x86, UV2: BAU fixes for UV version 2

Index: 120113.linux-3.2.1/arch/x86/include/asm/uv/uv_bau.h
===================================================================
@@ -65,7 +65,7 @@
  * UV2: Bit 19 selects between
  *  (0): 10 microsecond timebase and
  *  (1): 80 microseconds
- *  we're using 655us, similar to UV1: 65 units of 10us
+ *  we're using 560us, similar to UV1: 65 units of 10us
  */
 #define UV1_INTD_SOFT_ACK_TIMEOUT_PERIOD (9UL)
 #define UV2_INTD_SOFT_ACK_TIMEOUT_PERIOD (15UL)

@@ -235,10 +235,10 @@ struct bau_msg_payload {
 
 
 /*
- * Message header:  16 bytes (128 bits) (bytes 0x30-0x3f of descriptor)
+ * UV1 Message header:  16 bytes (128 bits) (bytes 0x30-0x3f of descriptor)
  * see table 4.2.3.0.1 in broacast_assist spec.
  */
-struct bau_msg_header {
+struct uv1_bau_msg_header {
 	unsigned int	dest_subnodeid:6;	/* must be 0x10, for the LB */
 	/* bits 5:0 */
 	unsigned int	base_dest_nasid:15;	/* nasid of the first bit */

@@ -318,19 +318,87 @@ struct bau_msg_header {
 };
 
 /*
+ * UV2 Message header:  16 bytes (128 bits) (bytes 0x30-0x3f of descriptor)
+ * see figure 9-2 of harp_sys.pdf
+ */
+struct uv2_bau_msg_header {
+	unsigned int	base_dest_nasid:15;	/* nasid of the first bit */
+	/* bits 14:0 */				/* in uvhub map */
+	unsigned int	dest_subnodeid:5;	/* must be 0x10, for the LB */
+	/* bits 19:15 */
+	unsigned int	rsvd_1:1;		/* must be zero */
+	/* bit 20 */
+	/* Address bits 59:21 */
+	/* bits 25:2 of address (44:21) are payload */
+	/* these next 24 bits become bytes 12-14 of msg */
+	/* bits 28:21 land in byte 12 */
+	unsigned int	replied_to:1;		/* sent as 0 by the source to
+						   byte 12 */
+	/* bit 21 */
+	unsigned int	msg_type:3;		/* software type of the
+						   message */
+	/* bits 24:22 */
+	unsigned int	canceled:1;		/* message canceled, resource
+						   is to be freed*/
+	/* bit 25 */
+	unsigned int	payload_1:3;		/* not currently used */
+	/* bits 28:26 */
+
+	/* bits 36:29 land in byte 13 */
+	unsigned int	payload_2a:3;		/* not currently used */
+	unsigned int	payload_2b:5;		/* not currently used */
+	/* bits 36:29 */
+
+	/* bits 44:37 land in byte 14 */
+	unsigned int	payload_3:8;		/* not currently used */
+	/* bits 44:37 */
+
+	unsigned int	rsvd_2:7;		/* reserved */
+	/* bits 51:45 */
+	unsigned int	swack_flag:1;		/* software acknowledge flag */
+	/* bit 52 */
+	unsigned int	rsvd_3a:3;		/* must be zero */
+	unsigned int	rsvd_3b:8;		/* must be zero */
+	unsigned int	rsvd_3c:8;		/* must be zero */
+	unsigned int	rsvd_3d:3;		/* must be zero */
+	/* bits 74:53 */
+	unsigned int	fairness:3;		/* usually zero */
+	/* bits 77:75 */
+
+	unsigned int	sequence:16;		/* message sequence number */
+	/* bits 93:78  Suppl_A  */
+	unsigned int	chaining:1;		/* next descriptor is part of
+						   this activation*/
+	/* bit 94 */
+	unsigned int	multilevel:1;		/* multi-level multicast
+						   format */
+	/* bit 95 */
+	unsigned int	rsvd_4:24;		/* ordered / source node /
+						   source subnode / aging
+						   must be zero */
+	/* bits 119:96 */
+	unsigned int	command:8;		/* message type */
+	/* bits 127:120 */
+};
+
+/*
  * The activation descriptor:
  * The format of the message to send, plus all accompanying control
  * Should be 64 bytes
  */
 struct bau_desc {
-	struct pnmask			distribution;
+	struct pnmask				distribution;
 	/*
 	 * message template, consisting of header and payload:
 	 */
-	struct bau_msg_header		header;
-	struct bau_msg_payload		payload;
+	union bau_msg_header {
+		struct uv1_bau_msg_header	uv1_hdr;
+		struct uv2_bau_msg_header	uv2_hdr;
+	} header;
+
+	struct bau_msg_payload			payload;
 };
-/*
+/* UV1:
  *   -payload--    ---------header------
  *   bytes 0-11    bits 41-56  bits 58-81
  *       A           B  (2)      C (3)

