diff mbox

[v2,net-next,6/9] sunvnet: straighten up message event handling logic

Message ID 1486505582-76823-7-git-send-email-shannon.nelson@oracle.com
State Changes Requested, archived
Delegated to: David Miller
Headers show

Commit Message

Shannon Nelson Feb. 7, 2017, 10:12 p.m. UTC 
The use of gotos for handling the incoming events made this code
harder to read and support than it should be.  This patch straightens
out and clears up the logic.

Signed-off-by: Shannon Nelson <shannon.nelson@oracle.com>
---
 drivers/net/ethernet/sun/sunvnet_common.c |   94 ++++++++++++++---------------
 1 files changed, 45 insertions(+), 49 deletions(-)

Comments

Sowmini Varadhan Feb. 8, 2017, 3:59 p.m. UTC | #1 
On (02/07/17 14:12), Shannon Nelson wrote:
> +
> +	/* we don't expect any other bits */
> +	BUG_ON(port->rx_event & ~(LDC_EVENT_DATA_READY |
> +				  LDC_EVENT_RESET |
> +				  LDC_EVENT_UP));
> +
> +	/* RESET takes precedent over any other event */
> +	if (port->rx_event & LDC_EVENT_RESET) { 
                  :
>  		port->rx_event = 0;
>  		return 0;
>  	}
> +	if (port->rx_event & LDC_EVENT_UP) {
> +		vio_link_state_change(vio, LDC_EVENT_UP);
> +		port->rx_event = 0;
> +		return 0;
> +	}
>  
>  	err = 0;
>  	tx_wakeup = 0;

IIRC there were timing-related situations where you can get woken up with
both UP and DATA_READY, and if my reading of your patch is 
correct, we would ignore the DATA_READY, and return, right?

--Sowmini
Shannon Nelson Feb. 8, 2017, 4:28 p.m. UTC | #2 
On 2/8/2017 7:59 AM, Sowmini Varadhan wrote:
> On (02/07/17 14:12), Shannon Nelson wrote:
>> +
>> +	/* we don't expect any other bits */
>> +	BUG_ON(port->rx_event & ~(LDC_EVENT_DATA_READY |
>> +				  LDC_EVENT_RESET |
>> +				  LDC_EVENT_UP));
>> +
>> +	/* RESET takes precedent over any other event */
>> +	if (port->rx_event & LDC_EVENT_RESET) {
>                   :
>>  		port->rx_event = 0;
>>  		return 0;
>>  	}
>> +	if (port->rx_event & LDC_EVENT_UP) {
>> +		vio_link_state_change(vio, LDC_EVENT_UP);
>> +		port->rx_event = 0;
>> +		return 0;
>> +	}
>>
>>  	err = 0;
>>  	tx_wakeup = 0;
>
> IIRC there were timing-related situations where you can get woken up with
> both UP and DATA_READY, and if my reading of your patch is
> correct, we would ignore the DATA_READY, and return, right?
>
> --Sowmini

The existing code does this as well - if it first finds a RESET, it 
handles it then hits the return 0.  Next if it finds the UP, it does the 
goto back to the ldc_ctrl: to process, and hits the same return 0.  Only 
if neither of these bits have been seen does the code move on to process 
the DATA_READY event.

If we're seeing cases of both UP and DATA_READY, then yes we'll wnat to 
look at changing this logic.  I think that should be a separate patch.

sln
Sowmini Varadhan Feb. 8, 2017, 4:34 p.m. UTC | #3 
On (02/08/17 08:28), Shannon Nelson wrote:
> The existing code does this as well - if it first finds a RESET, it handles
> it then hits the return 0.  Next if it finds the UP, it does the goto back
> to the ldc_ctrl: to process, and hits the same return 0.  Only if neither of
> these bits have been seen does the code move on to process the DATA_READY
> event.
> 
> If we're seeing cases of both UP and DATA_READY, then yes we'll wnat to look
> at changing this logic.  I think that should be a separate patch.
> 

Ok. probably we just make one redundant loop out and back into the function.

Other than that, the patchset looks good to me.

