
  42 #include <internal/ke.h>
  43 #include <internal/pool.h>
  44
  45 #define NDEBUG
  46 #include <internal/debug.h>
  47
  48 /* GLOBALS *******************************************************************/
  49
  50 #define TAG_OWNER_TABLE     TAG('R', 'O', 'W', 'N')
  51 #define TAG_EXCLUSIVE_LOCK  TAG('E', 'R', 'E', 'L')
  52 #define TAG_SHARED_SEM      TAG('E', 'R', 'S', 'S')
  53
  54 /* FUNCTIONS *****************************************************************/
  55
  56
  57 BOOLEAN
  58 STDCALL
  59 ExTryToAcquireResourceExclusiveLite (
  60         PERESOURCE      Resource
  61         )
  62 /*
  63  * FUNCTION: Attempts to require the resource for exclusive access
  64  * ARGUMENTS:
  65  *         Resource = Points to the resource of be acquired
  66  * RETURNS: TRUE if the resource was acquired for the caller
  67  * NOTES: Must be acquired at IRQL < DISPATCH_LEVEL
  68  */
  69 {
  70   return(ExAcquireResourceExclusiveLite(Resource,FALSE));
  71 }
  72
  73 BOOLEAN
  74 STDCALL
  75 ExAcquireResourceExclusive (
  76         PERESOURCE      Resource,
  77         BOOLEAN         Wait
  78         )
  79 {
  80    return(ExAcquireResourceExclusiveLite(Resource,Wait));
  81 }
  82
  83 BOOLEAN
  84 STDCALL
  85 ExAcquireResourceExclusiveLite (
  86         PERESOURCE      Resource,
  87         BOOLEAN         Wait
  88         )
  89 /*
  90  * FUNCTION: Acquires a resource exclusively for the calling thread
  91  * ARGUMENTS:
  92  *       Resource = Points to the resource to acquire
  93  *       Wait = Is set to TRUE if the caller should wait to acquire the
  94  *              resource if it can't be acquired immediately
  95  * RETURNS: TRUE if the resource was acquired,
  96  *          FALSE otherwise
  97  * NOTES: Must be called at IRQL < DISPATCH_LEVEL
  98  */
  99 {
 100    KIRQL oldIrql;
 101
 102    DPRINT("ExAcquireResourceExclusiveLite(Resource %x, Wait %d)\n",
 103           Resource, Wait);
 104
 105    KeAcquireSpinLock(&Resource->SpinLock, &oldIrql);
 106
 107    /* resource already locked */
 108    if((Resource->Flag & ResourceOwnedExclusive)
 109       && Resource->OwnerThreads[0].OwnerThread == ExGetCurrentResourceThread())
 110      {
 111         /* it's ok : same lock for same thread */
 112         Resource->OwnerThreads[0].a.OwnerCount++;
 113         KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 114         DPRINT("ExAcquireResourceExclusiveLite() = TRUE\n");
 115         return(TRUE);
 116      }
 117
 118    if (Resource->ActiveCount && !Wait)
 119      {
 120         KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 121         DPRINT("ExAcquireResourceExclusiveLite() = FALSE\n");
 122         return(FALSE);
 123      }
 124
 125    /*
 126     * This is slightly better than it looks because other exclusive
 127     * threads who are waiting won't be woken up but there is a race
 128     * with new threads trying to grab the resource so we must have
 129     * the spinlock, still normally this loop will only be executed
 130     * once
 131     * NOTE: We might want to set a timeout to detect deadlock
 132     * (10 minutes?)
