Windows Driver Model >> C/C++ >> Synchronization

Mutex

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參考資訊：
1. Source Code

Mutex是一個互斥的機制，有點類似Spin Lock，當有CPU取得Mutex後，其餘CPU會處於Wait狀態，而相較於Spin Lock，Mutex並不會讓CPU處於忙碌的狀態，也不會提升到DISPATCH_LEVEL，是一個相當適合用來做序列化的機制，使用步驟如下：
1. KeInitializeMutex()
2. KeWaitForSingleObject()
3. KeReleaseMutex()

main.c

#include <wdm.h>

#define DEV_NAME L"\\Device\\MyDriver"
#define SYM_NAME L"\\DosDevices\\MyDriver"

#define MAX_THREAD 3

KMUTEX myMutex={0};
PVOID pThread[MAX_THREAD]={0};
PDEVICE_OBJECT pNextDevice=NULL;

void MyThread(PVOID pParam)
{
  int t=(int)pParam;
  NTSTATUS status=0;
  LARGE_INTEGER stTime;
 
  stTime.HighPart|= -1;
  stTime.LowPart = -10000000;
  DbgPrint("Thread%d, Acquiring Mutex", t);
  status = KeWaitForSingleObject(&myMutex, Executive, KernelMode, FALSE, NULL);
  DbgPrint("Thread%d, Acquired Mutex", t);
  DbgPrint("Thread%d, Sleeping", t);
  KeDelayExecutionThread(KernelMode, FALSE, &stTime);
  DbgPrint("Thread%d, Releasing Mutex", t);
  KeReleaseMutex(&myMutex, FALSE);
  DbgPrint("Thread%d, Released Mutex", t);
  PsTerminateSystemThread(STATUS_SUCCESS);
}

NTSTATUS AddDevice(PDRIVER_OBJECT pOurDriver, PDEVICE_OBJECT pPhyDevice)
{
  PDEVICE_OBJECT pOurDevice=NULL;
  UNICODE_STRING usDeviceName;
  UNICODE_STRING usSymboName;

  RtlInitUnicodeString(&usDeviceName, DEV_NAME);
  IoCreateDevice(pOurDriver, 0, &usDeviceName, FILE_DEVICE_UNKNOWN, 0, FALSE, &pOurDevice);
  RtlInitUnicodeString(&usSymboName, SYM_NAME);
  IoCreateSymbolicLink(&usSymboName, &usDeviceName);
  pNextDevice = IoAttachDeviceToDeviceStack(pOurDevice, pPhyDevice);
  pOurDevice->Flags&= ~DO_DEVICE_INITIALIZING;
  pOurDevice->Flags|= DO_BUFFERED_IO;
  return STATUS_SUCCESS;
}

void Unload(PDRIVER_OBJECT pOurDriver)
{
  pOurDriver = pOurDriver;
}

NTSTATUS IrpPnp(PDEVICE_OBJECT pOurDevice, PIRP pIrp)
{
  int cc=0;
  UNICODE_STRING usSymboName={0};
  PIO_STACK_LOCATION psk = IoGetCurrentIrpStackLocation(pIrp);

  if(psk->MinorFunction == IRP_MN_REMOVE_DEVICE){
    for(cc=0; cc<MAX_THREAD; cc++){
      if(pThread[cc] != NULL){
        KeWaitForSingleObject(pThread[cc], Executive, KernelMode, FALSE, NULL);
        ObDereferenceObject(pThread[cc]);
      }
    }
    RtlInitUnicodeString(&usSymboName, SYM_NAME);
    IoDeleteSymbolicLink(&usSymboName);
    IoDetachDevice(pNextDevice);
    IoDeleteDevice(pOurDevice);
  }
  IoSkipCurrentIrpStackLocation(pIrp);
  return IoCallDriver(pNextDevice, pIrp);
}

NTSTATUS DriverEntry(PDRIVER_OBJECT pOurDriver, PUNICODE_STRING pOurRegistry)
{
  int cc=0;
  HANDLE hThread=0;
  NTSTATUS status=0;

  pOurDriver->MajorFunction[IRP_MJ_PNP] = IrpPnp;
  pOurDriver->DriverExtension->AddDevice = AddDevice;
  pOurDriver->DriverUnload = Unload;

  KeInitializeMutex(&myMutex, 0);
  for(cc=0; cc<MAX_THREAD; cc++){
    status = PsCreateSystemThread(&hThread, THREAD_ALL_ACCESS, NULL, (PHANDLE)-1, NULL, MyThread, (PVOID)cc);
    if(status == STATUS_SUCCESS){
      ObReferenceObjectByHandle(hThread, THREAD_ALL_ACCESS, NULL, KernelMode, &pThread[cc], NULL);
      ZwClose(hThread);
    }
  }
  return STATUS_SUCCESS;
}

DriverEntry()產生3個Thread，每個Thread會嘗試取得Mutex，一旦取得Mutex後，會延遲一秒後才釋放Mutex，達到一次只能有一個CPU執行的效果

結果

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