srv_wakeup

When srv_sleep is used in preemptive mode using a mutex, the corresponding srv_wakeup routine must be preceded by a request for the same mutex. This process ensures that the sleeping thread is ready for srv_wakeup to be executed. The following code fragment shows how srv_wakeup must be preceded by a request for the mutex when it is used in preemptive mode:

/* 

 ** Loop forever, logging language text. srv_getmsg will cause  

 ** this thread to be suspended until a message is available on 

 ** the log_request message queue. 

 */ 

 while((get_status = srv_getmsgq(msgqid, &log_request,  

         SRV_M_WAIT, &info)) == CS_SUCCEED) 

 { 

      /* 

      ** Do the logging here.

     */

     /* 

     ** Request the mutex to make sure the sender 

     ** has called srv_sleep. 

     */ 

     if (WaitForSingleObject(Mutex,INFINITE) != WAIT_OBJECT_0)

             return(CS_FAIL); 

         /* 

         ** Wake up the thread that is waiting for the language  

         ** text to be logged. 

         */ 

         srv_wakeup(log_request, SRV_M_WAKE_FIRST, (CS_VOID*)0, (CS_VOID*)0); 

     /* 

     ** Release the mutex. 

     */ 

     if (!ReleaseMutex(Mutex))

             return(CS_FAIL);

 }