gru: fix handling of mesq failures

Fix endcase in handling GRU message queue failures due to NACKs of PUT
requests.  Must ensure that the "present" bits are cleared before
resending the message.
Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/misc/sgi-gru/grukservices.c

@@ -503,6 +503,29 @@ static void send_message_queue_interrupt(struct gru_message_queue_desc *mqd)
 				mqd->interrupt_vector);
 }
 
+/*
+ * Handle a PUT failure. Note: if message was a 2-line message, one of the
+ * lines might have successfully have been written. Before sending the
+ * message, "present" must be cleared in BOTH lines to prevent the receiver
+ * from prematurely seeing the full message.
+ */
+static int send_message_put_nacked(void *cb, struct gru_message_queue_desc *mqd,
+			void *mesg, int lines)
+{
+	unsigned long m;
+
+	m = mqd->mq_gpa + (gru_get_amo_value_head(cb) << 6);
+	if (lines == 2) {
+		gru_vset(cb, m, 0, XTYPE_CL, lines, 1, IMA);
+		if (gru_wait(cb) != CBS_IDLE)
+			return MQE_UNEXPECTED_CB_ERR;
+	}
+	gru_vstore(cb, m, gru_get_tri(mesg), XTYPE_CL, lines, 1, IMA);
+	if (gru_wait(cb) != CBS_IDLE)
+		return MQE_UNEXPECTED_CB_ERR;
+	send_message_queue_interrupt(mqd);
+	return MQE_OK;
+}
 
 /*
  * Handle a gru_mesq failure. Some of these failures are software recoverable
@@ -512,7 +535,6 @@ static int send_message_failure(void *cb, struct gru_message_queue_desc *mqd,
 				void *mesg, int lines)
 {
 	int substatus, ret = 0;
-	unsigned long m;
 
 	substatus = gru_get_cb_message_queue_substatus(cb);
 	switch (substatus) {
@@ -534,14 +556,7 @@ static int send_message_failure(void *cb, struct gru_message_queue_desc *mqd,
 		break;
 	case CBSS_PUT_NACKED:
 		STAT(mesq_send_put_nacked);
-		m = mqd->mq_gpa + (gru_get_amo_value_head(cb) << 6);
-		gru_vstore(cb, m, gru_get_tri(mesg), XTYPE_CL, lines, 1, IMA);
-		if (gru_wait(cb) == CBS_IDLE) {
-			ret = MQE_OK;
-			send_message_queue_interrupt(mqd);
-		} else {
-			ret = MQE_UNEXPECTED_CB_ERR;
-		}
+		ret = send_message_put_nacked(cb, mqd, mesg, lines);
 		break;
 	default:
 		BUG();