[S390] qdio: fix error reporting for hipersockets

Hipersocket connections can encounter temporary busy conditions.
In case of the busy bit set we retry the SIGA operation immediatelly.
If the busy condition still persists after 100 ms we fail and report
the error to the upper layer. The second stage retry logic is removed.
In case of ongoing busy conditions the upper layer needs to reset the
connection.

The reporting of a SIGA error is now done synchronously to allow the
network driver to requeue the buffers. Also no error trace is created
for the temporary SIGA errors so the error message view is not flooded.
Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/qdio.h

@@ -14,7 +14,6 @@
 #include "chsc.h"
 
 #define QDIO_BUSY_BIT_PATIENCE		100	/* 100 microseconds */
-#define QDIO_BUSY_BIT_GIVE_UP		2000000	/* 2 seconds = eternity */
 #define QDIO_INPUT_THRESHOLD		500	/* 500 microseconds */
 
 /*
@@ -195,12 +194,6 @@ struct qdio_input_q {
 };
 
 struct qdio_output_q {
-	/* failed siga-w attempts*/
-	atomic_t busy_siga_counter;
-
-	/* start time of busy condition */
-	u64 timestamp;
-
 	/* PCIs are enabled for the queue */
 	int pci_out_enabled;
 
@@ -251,6 +244,7 @@ struct qdio_q {
 
 	struct qdio_irq *irq_ptr;
 	struct tasklet_struct tasklet;
+	spinlock_t lock;
 
 	/* error condition during a data transfer */
 	unsigned int qdio_error;

drivers/s390/cio/qdio_main.c

@@ -74,7 +74,7 @@ static inline int do_siga_input(struct subchannel_id schid, unsigned int mask)
  * Note: For IQDC unicast queues only the highest priority queue is processed.
  */
 static inline int do_siga_output(unsigned long schid, unsigned long mask,
-				 u32 *bb, unsigned int fc)
+				 unsigned int *bb, unsigned int fc)
 {
 	register unsigned long __fc asm("0") = fc;
 	register unsigned long __schid asm("1") = schid;
@@ -284,8 +284,7 @@ static int qdio_siga_sync(struct qdio_q *q, unsigned int output,
 	if (!need_siga_sync(q))
 		return 0;
 
-	DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "siga-s:");
-	DBF_DEV_HEX(DBF_INFO, q->irq_ptr, q, sizeof(void *));
+	DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "siga-s:%1d", q->nr);
 	qdio_perf_stat_inc(&perf_stats.siga_sync);
 
 	cc = do_siga_sync(q->irq_ptr->schid, output, input);
@@ -312,46 +311,37 @@ static inline int qdio_siga_sync_all(struct qdio_q *q)
 	return qdio_siga_sync(q, ~0U, ~0U);
 }
 
-static inline int qdio_do_siga_output(struct qdio_q *q, unsigned int *busy_bit)
+static int qdio_siga_output(struct qdio_q *q, unsigned int *busy_bit)
 {
-	unsigned int fc = 0;
 	unsigned long schid;
+	unsigned int fc = 0;
+	u64 start_time = 0;
+	int cc;
 
-	if (q->u.out.use_enh_siga) {
+	if (q->u.out.use_enh_siga)
 		fc = 3;
-	}
-	if (!is_qebsm(q))
-		schid = *((u32 *)&q->irq_ptr->schid);
-	else {
+
+	if (is_qebsm(q)) {
 		schid = q->irq_ptr->sch_token;
 		fc |= 0x80;
 	}
-	return do_siga_output(schid, q->mask, busy_bit, fc);
-}
-
-static int qdio_siga_output(struct qdio_q *q)
-{
-	int cc;
-	u32 busy_bit;
-	u64 start_time = 0;
+	else
+		schid = *((u32 *)&q->irq_ptr->schid);
 
