scs_msg.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

     *
     * Pending explicit SCS extensions of send credits are aborted whenever
     * there are no longer any send credits to extend.
     *
     * NOTE: The maximum number of send credits may not be decreased below the
     *	     remote SYSAP's minimum send credit requirement.  In addition, it
     *       may not be decreased by more then the current number of send
     *	     credits pending extension across the connection.
     */
    Check_connid2( csb->connid, cbvte, cb )
    if( cb->cinfo.cstate != CS_OPEN ) {
	status = RET_INVCSTATE;
    } else if( csb->Ncredits > 0 ) {
	for( ;
	     csb->Ncredits > 0;
	     ++cb->cinfo.init_rec_credit,
	     ++cb->cinfo.pend_rec_credit,
	     --csb->Ncredits ) {
	    if(( scsbp = ( *cb->Alloc_msg )( cb->pccb ))) {
		( void )( *cb->Add_msg )( cb->pccb, scsbp );
	    } else {
		break;
	    }
	}
	if( cb->cinfo.cbstate == CB_NOT_WAIT  &&
	     cb->cinfo.pend_rec_credit        &&
	     cb->cinfo.rec_credit < ( cb->cinfo.min_rec_credit + scs_cushion)){
	    ( void )scs_request( CB_CREDIT_PEND, cb, cb->pb, NULL );
	}
    } else if( csb->Ncredits < 0 ) {
	for( ;
	     ( csb->Ncredits < 0	 &&
	       cb->cinfo.pend_rec_credit &&
	       cb->cinfo.min_rec_credit < cb->cinfo.init_rec_credit );
	     ++csb->Ncredits,
	     --cb->cinfo.pend_rec_credit,
	     --cb->cinfo.init_rec_credit ) {
	    if(( scsbp = ( *cb->Remove_msg )( cb->pccb ))) {
		( void )( *cb->Dealloc_msg )( cb->pccb, scsbp );
	    } else {
		break;
	    }
	}
	if( cb->cinfo.pend_rec_credit == 0 ) {
	    Remove_pb_waitq( cb )
	}
    }
    csb->Ncredits = cb->cinfo.init_rec_credit;
    Unlock_cbvte( cbvte );
    Unlock_scadb();
    return( status );
}

/*   Name:	scs_add_credit	- Add back Reserved Send Credit
 *
 *   Abstract:	This function adds back a send credit previously reserved by a
 *		SYSAP for emergency communication across a specific logical SCS
 *		connection.
 *
 *   Inputs:
 *
 *   IPL_SCS			- Interrupt processor level
 *   csb			- Communication Services Block pointer
 *	connid			-  Identification of logical SCS connection
 *   lscs			- Local system permanent information
 *   scs_cbvtdb			- CB vector table database pointer
 *
 *   Outputs:
 *
 *   IPL_SCS			- Interrupt processor level
 *   cb				- Connection Block pointer
 *	cinfo.reserved_credit	-  Number of credits reserved by SYSAP
 *	cinfo.snd_credit	-  Number of send credits
 *
 *   Return Values:
 *
 *   RET_SUCCESS		- Successfully added back reserved send credit
 *   RET_INVCONNID		- Invalid connection identification number
 *   RET_INVCSTATE		- Connection in invalid state
 *   RET_NOCREDITS		- No send credits available to add back
 *
 *   SMP:	The CB is locked to synchronize access and prevent deletion.
 *		It is indirectly locked through its CBVTE.
 */
u_long
scs_add_credit( csb )
    CSB			*csb;
{
    register CB		*cb;
    register CBVTE	*cbvte;
    register u_long	status = RET_SUCCESS;

    /* The steps involved in adding back a reserved send credit are as follows:
     *
     * 1. Lock and retrieve the CB.
     * 2. Add back a reserved send credit.
     * 3. Unlock the CB.
     * 4. Return an appropriate status.
     */
    Check_connid( csb->connid, cbvte, cb )
    if( cb->cinfo.cstate != CS_OPEN ) {
	status = RET_INVCSTATE;
    } else if( cb->cinfo.reserved_credit > 0 ) {
	--cb->cinfo.reserved_credit;
	++cb->cinfo.snd_credit;
    } else {
	status = RET_NOCREDITS;
    }
    Unlock_cbvte( cbvte );
    return( status );
}

