很多时候Irp被送到底层驱动程序后, 由于硬件设备的问题, Irp不能够得到及时的处理, 甚至有可能永远都不会被处理.这时候需要对Irp超时情况作出处理, 一旦在规定时间内Irp没有被处理, 操作系统就会进入到Irp的超时处理函数中.
在驱动程序编程中, 经常遇到一种情况, 对某一设备的操作很久没有反应, 如果在规定时间内没有完成操作, 则要取消该操作, 取消例程需要程序员发出取消命令. 如在应用程序中执行CancelIo Win32 api函数, 或者在驱动程序中执行IoCanceIrp内核函数.当然也可以设置Irp超时, 当Irp超时后, 操作系统页会取消Irp. 从而进入Irp的取消例程.
动作是这样的, 首先初始化一个定时器对象和一个Dpc对象, 并将Dpc例程和定时器对象进行关联, 在每次对Irp操作前.开启定时器, 并设置好一定时间的超时. 如果在指定时间内对irp的处理没有结束. 那么操作系统就会进入Dpc例程.还有如果驱动程序能在超时前结束Irp的操作. 则应该取消定时器. 从而保证不会再次取消Irp.
下面这个代码对写入超时处理, 为了演示超时的效果. 在Irp_Mj_Write中直接在派遣函数中直接返回Pending.这样Irp就永远不会被结束了. 在超时到了, 就会进入超时处理函数. 在超时处理函数中Irp被超时结束. 当然也打印了一下.
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/* Windows 内核下Irp超时处理 3环代码
编译方法参见makefile. TAB = 8
*/
#include <windows.h>
#include <stdio.h>
#pragma comment( linker, "/Entry:Jmain" )
#pragma comment( linker, "/subsystem:console" )
#define DEVICE_NAME "\\\\.\\SysLinkTimeOut"
//===========================================================================
//用户层入口
//===========================================================================
int Jmain() {
CHAR cBuf\[10\];
BOOL bRet;
DWORD dwByteWrite;
HANDLE hDevice = INVALID_HANDLE_VALUE;
OVERLAPPED StOverLapped = {0};
do {
//异步打开设备
hDevice = CreateFile( DEVICE_NAME, GENERIC_READ | GENERIC_WRITE,
0, NULL, OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, NULL );
if ( hDevice == INVALID_HANDLE_VALUE ) {
printf( "打开设备驱动失败!\n" );
break;
}
RtlFillMemory(cBuf, sizeof( cBuf ), 'a' );
bRet = WriteFile( hDevice, cBuf, sizeof( cBuf ), &dwByteWrite, &StOverLapped );
if ( !bRet ) {
printf ( "写入设备失败!\n" ) ;
break;
}
} while ( FALSE );
if ( hDevice != INVALID_HANDLE_VALUE ) {
CloseHandle( hDevice );
}
system( "pause" );
return 0;
}
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这边是内核的代码:
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/* Windows 内核下Irp超时处理 0环代码
编译方法参见makefile. TAB = 8
*/
#include <ntddk.h>
#define DEVICE_NAME L"\\Device\\DevTimeOut"
#define SYSLINK_NAME L"\\??\\SysLinkTimeOut"
typedef struct tagDevice_Ext {
PIRP pIrp;
KDPC StDpc; //Dpc对象
KTIMER StTimer; //计时器对象
PDEVICE_OBJECT pDevice;
UNICODE_STRING USzDeviceName;
UNICODE_STRING USzSysLinkName;
} DEVICE_EXT, *PDEVICE_EXT;
//===========================================================================
//驱动卸载例程
//===========================================================================
VOID DriverUnload( PDRIVER_OBJECT pDriverObj ) {
PDEVICE_EXT pDeviceExt = NULL;
PDEVICE_OBJECT pNextDeviceObj = NULL;
pNextDeviceObj = pDriverObj->DeviceObject;
while ( pNextDeviceObj != NULL ) {
pDeviceExt = pNextDeviceObj->DeviceExtension;
IoDeleteDevice( pDeviceExt->pDevice );
IoDeleteSymbolicLink( &pDeviceExt->USzSysLinkName );
KdPrint( ( "删除%wZ成功!\n", &pDeviceExt->USzDeviceName ) );
pNextDeviceObj = pNextDeviceObj->NextDevice;
}
}
//===========================================================================
//所有不关心的Irp
//===========================================================================
NTSTATUS DispatchRoutine( PDEVICE_OBJECT pDeviceObj, PIRP pIrp ) {
pIrp->IoStatus.Information = 0;
pIrp->IoStatus.Status = STATUS_SUCCESS;
IoCompleteRequest( pIrp, IO_NO_INCREMENT );
return STATUS_SUCCESS;
}
//===========================================================================
//写入请求处理
//===========================================================================
NTSTATUS DispatchWrite( PDEVICE_OBJECT pDeviceObj, PIRP pIrp ) {
LARGE_INTEGER liTimeOut;
PDEVICE_EXT pDeviceExt = NULL;
pDeviceExt = pDeviceObj->DeviceExtension;
ASSERT( pDeviceExt != NULL );
//将当前Irp挂起
IoMarkIrpPending( pIrp );
pDeviceExt->pIrp = pIrp;
//定义3S超时
liTimeOut = RtlConvertLongToLargeInteger( -10 * 3000 * 10 );
//开启定时器, 3秒后Irp返回失败, 这里肯定是返回失败了!