 133     */
 134    while (Resource->ActiveCount)
 135      {
 136         Resource->NumberOfExclusiveWaiters++;
 137         KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 138         KeWaitForSingleObject(Resource->ExclusiveWaiters,
 139                               Executive,
 140                               KernelMode,
 141                               FALSE,
 142                               NULL);
 143         KeAcquireSpinLock(&Resource->SpinLock, &oldIrql);
 144         Resource->NumberOfExclusiveWaiters--;
 145      }
 146    Resource->Flag |= ResourceOwnedExclusive;
 147    Resource->ActiveCount = 1;
 148    Resource->OwnerThreads[0].OwnerThread = ExGetCurrentResourceThread();
 149    Resource->OwnerThreads[0].a.OwnerCount = 1;
 150    KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 151    DPRINT("ExAcquireResourceExclusiveLite() = TRUE\n");
 152    return(TRUE);
 153 }
 154
 155 static BOOLEAN EiRemoveSharedOwner(PERESOURCE Resource,
 156                                    ERESOURCE_THREAD ResourceThreadId)
 157 /*
 158  * FUNCTION: Removes the current thread from the shared owners of the resource
 159  * ARGUMENTS:
 160  *      Resource = Pointer to the resource for which the thread is to be
 161  *                 added
 162  * NOTE: Must be called with the resource spinlock held
 163  */
 164 {
 165    ULONG i;
 166
 167    if (Resource->OwnerThreads[1].OwnerThread == ResourceThreadId)
 168      {
 169         Resource->OwnerThreads[1].a.OwnerCount--;
 170         if (Resource->OwnerThreads[1].a.OwnerCount == 0)
 171           {
 172              Resource->ActiveCount--;
 173              Resource->OwnerThreads[1].OwnerThread = 0;
 174           }
 175         return(TRUE);
 176      }
 177
 178    if (Resource->OwnerThreads[1].OwnerThread)
 179      {
 180         /* Oh dear, the caller didn't own the resource after all */
 181         return(FALSE);;
 182      }
 183
 184    for (i=0; i<Resource->OwnerThreads[1].a.TableSize; i++)
 185      {
 186         if (Resource->OwnerTable[i].OwnerThread == ResourceThreadId)
 187           {
 188              Resource->OwnerTable[i].a.OwnerCount--;
 189              if (Resource->OwnerTable[i].a.OwnerCount == 0)
 190                {
 191                   Resource->ActiveCount--;
 192                   Resource->OwnerTable[i].OwnerThread = 0;
 193                }
 194              return TRUE;
 195           }
 196      }
 197    return(FALSE);
 198 }
 199
 200 static BOOLEAN EiAddSharedOwner(PERESOURCE Resource)
 201 /*
 202  * FUNCTION: Adds the current thread to the shared owners of the resource
 203  * ARGUMENTS:
 204  *         Resource = Pointer to the resource for which the thread is to be
 205  *                    added
 206  * NOTE: Must be called with the resource spinlock held
 207  */
 208 {
 209    ERESOURCE_THREAD CurrentThread = ExGetCurrentResourceThread();
 210    POWNER_ENTRY freeEntry;
 211    ULONG i = 0;
 212
 213    DPRINT("EiAddSharedOwner(Resource %x)\n", Resource);
 214
 215    if (Resource->ActiveCount == 0)
 216      {
 217         /* no owner, it's easy */
 218         Resource->OwnerThreads[1].OwnerThread = ExGetCurrentResourceThread();
 219         Resource->OwnerThreads[1].a.OwnerCount = 1;
 220         if (Resource->OwnerTable != NULL)
 221           {
 222              ExFreePool(Resource->OwnerTable);
 223           }
 224         Resource->OwnerTable = NULL;
 225         Resource->ActiveCount = 1;
 226         DPRINT("EiAddSharedOwner() = TRUE\n");
 227         return(TRUE);
 228      }
 229
 230    /*
 231     * now, we must search if this thread has already acquired this resource
 232     * then increase ownercount if found, else create new entry or reuse free
 233     * entry
 234     */
 235    if (Resource->OwnerTable == NULL)
 236      {
 237         DPRINT("Creating owner table\n");
 238