@@ -340,6 +408,16 @@ struct bau_desc {
  *   bytes 0-11  bytes 12-14  bytes 16-17  (byte 15 filled in by hw as vector)
  *   ------------payload queue-----------
  */
+/* UV2:
+ *   -payload--    ---------header------
+ *   bytes 0-11    bits 70-78  bits 21-44
+ *       A           B  (2)      C (3)
+ *
+ *            A/B/C are moved to:
+ *       A            C          B
+ *   bytes 0-11  bytes 12-14  bytes 16-17  (byte 15 filled in by hw as vector)
+ *   ------------payload queue-----------
+ */
 
 /*
  * The payload queue on the destination side is an array of these.

@@ -511,6 +589,7 @@ struct bau_control {
 	short			osnode;
 	short			uvhub_cpu;
 	short			uvhub;
+	short			uvhub_version;
 	short			cpus_in_socket;
 	short			cpus_in_uvhub;
 	short			partition_base_pnode;

167 lines not on this page · raw message

index 8e862aa..4a46b27 100644
@@ -65,7 +65,7 @@
  * UV2: Bit 19 selects between
  *  (0): 10 microsecond timebase and
  *  (1): 80 microseconds
- *  we're using 655us, similar to UV1: 65 units of 10us
+ *  we're using 560us, similar to UV1: 65 units of 10us
  */
 #define UV1_INTD_SOFT_ACK_TIMEOUT_PERIOD (9UL)
 #define UV2_INTD_SOFT_ACK_TIMEOUT_PERIOD (15UL)

@@ -235,10 +235,10 @@ struct bau_msg_payload {
 
 
 /*
- * Message header:  16 bytes (128 bits) (bytes 0x30-0x3f of descriptor)
+ * UV1 Message header:  16 bytes (128 bits) (bytes 0x30-0x3f of descriptor)
  * see table 4.2.3.0.1 in broacast_assist spec.
  */
-struct bau_msg_header {
+struct uv1_bau_msg_header {
 	unsigned int	dest_subnodeid:6;	/* must be 0x10, for the LB */
 	/* bits 5:0 */
 	unsigned int	base_dest_nasid:15;	/* nasid of the first bit */

@@ -318,19 +318,87 @@ struct bau_msg_header {
 };
 
