/* pipe_close.c  -  pipe_close */

#include 

/*------------------------------------------------------------------------
 * pipe_close  -  Close a pipe
 *------------------------------------------------------------------------
*/

devcall pipe_close (
          struct dentry *devptr         /* Entry in device switch table */
        )
{
        struct  pipecblk *piptr;        /* Pointer to pipe control block*/

        /* Note: because both a writing process and reading process use */
        /*  a given pipe, both will close the pipe.  Conceptually, the  */
        /*  first call moves the pipe to a read-only state and marks the*/
        /*  end-of-ile. The second call deallocates the pipe device,    */
        /*  making it available for reuse.                              */

        piptr = &pipetab[devptr->dvminor];

        /* If pipe is completely closed, return SYSERR */

        if (piptr->pstate == PIPE_FREE) {
                return SYSERR;
        }

        /* First call to close -- move to EOF state */

        if (piptr->pstate == PIPE_OPEN) {
                piptr->pstate = PIPE_EOF;
                resched_cntl(DEFER_START);
                if (semcount(piptr->pcsem) < 0) {
                        /* Pipe is empty and consumer is blocked, so    */
                        /* Allow the consumer to run                    */
                        semreset(piptr->pcsem, 0);
                }

                /* Allow a blocked producer to proceed, if any */

                if (semcount(piptr->ppsem) < 0) {
                        semreset(piptr->ppsem, 0);
                }
                resched_cntl(DEFER_STOP);
                return OK;
        }

        /* Second call to close - deallocate the pipe device */

        piptr->pstate = PIPE_FREE;
        semdelete(piptr->ppsem);
        semdelete(piptr->pcsem);
        piptr->pavail = 0;
        return OK;
}