 239         /* allocate ownertable,memset to 0, initialize first entry */
 240         Resource->OwnerTable =
 241           ExAllocatePoolWithTag(NonPagedPool, sizeof(OWNER_ENTRY)*3,
 242                                 TAG_OWNER_TABLE);
 243         if (Resource->OwnerTable == NULL)
 244           {
 245              KeBugCheck(0);
 246              return(FALSE);
 247           }
 248         memset(Resource->OwnerTable,0,sizeof(OWNER_ENTRY)*3);
 249         memcpy(&Resource->OwnerTable[0], &Resource->OwnerThreads[1],
 250                sizeof(OWNER_ENTRY));
 251
 252         Resource->OwnerThreads[1].OwnerThread = 0;
 253         Resource->OwnerThreads[1].a.TableSize = 3;
 254
 255         Resource->OwnerTable[1].OwnerThread = CurrentThread;
 256         Resource->OwnerTable[1].a.OwnerCount = 1;
 257         Resource->ActiveCount++;
 258
 259         return(TRUE);
 260      }
 261
 262    DPRINT("Search free entries\n");
 263
 264    DPRINT("Number of entries %d\n",
 265           Resource->OwnerThreads[1].a.TableSize);
 266
 267    freeEntry = NULL;
 268    for (i=0; i<Resource->OwnerThreads[1].a.TableSize; i++)
 269      {
 270         if (Resource->OwnerTable[i].OwnerThread == CurrentThread)
 271           {
 272              DPRINT("Thread already owns resource\n");
 273              Resource->OwnerTable[i].a.OwnerCount++;
 274              return(TRUE);
 275           }
 276         if (Resource->OwnerTable[i].OwnerThread == 0)
 277           {
 278              freeEntry = &Resource->OwnerTable[i];
 279              break;
 280           }
 281      }
 282
 283    DPRINT("Found free entry %x\n", freeEntry);
 284
 285    if (!freeEntry)
 286      {
 287         DPRINT("Allocating new entry\n");
 288
 289         /* reallocate ownertable with one more entry */
 290         freeEntry =
 291           ExAllocatePoolWithTag(NonPagedPool,
 292                                 sizeof(OWNER_ENTRY)*
 293                                 (Resource->OwnerThreads[1].a.TableSize+1),
 294                                 TAG_OWNER_TABLE);
 295         if (freeEntry == NULL)
 296           {
 297              KeBugCheck(0);
 298              return(FALSE);
 299           }
 300         memcpy(freeEntry,Resource->OwnerTable,
 301                sizeof(OWNER_ENTRY)*(Resource->OwnerThreads[1].a.TableSize));
 302         ExFreePool(Resource->OwnerTable);
 303         Resource->OwnerTable=freeEntry;
 304         freeEntry=&Resource->OwnerTable[Resource->OwnerThreads[1].a.TableSize];
 305         Resource->OwnerThreads[1].a.TableSize++;
 306      }
 307    DPRINT("Creating entry\n");
 308    freeEntry->OwnerThread=ExGetCurrentResourceThread();
 309    freeEntry->a.OwnerCount=1;
 310    Resource->ActiveCount++;
 311    return(TRUE);
 312 }
 313
 314 BOOLEAN
 315 STDCALL
 316 ExAcquireResourceSharedLite (
 317         PERESOURCE      Resource,
 318         BOOLEAN         Wait
 319         )
 320 /*
 321  * FUNCTION: Acquires the given resource for shared access by the calling
 322  *           thread
 323  * ARGUMENTS:
 324  *       Resource = Points to the resource to acquire
 325  *       Wait = Is set to TRUE if the caller should be put into wait state
 326  *              until the resource can be acquired if it cannot be acquired
 327  *              immediately
 328  * RETURNS: TRUE, if the resource is acquire
 329  *          FALSE otherwise
 330  */
 331 {
 332    KIRQL oldIrql;
 333
 334    DPRINT("ExAcquireResourceSharedLite(Resource %x, Wait %d)\n",
 335           Resource, Wait);
 336
 337    KeAcquireSpinLock(&Resource->SpinLock, &oldIrql);
 338
 339    /* first, resolve trivial cases */
 340    if (Resource->ActiveCount == 0)
 341      {
 342         EiAddSharedOwner(Resource);
 343         KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 344         DPRINT("ExAcquireResourceSharedLite() = TRUE\n");
 345         return(TRUE);
 346      }
 347
