reactos操作系统实现(38)

由于Reactos是以线程为最小的调度单位，如果仅仅创建进程的数据结构，不足以运行进程的任务，每个进程至少需要一个线程才可以运行，下面就来分析系统进程的线程创建，代码如下：

#195      /* Setup the system initialization thread */

#196      Status = PsCreateSystemThread(&SysThreadHandle,

#197                                    THREAD_ALL_ACCESS,

#198                                    &ObjectAttributes,

#199                                    0,

#200                                    NULL,

#201                                    Phase1Initialization,

#202                                    LoaderBlock);

#203      if (!NT_SUCCESS(Status)) return FALSE;

#204 

这段代码里是调用函数PsCreateSystemThread来创建一个系统的线程。

#001  /*

#002   * @implemented

#003   */

#004  NTSTATUS

#005  NTAPI

#006  PsCreateSystemThread(OUT PHANDLE ThreadHandle,

#007                       IN ACCESS_MASK DesiredAccess,

#008                       IN POBJECT_ATTRIBUTES ObjectAttributes,

#009                       IN HANDLE ProcessHandle,

#010                       IN PCLIENT_ID ClientId,

#011                       IN PKSTART_ROUTINE StartRoutine,

#012                       IN PVOID StartContext)

#013  {

设置目标进程为空。

#014      PEPROCESS TargetProcess = NULL;

保存了进程句柄。

#015      HANDLE Handle = ProcessHandle;

#016      PAGED_CODE();

#017      PSTRACE(PS_THREAD_DEBUG,

#018              "ProcessHandle: %p StartRoutine: %p StartContext: %p/n",

#019              ProcessHandle, StartRoutine, StartContext);

#020 

检查进程句柄是否为空，如果为空，就是系统进程的线程，否则是用户进程的线程。

#021      /* Check if we have a handle. If not, use the System Process */

#022      if (!ProcessHandle)

#023      {

#024          Handle = NULL;

#025          TargetProcess = PsInitialSystemProcess;

#026      }

#027 

这里调用共享函数PspCreateThread来创建线程。

#028      /* Call the shared function */

#029      return PspCreateThread(ThreadHandle,

#030                             DesiredAccess,

#031                             ObjectAttributes,

#032                             Handle,

#033                             TargetProcess,

#034                             ClientId,

#035                             NULL,

#036                             NULL,

#037                             FALSE,

#038                             StartRoutine,

#039                             StartContext);

#040  }

通过上面代码可以看到，最终调用函数PspCreateThread创建一个线程。