 /*
+ * UV2 Message header:  16 bytes (128 bits) (bytes 0x30-0x3f of descriptor)
+ * see figure 9-2 of harp_sys.pdf
+ */
+struct uv2_bau_msg_header {
+	unsigned int	base_dest_nasid:15;	/* nasid of the first bit */
+	/* bits 14:0 */				/* in uvhub map */
+	unsigned int	dest_subnodeid:5;	/* must be 0x10, for the LB */
+	/* bits 19:15 */
+	unsigned int	rsvd_1:1;		/* must be zero */
+	/* bit 20 */
+	/* Address bits 59:21 */
+	/* bits 25:2 of address (44:21) are payload */
+	/* these next 24 bits become bytes 12-14 of msg */
+	/* bits 28:21 land in byte 12 */
+	unsigned int	replied_to:1;		/* sent as 0 by the source to
+						   byte 12 */
+	/* bit 21 */
+	unsigned int	msg_type:3;		/* software type of the
+						   message */
+	/* bits 24:22 */
+	unsigned int	canceled:1;		/* message canceled, resource
+						   is to be freed*/
+	/* bit 25 */
+	unsigned int	payload_1:3;		/* not currently used */
+	/* bits 28:26 */
+
+	/* bits 36:29 land in byte 13 */
+	unsigned int	payload_2a:3;		/* not currently used */
+	unsigned int	payload_2b:5;		/* not currently used */
+	/* bits 36:29 */
+
+	/* bits 44:37 land in byte 14 */
+	unsigned int	payload_3:8;		/* not currently used */
+	/* bits 44:37 */
+
+	unsigned int	rsvd_2:7;		/* reserved */
+	/* bits 51:45 */
+	unsigned int	swack_flag:1;		/* software acknowledge flag */
+	/* bit 52 */
+	unsigned int	rsvd_3a:3;		/* must be zero */
+	unsigned int	rsvd_3b:8;		/* must be zero */
+	unsigned int	rsvd_3c:8;		/* must be zero */
+	unsigned int	rsvd_3d:3;		/* must be zero */
+	/* bits 74:53 */
+	unsigned int	fairness:3;		/* usually zero */
+	/* bits 77:75 */
+
+	unsigned int	sequence:16;		/* message sequence number */
+	/* bits 93:78  Suppl_A  */
+	unsigned int	chaining:1;		/* next descriptor is part of
+						   this activation*/
+	/* bit 94 */
+	unsigned int	multilevel:1;		/* multi-level multicast
+						   format */
+	/* bit 95 */
+	unsigned int	rsvd_4:24;		/* ordered / source node /
+						   source subnode / aging
+						   must be zero */
+	/* bits 119:96 */
+	unsigned int	command:8;		/* message type */
+	/* bits 127:120 */
+};
+
+/*
  * The activation descriptor:
  * The format of the message to send, plus all accompanying control
  * Should be 64 bytes
  */
 struct bau_desc {
-	struct pnmask			distribution;
+	struct pnmask				distribution;
 	/*
 	 * message template, consisting of header and payload:
 	 */
-	struct bau_msg_header		header;
-	struct bau_msg_payload		payload;
+	union bau_msg_header {
+		struct uv1_bau_msg_header	uv1_hdr;
+		struct uv2_bau_msg_header	uv2_hdr;
+	} header;
+
+	struct bau_msg_payload			payload;
 };
-/*
+/* UV1:
  *   -payload--    ---------header------
  *   bytes 0-11    bits 41-56  bits 58-81
  *       A           B  (2)      C (3)

@@ -340,6 +408,16 @@ struct bau_desc {
  *   bytes 0-11  bytes 12-14  bytes 16-17  (byte 15 filled in by hw as vector)
  *   ------------payload queue-----------
  */
+/* UV2:
+ *   -payload--    ---------header------
+ *   bytes 0-11    bits 70-78  bits 21-44
+ *       A           B  (2)      C (3)
+ *
+ *            A/B/C are moved to:
+ *       A            C          B
+ *   bytes 0-11  bytes 12-14  bytes 16-17  (byte 15 filled in by hw as vector)
+ *   ------------payload queue-----------
+ */
 
 /*
  * The payload queue on the destination side is an array of these.

@@ -511,6 +589,7 @@ struct bau_control {
 	short			osnode;
 	short			uvhub_cpu;
 	short			uvhub;
+	short			uvhub_version;
 	short			cpus_in_socket;
 	short			cpus_in_uvhub;
 	short			partition_base_pnode;

167 lines not on this page · raw message

Index: 120113.linux-3.2.1/arch/x86/platform/uv/tlb_uv.c
===================================================================
@@ -1617,14 +1617,14 @@ static int calculate_destination_timeout
 		ts_ns = base * mult1 * mult2;
 		ret = ts_ns / 1000;
 	} else {
-		/* 4 bits  0/1 for 10/80us, 3 bits of multiplier */
-		mmr_image = uv_read_local_mmr(UVH_AGING_PRESCALE_SEL);
+		/* 4 bits  0/1 for 10/80us base, 3 bits of multiplier */
+		mmr_image = uv_read_local_mmr(UVH_LB_BAU_MISC_CONTROL);
 		mmr_image = (mmr_image & UV_SA_MASK) >> UV_SA_SHFT;
 		if (mmr_image & (1L << UV2_ACK_UNITS_SHFT))
-			mult1 = 80;
+			base = 80;
 		else
-			mult1 = 10;
-		base = mmr_image & UV2_ACK_MASK;
+			base = 10;
+		mult1 = mmr_image & UV2_ACK_MASK;
 		ret = mult1 * base;
 	}
 	return ret;

@@ -1886,6 +1886,8 @@ static int __init uv_bau_init(void)
 			uv_base_pnode = uv_blade_to_pnode(uvhub);
 	}
 
+	enable_timeouts();
+
 	if (init_per_cpu(nuvhubs, uv_base_pnode)) {
 		nobau = 1;
 		return 0;

