xinu: Desktop/xinu_mips-1.0.2.tar/xinu_mips-1.0.2/system/receive.c Source File

00001 
00007 /* Embedded XINU, Copyright (C) 2007.  All rights reserved. */
00008 
00009 #include <kernel.h>
00010 #include <device.h>
00011 #include <proc.h>
00012 
00019 syscall receive(bool block)
00020 {
00021         irqmask ps;    
00022         pcb   *ppcb;
00023         ulong msg;
00024 
00025         ps = disable();
00026         ppcb = &proctab[currpid];
00027         if ( !ppcb->hasmsg ) 
00028         {
00029                 if ( BLOCK == block )      /* if no message, block               */
00030                 {
00031                         ppcb->state = PRRECV;  /* change state from PRCURR to PRRECV */
00032                         resched();             /* reschedule                         */
00033                 }
00034                 else                       /* if no message, return NULL         */
00035                 {
00036                         restore(ps);
00037                         return NULL;
00038                 }
00039         }
00040         msg = ppcb->msg;                       /* retrieve message                   */
00041         ppcb->hasmsg = FALSE;          /* reset mailbox                      */
00042         restore(ps);
00043         return msg;
00044 }