天哪,这段代码还是没有看懂

       ...
        IoSetCompletionRoutine(...
                               BulkUsb_IrpCompletionRoutine,
                               &startDeviceEvent,
                                 ...
                               );
        ntStatus = IoCallDriver(stackDeviceObject,
                                Irp);
        if (ntStatus == STATUS_PENDING)
        {
            waitStatus = KeWaitForSingleObject(
                &startDeviceEvent,
                ....
                 );
                ...
        }
              ....
        
        IoCompleteRequest (Irp,
                           IO_NO_INCREMENT
                           );
 各位大哥救命,这是DDK的BulkUSB的bulkpnp.c的一段.我看Walter的书,他说调用IoCallDriver后进入STATUS_PENDING,然后等待startDeviceEvent进入信号态,而startDeviceEvent进入信号态依靠完成例程BulkUsb_IrpCompletionRoutine的设置,而BulkUsb_IrpCompletionRoutine又由IoCompleteRequest调用,但是现在程序正在KeWaitForSingleObject等着,怎么可能运行到下面IoCompletRequest处?我怎么越想越没有想通这个逻辑.
小弟先谢过了.

IoCallDriver()会调用下层driver,当下层的driver发现设备没准备好时,会返回status_pending.你的KeWaitForSingleObject()就会等待
随着时间的流逝当下层的driver发现设备准备好时,就会调用IoCompleteRequest();你的completeroutine就会获得调用

(引用masmasm兄)
随着时间的流逝当下层的driver发现设备准备好时,就会调用IoCompleteRequest();你的completeroutine就会获得调用

有劳各位老兄,我就是没有看懂那段代码如何调用IoCompleteRequest,如果从KeWaitSingleObject顺序执行下来倒是可以理解,但是现在KeWaitSingleObject自己还在等着IoCompleteRequest调用完成例程BulkUsb_IrpCompletionRoutine来设置事件startDeviceEvent为信号态啊.不会是设备跳过KeWaitSingleObject自己就直接调用了IoCompleteRequest吧?不好意思,我很菜,再次请教.

（1） IoCallDriver()调用下层driver,并返回status_pending.
IoCallDriver sends an IRP to the next-lower-level driver after the caller has set up the I/O stack location in the IRP for that driver.IoCallDriver returns the NTSTATUS value that a lower driver set in the I/O status block for the given request or STATUS_PENDING if the request was queued for additional processing.
（2）KeWaitForSingleObject()等待。
（3）当下层的driver完成IRP，就会调BulkUsb_IrpCompletionRoutine。
CompletionRoutine - Address of the completion routine that is to be invoked once the next level driver completes the packet.
（4）KeWaitForSingleObject受信，运行到下面IoCompletRequest处.
KeWaitForSingleObject routine puts the current thread into a wait state until the given dispatcher object is set to a signaled state or (optionally) until the wait times out.

多谢两位回帖,但是我还是没有搞懂完成例程是怎么调用的,从unknow兄的帖子来看应该是IRP在下层设备完成后就自动调用了,但是我看Walter的书说
IoCompleteRequest is responsible for calling all of the completion routines that drivers installed in their respective stack locations. ... is this: Something calls IoCompleteRequest to signal the end of processing for the IRP.
但是Unknow的意思是先调用完成例程,然后调用IoCompleteRequest?
不好意思,小弟实在愚笨,再次请教.

设备底层的驱动程序完成IRP后，调用IoCompleteRequest,Irp沿设备
栈向上传递，若设有完成列程，就调用完成列程，在完成列程中，若
返回码是STATUS_MORE_PROCESSING_REQUESTED，则避免进一步处理。
否则，继续沿设备栈向上，同理处理，只到返回原始的调用者。
IoCompleteRequest is responsible for calling all of the completion routines（栈中每层都可以设完成列程） that drivers installed in their respective stack locations. ... is this: Something calls IoCompleteRequest to signal the end of processing for the IRP.