--Sowmini
diff mbox

Patch

diff --git a/drivers/net/ethernet/sun/sunvnet_common.c b/drivers/net/ethernet/sun/sunvnet_common.c
index 6cb625a..d2aed2c 100644
--- a/drivers/net/ethernet/sun/sunvnet_common.c
+++ b/drivers/net/ethernet/sun/sunvnet_common.c
@@ -764,41 +764,37 @@  static int vnet_event_napi(struct vnet_port *port, int budget)
 	struct vio_driver_state *vio = &port->vio;
 	int tx_wakeup, err;
 	int npkts = 0;
-	int event = (port->rx_event & LDC_EVENT_RESET);
-
-ldc_ctrl:
-	if (unlikely(event == LDC_EVENT_RESET ||
-		     event == LDC_EVENT_UP)) {
-		vio_link_state_change(vio, event);
-
-		if (event == LDC_EVENT_RESET) {
-			vnet_port_reset(port);
-			vio_port_up(vio);
-
-			/* If the device is running but its tx queue was
-			 * stopped (due to flow control), restart it.
-			 * This is necessary since vnet_port_reset()
-			 * clears the tx drings and thus we may never get
-			 * back a VIO_TYPE_DATA ACK packet - which is
-			 * the normal mechanism to restart the tx queue.
-			 */
-			if (netif_running(dev))
-				maybe_tx_wakeup(port);
-		}
+
+	/* we don't expect any other bits */
+	BUG_ON(port->rx_event & ~(LDC_EVENT_DATA_READY |
+				  LDC_EVENT_RESET |
+				  LDC_EVENT_UP));
+
+	/* RESET takes precedent over any other event */
+	if (port->rx_event & LDC_EVENT_RESET) {
+		vio_link_state_change(vio, LDC_EVENT_RESET);
+		vnet_port_reset(port);
+		vio_port_up(vio);
+
+		/* If the device is running but its tx queue was
+		 * stopped (due to flow control), restart it.
+		 * This is necessary since vnet_port_reset()
+		 * clears the tx drings and thus we may never get
+		 * back a VIO_TYPE_DATA ACK packet - which is
+		 * the normal mechanism to restart the tx queue.
+		 */
+		if (netif_running(dev))
+			maybe_tx_wakeup(port);
+
 		port->rx_event = 0;
 		return 0;
 	}
-	/* We may have multiple LDC events in rx_event. Unroll send_events() */
-	event = (port->rx_event & LDC_EVENT_UP);
-	port->rx_event &= ~(LDC_EVENT_RESET | LDC_EVENT_UP);
-	if (event == LDC_EVENT_UP)
-		goto ldc_ctrl;
-	event = port->rx_event;
-	if (!(event & LDC_EVENT_DATA_READY))
-		return 0;
 
-	/* we dont expect any other bits than RESET, UP, DATA_READY */
-	BUG_ON(event != LDC_EVENT_DATA_READY);
+	if (port->rx_event & LDC_EVENT_UP) {
+		vio_link_state_change(vio, LDC_EVENT_UP);
+		port->rx_event = 0;
+		return 0;
+	}
 
 	err = 0;
 	tx_wakeup = 0;
@@ -821,25 +817,25 @@  static int vnet_event_napi(struct vnet_port *port, int budget)
 			pkt->start_idx = vio_dring_next(dr,
 							port->napi_stop_idx);
 			pkt->end_idx = -1;
-			goto napi_resume;
-		}
-		err = ldc_read(vio->lp, &msgbuf, sizeof(msgbuf));
-		if (unlikely(err < 0)) {
-			if (err == -ECONNRESET)
-				vio_conn_reset(vio);
-			break;
+		} else {
+			err = ldc_read(vio->lp, &msgbuf, sizeof(msgbuf));
+			if (unlikely(err < 0)) {
+				if (err == -ECONNRESET)
+					vio_conn_reset(vio);
+				break;
+			}
+			if (err == 0)
+				break;
+			viodbg(DATA, "TAG [%02x:%02x:%04x:%08x]\n",
+			       msgbuf.tag.type,
+			       msgbuf.tag.stype,
+			       msgbuf.tag.stype_env,
+			       msgbuf.tag.sid);
+			err = vio_validate_sid(vio, &msgbuf.tag);
+			if (err < 0)
+				break;
 		}
-		if (err == 0)
-			break;
-		viodbg(DATA, "TAG [%02x:%02x:%04x:%08x]\n",
-		       msgbuf.tag.type,
-		       msgbuf.tag.stype,
-		       msgbuf.tag.stype_env,
-		       msgbuf.tag.sid);
-		err = vio_validate_sid(vio, &msgbuf.tag);
-		if (err < 0)
-			break;
-napi_resume:
+
 		if (likely(msgbuf.tag.type == VIO_TYPE_DATA)) {
 			if (msgbuf.tag.stype == VIO_SUBTYPE_INFO) {
 				if (!sunvnet_port_is_up_common(port)) {