 348    if ((Resource->Flag & ResourceOwnedExclusive)
 349        && Resource->OwnerThreads[0].OwnerThread==ExGetCurrentResourceThread())
 350      {
 351         /* exclusive, but by same thread : it's ok */
 352         /*
 353          * NOTE: Is this correct? Seems the same as ExConvertExclusiveToShared
 354          */
 355         Resource->OwnerThreads[0].a.OwnerCount++;
 356         KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 357         DPRINT("ExAcquireResourceSharedLite() = TRUE\n");
 358         return(TRUE);
 359      }
 360
 361    if ((Resource->Flag & ResourceOwnedExclusive)
 362        || Resource->NumberOfExclusiveWaiters)
 363      {
 364         /* exclusive by another thread , or thread waiting for exclusive */
 365         if (!Wait)
 366           {
 367              KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 368              DPRINT("ExAcquireResourceSharedLite() = FALSE\n");
 369              return(FALSE);
 370           }
 371         else
 372           {
 373             Resource->NumberOfSharedWaiters++;
 374             do
 375             {
 376                /* wait for the semaphore */
 377                KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 378                KeWaitForSingleObject(Resource->SharedWaiters,0, KernelMode, FALSE, NULL);
 379                KeAcquireSpinLock(&Resource->SpinLock, &oldIrql);
 380                /* the spin lock was released we must check again */
 381             }
 382             while ((Resource->Flag & ResourceOwnedExclusive)
 383                 || Resource->NumberOfExclusiveWaiters);
 384             Resource->NumberOfSharedWaiters--;
 385           }
 386      }
 387
 388    EiAddSharedOwner(Resource);
 389    KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 390    DPRINT("ExAcquireResourceSharedLite() = TRUE\n");
 391    return(TRUE);
 392 }
 393
 394 VOID
 395 STDCALL
 396 ExConvertExclusiveToSharedLite (
 397         PERESOURCE      Resource
 398         )
 399 /*
 400  * FUNCTION: Converts a given resource from acquired for exclusive access
 401  *           to acquire for shared access
 402  * ARGUMENTS:
 403  *      Resource = Points to the resource for which the access should be
 404  *                 converted
 405  * NOTES: Caller must be running at IRQL < DISPATCH_LEVEL
 406  */
 407 {
 408    ULONG oldWaiters;
 409    KIRQL oldIrql;
 410
 411    DPRINT("ExConvertExclusiveToSharedLite(Resource %x)\n", Resource);
 412
 413    KeAcquireSpinLock(&Resource->SpinLock, &oldIrql);
 414
 415    oldWaiters = Resource->NumberOfSharedWaiters;
 416
 417    if (!(Resource->Flag & ResourceOwnedExclusive))
 418      {
 419         /* Might not be what the caller expects, better bug check */
 420         KeBugCheck(0);
 421         KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 422         return;
 423      }
 424
 425    //transfer infos from entry 0 to entry 1 and erase entry 0
 426    Resource->OwnerThreads[1].OwnerThread=Resource->OwnerThreads[0].OwnerThread;
 427    Resource->OwnerThreads[1].a.OwnerCount=Resource->OwnerThreads[0].a.OwnerCount;
 428    Resource->OwnerThreads[0].OwnerThread=0;
 429    Resource->OwnerThreads[0].a.OwnerCount=0;
 430    /* erase exclusive flag */
 431    Resource->Flag &= (~ResourceOwnedExclusive);
 432    /* if no shared waiters, that's all */
 433    if (!oldWaiters)
 434      {
 435         KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 436         return;
 437      }
 438    /* else, awake the waiters */
 439    KeReleaseSemaphore(Resource->SharedWaiters,0,oldWaiters,0);
 440    KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 441    DPRINT("ExConvertExclusiveToSharedLite() finished\n");
 442 }
 443
 444 VOID
 445 STDCALL
 446 ExDisableResourceBoostLite (
 447         PERESOURCE      Resource
 448         )
 449 {
 450    Resource->Flag |= ResourceDisableBoost;
 451 }
 452