/*   Name:	scs_rsv_credit	- Reserve Send Credit for Emergency Use
 *
 *   Abstract:	This function withdraws a send credit from a specific logical
 *		SCS connection and reserves it for emergency communication.
 *		The lack of send credits prevents such reservation.  The SYSAP
 *		is notified of send credit availability through asynchronous
 *		invocation of the connection's control event routine.
 *
 *   Inputs:
 *
 *   IPL_SCS			- Interrupt processor level
 *   csb			- Communication Services Block pointer
 *	connid			-  Identification of logical SCS connection
 *   lscs			- Local system permanent information
 *   scs_cbvtdb			- CB vector table database pointer
 *
 *   Outputs:
 *
 *   IPL_SCS			- Interrupt processor level
 *   cb				- Connection Block pointer
 *	cinfo.reserved_credit	-  Number of credits reserved by SYSAP
 *	cinfo.snd_credit	-  Number of send credits
 *	cinfo.status.cwait	-  SYSAP waiting for send credits flag
 *
 *   Return Values:
 *
 *   RET_SUCCESS		- Successfully reserved send credit
 *   RET_INVCONNID		- Invalid connection identification number
 *   RET_INVCSTATE		- Connection in invalid state
 *   RET_NOCREDITS		- No send credits available to reserve
 *
 *   SMP:	The CB is locked to synchronize access and prevent deletion.
 *		It is indirectly locked through its CBVTE.
 */
u_long
scs_rsv_credit( csb )
    CSB			*csb;
{
    register CB		*cb;
    register CBVTE	*cbvte;
    register u_long	status = RET_SUCCESS;

    /* The steps involved in reserving a send credit for emergency use are as
     * follows:
     *
     * 1. Lock and retrieve the CB.
     * 2. Withdraw and reserve a send credit.
     * 3. Unlock the CB.
     * 4. Return an appropriate status.
     *
     * Remember the lack of send credits on the connection.  The SYSAP is
     * notified when credits are again available.  
     */
    Check_connid( csb->connid, cbvte, cb )
    if( cb->cinfo.cstate != CS_OPEN ) {
	status = RET_INVCSTATE;
    } else if( cb->cinfo.snd_credit > 0 ) {
	--cb->cinfo.snd_credit;
	++cb->cinfo.reserved_credit;
    } else {
	cb->cinfo.status.cwait = 1;
	status = RET_NOCREDITS;
    }
    Unlock_cbvte( cbvte );
    return( status );
}