-	DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "siga-w:%1d", q->nr);
-	qdio_perf_stat_inc(&perf_stats.siga_out);
 again:
-	cc = qdio_do_siga_output(q, &busy_bit);
-	if (queue_type(q) == QDIO_IQDIO_QFMT && cc == 2 && busy_bit) {
-		DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "siga-w bb:%2d", q->nr);
+	cc = do_siga_output(schid, q->mask, busy_bit, fc);
+
+	/* hipersocket busy condition */
+	if (*busy_bit) {
+		WARN_ON(queue_type(q) != QDIO_IQDIO_QFMT || cc != 2);
 
-		if (!start_time)
+		if (!start_time) {
 			start_time = get_usecs();
-		else if ((get_usecs() - start_time) < QDIO_BUSY_BIT_PATIENCE)
+			goto again;
+		}
+		if ((get_usecs() - start_time) < QDIO_BUSY_BIT_PATIENCE)
 			goto again;
 	}
-
-	if (cc == 2 && busy_bit)
-		cc |= QDIO_ERROR_SIGA_BUSY;
-	if (cc)
-		DBF_ERROR("%4x SIGA-W:%2d", SCH_NO(q), cc);
 	return cc;
 }
 
@@ -399,7 +389,7 @@ inline void qdio_stop_polling(struct qdio_q *q)
 
 static void announce_buffer_error(struct qdio_q *q, int count)
 {
-	q->qdio_error = QDIO_ERROR_SLSB_STATE;
+	q->qdio_error |= QDIO_ERROR_SLSB_STATE;
 
 	/* special handling for no target buffer empty */
 	if ((!q->is_input_q &&
@@ -716,68 +706,36 @@ static inline int qdio_outbound_q_moved(struct qdio_q *q)
 		return 0;
 }
 
-/*
- * VM could present us cc=2 and busy bit set on SIGA-write
- * during reconfiguration of their Guest LAN (only in iqdio mode,
- * otherwise qdio is asynchronous and cc=2 and busy bit there will take
- * the queues down immediately).
- *
- * Therefore qdio_siga_output will try for a short time constantly,
- * if such a condition occurs. If it doesn't change, it will
- * increase the busy_siga_counter and save the timestamp, and
- * schedule the queue for later processing. qdio_outbound_processing
- * will check out the counter. If non-zero, it will call qdio_kick_outbound_q
- * as often as the value of the counter. This will attempt further SIGA
- * instructions. For each successful SIGA, the counter is
- * decreased, for failing SIGAs the counter remains the same, after
- * all. After some time of no movement, qdio_kick_outbound_q will
- * finally fail and reflect corresponding error codes to call
- * the upper layer module and have it take the queues down.
- *
- * Note that this is a change from the original HiperSockets design
- * (saying cc=2 and busy bit means take the queues down), but in
- * these days Guest LAN didn't exist... excessive cc=2 with busy bit
- * conditions will still take the queues down, but the threshold is
- * higher due to the Guest LAN environment.
- *
- * Called from outbound tasklet and do_QDIO handler.
- */
 static void qdio_kick_outbound_q(struct qdio_q *q)
 {
-	int rc;
-
-	DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "kickoutq:%1d", q->nr);
+	unsigned int busy_bit;
+	int cc;
 
 	if (!need_siga_out(q))
 		return;
 
