reactos/hal/halppc/generic/fmutex.c

   1 /*
   2  * COPYRIGHT:       See COPYING in the top level directory
   3  * PROJECT:         ReactOS HAL
   4  * FILE:            ntoskrnl/hal/x86/fmutex.c
   5  * PURPOSE:         Deprecated HAL Fast Mutex
   6  * PROGRAMMERS:     Alex Ionescu (alex@relsoft.net)
   7  */
   8
   9 /*
  10  * NOTE: Even HAL itself has #defines to use the Exi* APIs inside NTOSKRNL.
  11  *       These are only exported here for compatibility with really old
  12  *       drivers. Also note that in theory, these can be made much faster
  13  *       by using assembly and inlining all the operations, including
  14  *       raising and lowering irql.
  15  */
  16
  17 /* INCLUDES *****************************************************************/
  18
  19 #include <hal.h>
  20 #define NDEBUG
  21 #include <debug.h>
  22
  23 #undef ExAcquireFastMutex
  24 #undef ExReleaseFastMutex
  25
  26 /* FUNCTIONS *****************************************************************/
  27
  28 VOID
  29 FASTCALL
  30 ExAcquireFastMutex(PFAST_MUTEX FastMutex)
  31 {
  32     KIRQL OldIrql;
  33
  34     /* Raise IRQL to APC */
  35     KeRaiseIrql(APC_LEVEL, &OldIrql);
  36
  37     /* Decrease the count */
  38     if (InterlockedDecrement(&FastMutex->Count))
  39     {
  40         /* Someone is still holding it, use slow path */
  41         FastMutex->Contention++;
  42         KeWaitForSingleObject(&FastMutex->Event,
  43                               WrExecutive,
  44                               KernelMode,
  45                               FALSE,
  46                               NULL);
  47     }
  48
  49     /* Set the owner and IRQL */
  50     FastMutex->Owner = KeGetCurrentThread();
  51     FastMutex->OldIrql = OldIrql;
  52 }
  53
  54 VOID
  55 FASTCALL
  56 ExReleaseFastMutex(PFAST_MUTEX FastMutex)
  57 {
  58     KIRQL OldIrql;
  59
  60     /* Erase the owner */
  61     FastMutex->Owner = (PVOID)1;
  62     OldIrql = FastMutex->OldIrql;
  63
  64     /* Increase the count */
  65     if (InterlockedIncrement(&FastMutex->Count) <= 0)
  66     {
  67         /* Someone was waiting for it, signal the waiter */
  68         KeSetEventBoostPriority(&FastMutex->Event, IO_NO_INCREMENT);
  69     }
  70
  71     /* Lower IRQL back */
  72     KeLowerIrql(OldIrql);
  73 }
  74
  75 BOOLEAN
  76 FASTCALL
  77 ExiTryToAcquireFastMutex(PFAST_MUTEX FastMutex)
  78 {
  79     KIRQL OldIrql;
  80
  81     /* Raise to APC_LEVEL */
  82     KeRaiseIrql(APC_LEVEL, &OldIrql);
  83
  84     /* Check if we can quickly acquire it */
  85     if (InterlockedCompareExchange(&FastMutex->Count, 0, 1) == 1)
  86     {
  87         /* We have, set us as owners */
  88         FastMutex->Owner = KeGetCurrentThread();
  89         FastMutex->OldIrql = OldIrql;
  90         return TRUE;
  91     }
  92     else
  93     {
  94         /* Acquire attempt failed */
  95         KeLowerIrql(OldIrql);
  96         return FALSE;
  97     }
  98 }
  99
 100 /* EOF */