 453 ULONG
 454 STDCALL
 455 ExGetExclusiveWaiterCount (
 456         PERESOURCE      Resource
 457         )
 458 {
 459   return(Resource->NumberOfExclusiveWaiters);
 460 }
 461
 462 BOOLEAN
 463 STDCALL
 464 ExAcquireSharedStarveExclusive (
 465         PERESOURCE      Resource,
 466         BOOLEAN         Wait
 467         )
 468 /*
 469  * FUNCTION: Acquires a given resource for shared access without waiting
 470  *           for any pending attempts to acquire exclusive access to the
 471  *           same resource
 472  * ARGUMENTS:
 473  *       Resource = Points to the resource to be acquired for shared access
 474  *       Wait = Is set to TRUE if the caller will wait until the resource
 475  *              becomes available when access can't be granted immediately
 476  * RETURNS: TRUE if the requested access is granted. The routine returns
 477  *          FALSE if the input Wait is FALSE and shared access can't be
 478  *          granted immediately
 479  */
 480 {
 481    KIRQL oldIrql;
 482
 483    DPRINT("ExAcquireSharedStarveExclusive(Resource %x, Wait %d)\n",
 484           Resource, Wait);
 485
 486    KeAcquireSpinLock(&Resource->SpinLock, &oldIrql);
 487
 488    /* no owner, it's easy */
 489    if (Resource->ActiveCount == 0)
 490      {
 491         Resource->OwnerThreads[1].OwnerThread=ExGetCurrentResourceThread();
 492         Resource->OwnerThreads[1].a.OwnerCount=1;
 493         Resource->ActiveCount=1;
 494         KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 495         DPRINT("ExAcquireSharedStarveExclusive() = TRUE\n");
 496         return(TRUE);
 497      }
 498
 499    if ((Resource->Flag & ResourceOwnedExclusive)
 500        &&  Resource->OwnerThreads[0].OwnerThread==ExGetCurrentResourceThread())
 501      {
 502         /* exclusive, but by same thread : it's ok */
 503         Resource->OwnerThreads[0].a.OwnerCount++;
 504         KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 505         DPRINT("ExAcquireSharedStarveExclusive() = TRUE\n");
 506         return(TRUE);
 507      }
 508
 509    if (Resource->Flag & ResourceOwnedExclusive)
 510      {
 511         /* exclusive by another thread */
 512         if (!Wait)
 513           {
 514              KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 515              DPRINT("ExAcquireSharedStarveExclusive() = FALSE\n");
 516              return(FALSE);
 517           }
 518         else
 519           {
 520              Resource->NumberOfSharedWaiters++;
 521              /* wait for the semaphore */
 522              KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 523              KeWaitForSingleObject(Resource->SharedWaiters,0,0,0,0);
 524              KeAcquireSpinLock(&Resource->SpinLock, &oldIrql);
 525              Resource->NumberOfSharedWaiters--;
 526           }
 527      }
 528    EiAddSharedOwner(Resource);
 529    KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 530    DPRINT("ExAcquireSharedStarveExclusive() = TRUE\n");
 531    return(TRUE);
 532 }
 533
 534 BOOLEAN
 535 STDCALL
 536 ExAcquireSharedWaitForExclusive (
 537         PERESOURCE      Resource,
 538         BOOLEAN         Wait
 539         )
 540 {
 541   return(ExAcquireResourceSharedLite(Resource,Wait));
 542 }
 543
 544 NTSTATUS
 545 STDCALL
 546 ExDeleteResource (
 547         PERESOURCE      Resource
 548         )
 549 {
 550    return(ExDeleteResourceLite(Resource));
 551 }
 552
 553 NTSTATUS
 554 STDCALL
 555 ExDeleteResourceLite (
 556         PERESOURCE      Resource
 557         )
 558 {
 559    DPRINT("ExDeleteResourceLite(Resource %x)\n", Resource);
 560    if (Resource->OwnerTable) ExFreePool(Resource->OwnerTable);
 561    if (Resource->SharedWaiters) ExFreePool(Resource->SharedWaiters);
 562    if (Resource->ExclusiveWaiters) ExFreePool(Resource->ExclusiveWaiters);
 563    return(STATUS_SUCCESS);;
 564 }
 565
 566 ULONG
