编程技术-IO完成端口原理

IO完成端口原理

内核创建一个KQUEUE，

  fileObject->CompletionContext->Port ==> PKQUEUE;

  fileObject->CompletionContext->Key = 用户自定义的值，可以是buf指针;

typedef struct _KQUEUE {

    DISPATCHER_HEADER Header;

    LIST_ENTRY EntryListHead;      // 已完成IO的IRP List: &irp->Tail.Overlay.ListEntry;

    ULONG CurrentCount;            // 当前运行状态线程数

    ULONG MaximumCount;            // 最大并行线程数(默认等于CPU核心数)

    LIST_ENTRY ThreadListHead;     // 所有调用过GetQueuedCompletionStatus()的线程List

} KQUEUE, *PKQUEUE;

IO完成时：

IopCompleteRequest()

  irp->Tail.CompletionKey = fileObject->CompletionContext->Key;

  KeInsertQueue(PRKQUEUE, PLIST_ENTRY)

      PRKQUEUE = fileObject->CompletionContext->Port; PLIST_ENTRY = &irp->Tail.Overlay.ListEntry;

    KiInsertQueue()

      if (Queue->CurrentCount < Queue->MaximumCount)

        {CurrentCount++; KiReadyThread(Queue->Header.WaitListHead[WaitBlock->Thread]);}

      else

        InsertTailList(&Queue->EntryListHead, Entry);

线程来GetQueuedCompletionStatus()时：

NtRemoveIoCompletion()

  Entry = KeRemoveQueue()

    once: InsertTailList(&Queue->ThreadListHead, Entry);

    if (Queue->CurrentCount < Queue->MaximumCount)

      Entry = RemoveEntryList(Queue->EntryListHead.Flink);

    else

      {CurrentCount--; InsertTailList(&Queue->Header.WaitListHead, &Thread->WaitBlock[0].WaitListEntry); KiSwapThread();}