//如果驱动程序能够超时前结束Irp的操作, 则应该取消定时器从而保证
//不会被操作系统再次取消Irp
KeSetTimer( &pDeviceExt->StTimer, liTimeOut, &pDeviceExt->StDpc );
return STATUS_PENDING;
}
//===========================================================================
//3秒DPC 取消例程
//===========================================================================
#pragma code_seg( )
VOID OnTimerDpc( PKDPC pDpc, PVOID pContext, PVOID SysArg1, PVOID SysArg2 ) {
PIRP pIrp = NULL;
ULONG ulWriteLen, i;
PUCHAR pBuf = NULL;
PDEVICE_EXT pDeviceExt = NULL;
PDEVICE_OBJECT pDeviceObj = NULL;
PIO_STACK_LOCATION Stack = NULL;
PAGED_CODE_LOCKED();
pDeviceExt = ( ( PDEVICE_OBJECT )pContext )->DeviceExtension;
pIrp = pDeviceExt->pIrp;
Stack = IoGetCurrentIrpStackLocation( pIrp );
ulWriteLen = Stack->Parameters.Write.Length;
pBuf = pIrp->AssociatedIrp.SystemBuffer;
for( i = 0; i < 10; i++ ) {
KdPrint( ( "%c\t", *( pBuf + i ) ) );
}
KdPrint( ( "\n" ) );
//取消IRP, Win32那边会返回失败!
pIrp->IoStatus.Information = 0;
pIrp->IoStatus.Status = STATUS_CANCELLED;
IoCompleteRequest( pIrp, IO_NO_INCREMENT );
}
//===========================================================================
//驱动入口
//===========================================================================
NTSTATUS DriverEntry( PDRIVER_OBJECT pDriverObj, PUNICODE_STRING pUSzRegPath ) {
NTSTATUS Status;
ULONG i;
PDEVICE_EXT pDeviceExt = NULL;
PDEVICE_OBJECT pDevice = NULL;
UNICODE_STRING USzDeviceName = RTL_CONSTANT_STRING( DEVICE_NAME );
UNICODE_STRING USzSysLinkName = RTL_CONSTANT_STRING( SYSLINK_NAME );
Status = IoCreateDevice( pDriverObj, sizeof( DEVICE_EXT ), &USzDeviceName,
FILE_DEVICE_UNKNOWN, 0, TRUE, &pDevice );
if ( !NT_SUCCESS( Status ) ) {
KdPrint( ( "设备创建失败!\n" ) );
return Status;
}
Status = IoCreateSymbolicLink( &USzSysLinkName, &USzDeviceName );
if ( !NT_SUCCESS( Status ) ) {
KdPrint( ( "设备链接创建失败!\n" ) );
return Status;
}
pDevice->Flags |= DO_BUFFERED_IO;
pDeviceExt = pDevice->DeviceExtension;
pDeviceExt->pDevice = pDevice;
pDeviceExt->USzDeviceName = USzDeviceName;
pDeviceExt->USzSysLinkName = USzSysLinkName;
//初始化定时器对象, Dpc对象
KeInitializeTimer( &pDeviceExt->StTimer );
KeInitializeDpc( &pDeviceExt->StDpc, &OnTimerDpc, pDevice );
for( i = 0; i < IRP_MJ_MAXIMUM_FUNCTION; i++ ) {
pDriverObj->MajorFunction\[i\] = &DispatchRoutine;
}
pDriverObj->DriverUnload = &DriverUnload;
pDriverObj->MajorFunction\[IRP_MJ_WRITE\] = &DispatchWrite;
return Status;
}
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