 567 STDCALL
 568 ExGetSharedWaiterCount (
 569         PERESOURCE      Resource
 570         )
 571 {
 572    return(Resource->NumberOfSharedWaiters);
 573 }
 574
 575 NTSTATUS
 576 STDCALL
 577 ExInitializeResource (
 578         PERESOURCE      Resource
 579         )
 580 {
 581    return(ExInitializeResourceLite(Resource));
 582 }
 583
 584 NTSTATUS STDCALL
 585 ExInitializeResourceLite (PERESOURCE    Resource)
 586 {
 587    DPRINT("ExInitializeResourceLite(Resource %x)\n", Resource);
 588    memset(Resource,0,sizeof(ERESOURCE));
 589    Resource->NumberOfSharedWaiters = 0;
 590    Resource->NumberOfExclusiveWaiters = 0;
 591    KeInitializeSpinLock(&Resource->SpinLock);
 592    Resource->Flag = 0;
 593    Resource->ExclusiveWaiters =
 594      ExAllocatePoolWithTag(NonPagedPool, sizeof(KEVENT), TAG_EXCLUSIVE_LOCK);
 595    KeInitializeEvent(Resource->ExclusiveWaiters,
 596                      SynchronizationEvent,
 597                      FALSE);
 598    Resource->SharedWaiters =
 599      ExAllocatePoolWithTag(NonPagedPool ,sizeof(KSEMAPHORE), TAG_SHARED_SEM);
 600    KeInitializeSemaphore(Resource->SharedWaiters,0,0x7fffffff);
 601    Resource->ActiveCount = 0;
 602    return(0);
 603 }
 604
 605 BOOLEAN
 606 STDCALL
 607 ExIsResourceAcquiredExclusiveLite (
 608         PERESOURCE      Resource
 609         )
 610 /*
 611  * FUNCTION: Returns whether the current thread has exclusive access to
 612  * a given resource
 613  * ARGUMENTS:
 614  *        Resource = Points to the resource to be queried
 615  * RETURNS: TRUE if the caller has exclusive access to the resource,
 616  *          FALSE otherwise
 617  */
 618 {
 619    return((Resource->Flag & ResourceOwnedExclusive)
 620           && Resource->OwnerThreads[0].OwnerThread==ExGetCurrentResourceThread());
 621 }
 622
 623 ULONG
 624 STDCALL
 625 ExIsResourceAcquiredSharedLite (
 626         PERESOURCE      Resource
 627         )
 628 /*
 629  * FUNCTION: Returns whether the current thread has shared access to a given
 630  *           resource
 631  * ARGUMENTS:
 632  *      Resource = Points to the resource to be queried
 633  * RETURNS: The number of times the caller has acquired shared access to the
 634  *          given resource
 635  */
 636 {
 637    ULONG i;
 638    if (Resource->OwnerThreads[0].OwnerThread == ExGetCurrentResourceThread())
 639      {
 640         return(Resource->OwnerThreads[0].a.OwnerCount);
 641      }
 642    if (Resource->OwnerThreads[1].OwnerThread == ExGetCurrentResourceThread())
 643      {
 644         return(Resource->OwnerThreads[1].a.OwnerCount);
 645      }
 646    if (!Resource->OwnerThreads[1].a.TableSize)
 647      {
 648         return(0);
 649      }
 650    for (i=0; i<Resource->OwnerThreads[1].a.TableSize; i++)
 651      {
 652         if (Resource->OwnerTable[i].OwnerThread==ExGetCurrentResourceThread())
 653           {
 654              return Resource->OwnerTable[i].a.OwnerCount;
 655           }
 656      }
 657    return(0);
 658 }
 659
 660 VOID
 661 STDCALL
 662 ExReinitializeResourceLite (
 663         PERESOURCE      Resource
 664         )
 665 {
 666    Resource->NumberOfSharedWaiters = 0;
 667    Resource->NumberOfExclusiveWaiters = 0;
 668    KeInitializeSpinLock(&Resource->SpinLock);
 669    Resource->Flag=0;
 670    KeInitializeEvent(Resource->ExclusiveWaiters,SynchronizationEvent,
 671                      FALSE);
 672    KeInitializeSemaphore(Resource->SharedWaiters,0,0x7fffffff);
 673    Resource->ActiveCount = 0;
 674    if (Resource->OwnerTable)
 675      {
 676         ExFreePool(Resource->OwnerTable);
 677      }
 678    Resource->OwnerThreads[0].OwnerThread=0;
 679    Resource->OwnerThreads[0].a.OwnerCount=0;
 680    Resource->OwnerThreads[1].OwnerThread=0;
 681    Resource->OwnerThreads[1].a.OwnerCount=0;
 682 }
 683
 684 VOID
 685 FASTCALL
 686 ExReleaseResourceLite (
 687         PERESOURCE      Resource