@@ -1896,7 +1898,6 @@ static int __init uv_bau_init(void)
 		if (uv_blade_nr_possible_cpus(uvhub))
 			init_uvhub(uvhub, vector, uv_base_pnode);
 
-	enable_timeouts();
 	alloc_intr_gate(vector, uv_bau_message_intr1);
 
 	for_each_possible_blade(uvhub) {

index 1341a2e..c425ff1 100644
@@ -1617,14 +1617,14 @@ static int calculate_destination_timeout(void)
 		ts_ns = base * mult1 * mult2;
 		ret = ts_ns / 1000;
 	} else {
-		/* 4 bits  0/1 for 10/80us, 3 bits of multiplier */
-		mmr_image = uv_read_local_mmr(UVH_AGING_PRESCALE_SEL);
+		/* 4 bits  0/1 for 10/80us base, 3 bits of multiplier */
+		mmr_image = uv_read_local_mmr(UVH_LB_BAU_MISC_CONTROL);
 		mmr_image = (mmr_image & UV_SA_MASK) >> UV_SA_SHFT;
 		if (mmr_image & (1L << UV2_ACK_UNITS_SHFT))
-			mult1 = 80;
+			base = 80;
 		else
-			mult1 = 10;
-		base = mmr_image & UV2_ACK_MASK;
+			base = 10;
+		mult1 = mmr_image & UV2_ACK_MASK;
 		ret = mult1 * base;
 	}
 	return ret;

@@ -1886,6 +1886,8 @@ static int __init uv_bau_init(void)
 			uv_base_pnode = uv_blade_to_pnode(uvhub);
 	}
 
+	enable_timeouts();
+
 	if (init_per_cpu(nuvhubs, uv_base_pnode)) {
 		nobau = 1;
 		return 0;

@@ -1896,7 +1898,6 @@ static int __init uv_bau_init(void)
 		if (uv_blade_nr_possible_cpus(uvhub))
 			init_uvhub(uvhub, vector, uv_base_pnode);
 
-	enable_timeouts();
 	alloc_intr_gate(vector, uv_bau_message_intr1);
 
 	for_each_possible_blade(uvhub) {

Index: 120113.linux-3.2.1/arch/x86/include/asm/uv/uv_bau.h
===================================================================
@@ -167,6 +167,7 @@
 #define FLUSH_RETRY_TIMEOUT		2
 #define FLUSH_GIVEUP			3
 #define FLUSH_COMPLETE			4
+#define FLUSH_RETRY_BUSYBUG		5
 
 /*
  * tuning the action when the numalink network is extremely delayed

@@ -463,7 +464,6 @@ struct bau_pq_entry {
 struct msg_desc {
 	struct bau_pq_entry	*msg;
 	int			msg_slot;
-	int			swack_slot;
 	struct bau_pq_entry	*queue_first;
 	struct bau_pq_entry	*queue_last;
 };

@@ -517,6 +517,9 @@ struct ptc_stats {
 	unsigned long	s_retry_messages;	/* retry broadcasts */
 	unsigned long	s_bau_reenabled;	/* for bau enable/disable */
 	unsigned long	s_bau_disabled;		/* for bau enable/disable */
+	unsigned long	s_uv2_wars;		/* uv2 workaround, perm. busy */
+	unsigned long	s_uv2_wars_hw;		/* uv2 workaround, hiwater */
+	unsigned long	s_uv2_war_waits;	/* uv2 workaround, long waits */
 	/* destination statistics */
 	unsigned long	d_alltlb;		/* times all tlb's on this
 						   cpu were flushed */

@@ -593,6 +596,8 @@ struct bau_control {
 	short			cpus_in_socket;
 	short			cpus_in_uvhub;
 	short			partition_base_pnode;
+	short			using_desc; /* an index, like uvhub_cpu */
+	unsigned int		inuse_map;
 	unsigned short		message_number;
 	unsigned short		uvhub_quiesce;
 	short			socket_acknowledge_count[DEST_Q_SIZE];

@@ -610,6 +615,7 @@ struct bau_control {
 	int			cong_response_us;
 	int			cong_reps;
 	int			cong_period;
+	unsigned long		clocks_per_100_usec;
 	cycles_t		period_time;
 	long			period_requests;
 	struct hub_and_pnode	*thp;