-	rc = qdio_siga_output(q);
-	switch (rc) {
+	DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "siga-w:%1d", q->nr);
+	qdio_perf_stat_inc(&perf_stats.siga_out);
+
+	cc = qdio_siga_output(q, &busy_bit);
+	switch (cc) {
 	case 0:
-		/* TODO: improve error handling for CC=0 case */
-		if (q->u.out.timestamp)
-			DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "cc2 rslv:%4x",
-				      atomic_read(&q->u.out.busy_siga_counter));
-		/* went smooth this time, reset timestamp */
-		q->u.out.timestamp = 0;
 		break;
-	/* cc=2 and busy bit */
-	case (2 | QDIO_ERROR_SIGA_BUSY):
-		atomic_inc(&q->u.out.busy_siga_counter);
-
-		/* if the last siga was successful, save timestamp here */
-		if (!q->u.out.timestamp)
-			q->u.out.timestamp = get_usecs();
-
-		/* if we're in time, don't touch qdio_error */
-		if (get_usecs() - q->u.out.timestamp < QDIO_BUSY_BIT_GIVE_UP) {
-			tasklet_schedule(&q->tasklet);
-			break;
+	case 2:
+		if (busy_bit) {
+			DBF_ERROR("%4x cc2 REP:%1d", SCH_NO(q), q->nr);
+			q->qdio_error = cc | QDIO_ERROR_SIGA_BUSY;
+		} else {
+			DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "siga-w cc2:%1d",
+				      q->nr);
+			q->qdio_error = cc;
 		}
-		DBF_ERROR("%4x cc2 REP:%1d", SCH_NO(q), q->nr);
-	default:
-		/* for plain cc=1, 2 or 3 */
-		q->qdio_error = rc;
+		break;
+	case 1:
+	case 3:
+		DBF_ERROR("%4x SIGA-W:%1d", SCH_NO(q), cc);
+		q->qdio_error = cc;
+		break;
 	}
 }
 
@@ -808,22 +766,18 @@ static void qdio_kick_outbound_handler(struct qdio_q *q)
 
 static void __qdio_outbound_processing(struct qdio_q *q)
 {
-	int siga_attempts;
+	unsigned long flags;
 
 	qdio_perf_stat_inc(&perf_stats.tasklet_outbound);
-
-	/* see comment in qdio_kick_outbound_q */
-	siga_attempts = atomic_read(&q->u.out.busy_siga_counter);
-	while (siga_attempts--) {
-		atomic_dec(&q->u.out.busy_siga_counter);
-		qdio_kick_outbound_q(q);
-	}
+	spin_lock_irqsave(&q->lock, flags);
 
 	BUG_ON(atomic_read(&q->nr_buf_used) < 0);
 
 	if (qdio_outbound_q_moved(q))
 		qdio_kick_outbound_handler(q);
 
+	spin_unlock_irqrestore(&q->lock, flags);
+
 	if (queue_type(q) == QDIO_ZFCP_QFMT) {
 		if (!pci_out_supported(q) && !qdio_outbound_q_done(q))
 			tasklet_schedule(&q->tasklet);
@@ -1491,7 +1445,7 @@ static inline int buf_in_between(int bufnr, int start, int count)
 static void handle_inbound(struct qdio_q *q, unsigned int callflags,
 			   int bufnr, int count)
 {
-	int used, rc, diff;
+	int used, cc, diff;
 
 	if (!q->u.in.polling)
 		goto set;
@@ -1532,9 +1486,9 @@ static void handle_inbound(struct qdio_q *q, unsigned int callflags,
 		return;
 
 	if (need_siga_in(q)) {
-		rc = qdio_siga_input(q);
-		if (rc)
-			q->qdio_error = rc;
+		cc = qdio_siga_input(q);
+		if (cc)
+			q->qdio_error = cc;
 	}
 }
 
@@ -1581,6 +1535,10 @@ static void handle_outbound(struct qdio_q *q, unsigned int callflags,
 				while (count--)
 					qdio_kick_outbound_q(q);
 			}
+
+		/* report CC=2 conditions synchronously */
+		if (q->qdio_error)
+			__qdio_outbound_processing(q);
 		goto out;
 	}
 

drivers/s390/cio/qdio_setup.c

@@ -117,6 +117,7 @@ static void setup_queues_misc(struct qdio_q *q, struct qdio_irq *irq_ptr,
 	q->mask = 1 << (31 - i);
 	q->nr = i;
 	q->handler = handler;
+	spin_lock_init(&q->lock);
 }
 
 static void setup_storage_lists(struct qdio_q *q, struct qdio_irq *irq_ptr,