 688         )
 689 {
 690   return(ExReleaseResourceForThreadLite(Resource,
 691                                         ExGetCurrentResourceThread()));
 692 }
 693
 694 VOID
 695 STDCALL
 696 ExReleaseResourceForThread (
 697         PERESOURCE              Resource,
 698         ERESOURCE_THREAD        ResourceThreadId
 699         )
 700 {
 701   return(ExReleaseResourceForThreadLite(Resource,ResourceThreadId));
 702 }
 703
 704 VOID
 705 STDCALL
 706 ExReleaseResourceForThreadLite (
 707         PERESOURCE              Resource,
 708         ERESOURCE_THREAD        ResourceThreadId
 709         )
 710 /*
 711  * FUNCTION: Releases a resource for the given thread
 712  * ARGUMENTS:
 713  *         Resource = Points to the release to release
 714  *         ResourceThreadId = Identifies the thread that originally acquired
 715  *                            the resource
 716  * NOTES: Must be running at IRQL < DISPATCH_LEVEL
 717  * BUG: We don't support starving exclusive waiters
 718  */
 719 {
 720    KIRQL oldIrql;
 721
 722    DPRINT("ExReleaseResourceForThreadLite(Resource %x, ResourceThreadId %x)\n",
 723           Resource, ResourceThreadId);
 724
 725    KeAcquireSpinLock(&Resource->SpinLock, &oldIrql);
 726
 727    if (Resource->Flag & ResourceOwnedExclusive)
 728      {
 729         DPRINT("Releasing from exclusive access\n");
 730
 731         Resource->OwnerThreads[0].a.OwnerCount--;
 732         if (Resource->OwnerThreads[0].a.OwnerCount > 0)
 733           {
 734              KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 735              DPRINT("ExReleaseResourceForThreadLite() finished\n");
 736              return;
 737           }
 738
 739         Resource->OwnerThreads[0].OwnerThread = 0;
 740         Resource->ActiveCount--;
 741         Resource->Flag &=(~ResourceOwnedExclusive);
 742         assert(Resource->ActiveCount == 0);
 743         DPRINT("Resource->NumberOfExclusiveWaiters %d\n",
 744                Resource->NumberOfExclusiveWaiters);
 745         if (Resource->NumberOfExclusiveWaiters)
 746           {
 747              /* get resource to first exclusive waiter */
 748              KeSetEvent(Resource->ExclusiveWaiters,
 749                         IO_NO_INCREMENT,
 750                         FALSE);
 751              KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 752              DPRINT("ExReleaseResourceForThreadLite() finished\n");
 753              return;
 754           }
 755         DPRINT("Resource->NumberOfSharedWaiters %d\n",
 756                Resource->NumberOfSharedWaiters);
 757         if (Resource->NumberOfSharedWaiters)
 758           {
 759              DPRINT("Releasing semaphore\n");
 760              KeReleaseSemaphore(Resource->SharedWaiters,
 761                                 IO_NO_INCREMENT,
 762                                 Resource->NumberOfSharedWaiters,
 763                                 FALSE);
 764           }
 765         KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 766         DPRINT("ExReleaseResourceForThreadLite() finished\n");
 767         return;
 768      }
 769
 770    EiRemoveSharedOwner(Resource, ResourceThreadId);
 771
 772    if (Resource->ActiveCount == 0)
 773      {
 774         if (Resource->NumberOfExclusiveWaiters)
 775           {
 776              /* get resource to first exclusive waiter */
 777              KeSetEvent(Resource->ExclusiveWaiters,
 778                         IO_NO_INCREMENT,
 779                         FALSE);
 780           }
 781      }
 782
 783    KeReleaseSpinLock(&Resource->SpinLock, oldIrql);
 784    DPRINT("ExReleaseResourceForThreadLite() finished\n");
 785 }
 786
 787
 788 VOID
 789 STDCALL
 790 ExSetResourceOwnerPointer (
 791         IN      PERESOURCE      Resource,
 792         IN      PVOID           OwnerPointer
 793         )
 794 {
 795
 796 }
 797
 798 /* EOF */