/*   Name:	scs_send_msg	- Send Application Sequenced Message
 *
 *   Abstract:	This function initiates transmission of an application
 *		sequenced message over a specific logical SCS connection.  Two
 *		options exist for disposal of the buffer following
 *		transmission:
 *
 *		1. Convert the buffer into a receive message buffer.
 *		2. Deallocate the buffer.
 *
 *		A send credit is exhausted.  The lack of send credits prevents
 *		application sequenced message transmission.  The SYSAP is
 *		notified of send credit availability through asynchronous
 *		invocation of the connection's control event routine.
 *
 *		As pending send credits are piggy backed on the application
 *		sequenced message any pending explicit send credit extension
 *		is aborted.
 *
 *
 *   Inputs:
 *
 *   IPL_SCS			- Interrupt processor level
 *   csb			- Communication Services Block pointer
 *	buf			-  Address of application data buffer
 *	connid			-  Identification of logical SCS connection
 *	ov3.disposal		-  Disposition of sent buffer
 *	size			-  Application data transfer size
 *   lscs			- Local system permanent information
 *   scs_cbvtdb			- CB vector table database pointer
 *
 *   Outputs:
 *
 *   IPL_SCS			- Interrupt processor level
 *   cb				- Connection Block pointer
 *	cinfo.cbstate		-  CB state
 *	cinfo.pend_rec_credit	-  0
 *	cinfo.msgs_sent		-  Number of sequenced messages sent
 *	cinfo.rec_credit	-  Send credit held by remote SYSAP
 *	cinfo.snd_credit	-  Number of send credits
 *	cinfo.status.cwait	-  SYSAP waiting for send credits flag
 *   csb			- Communication Services Block pointer
 *	buf			-  NULL
 *
 *   Return Values:
 *
 *   RET_SUCCESS		- Successfully initiated message transmission
 *   RET_INVCONNID		- Invalid connection identification number
 *   RET_INVCSTATE		- Connection in invalid state
 *   RET_NOCREDITS		- No send credits available
 *
 *   SMP:	The CB is locked to synchronize access and prevent deletion.
 *		It is indirectly locked through its CBVTE.  Locking the CB also
 *		prevents PB deletion as required by PD routines which transmit
 *		messages.
 *
 *		The PB is specifically locked when it is found necessary to
 *		remove the CB from the PB's work queue.
 */
u_long
scs_send_msg( csb )
    register CSB	*csb;
{
    register CB		*cb;
    register SCSH	*scsbp;
    register CBVTE	*cbvte;
    register u_long	dispose, status = RET_SUCCESS;

    /* Transmissions of application sequenced messages proceed as follows:
     *
     * 1. Lock and retrieve the CB.
     * 2. Allocate a send credit.
     * 3. Abort any explicit SCS send credit extensions in progress( Any send
     *    credits to be extended go out within the outgoing sequenced message
     *    itself ).
     * 4. Initialize the SCS header of the application message buffer.
     * 5. Perform connection bookkeeping.
     * 6. Invoke a PD specific routine to initiate application sequenced
     *	  message transmission
     * 7. Unlock the CB.
     * 8. Return an appropriate status.
     *
     * Lack of send credits on the connection is remembered.  The SYSAP is
     * notified when send credits are again available.
     *
     * The message buffer is converted into a receive message buffer instead of
     * deallocated whenever the current number of receive buffers is less than
     * the maximum number.  Furthermore, the number of send credits pending
     * extension is incremented whenever the message buffer is to be converted
     * into a receive message buffer following its transmission.  This has the
     * effect of extending the send credit for the new receive buffer within
     * the outgoing sequenced message.
     */
    Check_connid( csb->connid, cbvte, cb )
    if( cb->cinfo.cstate != CS_OPEN ) {
	status = RET_INVCSTATE;
    } else if(( long )--cb->cinfo.snd_credit >= 0 ) {
	if(( dispose = csb->Disposal ) == RECEIVE_BUF ) {
	    ++cb->cinfo.pend_rec_credit;
	} else if(( cb->cinfo.rec_credit +
		  cb->cinfo.pend_rec_credit ) < cb->cinfo.init_rec_credit ) {
	    ++cb->cinfo.pend_rec_credit;
	    dispose = RECEIVE_BUF;
	}
	Remove_pb_waitq( cb )
	scsbp = Appl_to_scs( csb->buf );
	csb->buf = NULL;
	U_long( scsbp->mtype ) = SCS_APPL_MSG;
	if(( scsbp->credit = cb->cinfo.pend_rec_credit )) {
	    cb->cinfo.rec_credit += cb->cinfo.pend_rec_credit;
	    cb->cinfo.pend_rec_credit = 0;
	}
	Move_connid( cb->cinfo.rconnid, scsbp->rconnid )
	Move_connid( cb->cinfo.lconnid, scsbp->sconnid )
	Event_counter( cb->cinfo.msgs_snt )
	( void )( *cb->Send_msg )( cb->pccb,
				   cb->pb,
				   scsbp,
				   ( csb->size + sizeof( SCSH )),
				   dispose );
    } else {
	cb->cinfo.snd_credit = 0;
	cb->cinfo.status.cwait = 1;
	status = RET_NOCREDITS;
    }
    Unlock_cbvte( cbvte );
    return( status );
}