@@ -670,6 +676,11 @@ static inline void write_mmr_sw_ack(unsi
 	uv_write_local_mmr(UVH_LB_BAU_INTD_SOFTWARE_ACKNOWLEDGE_ALIAS, mr);
 }
 
+static inline void write_gmmr_sw_ack(int pnode, unsigned long mr)
+{
+	write_gmmr(pnode, UVH_LB_BAU_INTD_SOFTWARE_ACKNOWLEDGE_ALIAS, mr);
+}
+
 static inline unsigned long read_mmr_sw_ack(void)
 {
 	return read_lmmr(UVH_LB_BAU_INTD_SOFTWARE_ACKNOWLEDGE);

447 lines not on this page · raw message

index 4a46b27..1b82f7e 100644
@@ -167,6 +167,7 @@
 #define FLUSH_RETRY_TIMEOUT		2
 #define FLUSH_GIVEUP			3
 #define FLUSH_COMPLETE			4
+#define FLUSH_RETRY_BUSYBUG		5
 
 /*
  * tuning the action when the numalink network is extremely delayed

@@ -463,7 +464,6 @@ struct bau_pq_entry {
 struct msg_desc {
 	struct bau_pq_entry	*msg;
 	int			msg_slot;
-	int			swack_slot;
 	struct bau_pq_entry	*queue_first;
 	struct bau_pq_entry	*queue_last;
 };

@@ -517,6 +517,9 @@ struct ptc_stats {
 	unsigned long	s_retry_messages;	/* retry broadcasts */
 	unsigned long	s_bau_reenabled;	/* for bau enable/disable */
 	unsigned long	s_bau_disabled;		/* for bau enable/disable */
+	unsigned long	s_uv2_wars;		/* uv2 workaround, perm. busy */
+	unsigned long	s_uv2_wars_hw;		/* uv2 workaround, hiwater */
+	unsigned long	s_uv2_war_waits;	/* uv2 workaround, long waits */
 	/* destination statistics */
 	unsigned long	d_alltlb;		/* times all tlb's on this
 						   cpu were flushed */

@@ -593,6 +596,8 @@ struct bau_control {
 	short			cpus_in_socket;
 	short			cpus_in_uvhub;
 	short			partition_base_pnode;
+	short			using_desc; /* an index, like uvhub_cpu */
+	unsigned int		inuse_map;
 	unsigned short		message_number;
 	unsigned short		uvhub_quiesce;
 	short			socket_acknowledge_count[DEST_Q_SIZE];

@@ -610,6 +615,7 @@ struct bau_control {
 	int			cong_response_us;
 	int			cong_reps;
 	int			cong_period;
+	unsigned long		clocks_per_100_usec;
 	cycles_t		period_time;
 	long			period_requests;
 	struct hub_and_pnode	*thp;

@@ -670,6 +676,11 @@ static inline void write_mmr_sw_ack(unsigned long mr)
 	uv_write_local_mmr(UVH_LB_BAU_INTD_SOFTWARE_ACKNOWLEDGE_ALIAS, mr);
 }
 
+static inline void write_gmmr_sw_ack(int pnode, unsigned long mr)
+{
+	write_gmmr(pnode, UVH_LB_BAU_INTD_SOFTWARE_ACKNOWLEDGE_ALIAS, mr);
+}
+
 static inline unsigned long read_mmr_sw_ack(void)
 {
 	return read_lmmr(UVH_LB_BAU_INTD_SOFTWARE_ACKNOWLEDGE);

447 lines not on this page · raw message

Index: 120113.linux-3.2.1/arch/x86/platform/uv/tlb_uv.c
===================================================================
@@ -642,16 +642,6 @@ static int uv2_wait_completion(struct ba
 		} else if (descriptor_stat == UV2H_DESC_DEST_TIMEOUT) {
 			stat->s_dtimeout++;
 			ttm = get_cycles();
-			/*
-			 * Our retries may be blocked by all destination
-			 * swack resources being consumed, and a timeout
-			 * pending.  In that case hardware returns the
-			 * ERROR that looks like a destination timeout.
-			 */
-			if (cycles_2_us(ttm - bcp->send_message) < timeout_us) {
-				bcp->conseccompletes = 0;
-				return FLUSH_RETRY_PLUGGED;
-			}
 			bcp->conseccompletes = 0;
 			return FLUSH_RETRY_TIMEOUT;
 		} else {

index 9010ca7..affea50 100644
@@ -642,16 +642,6 @@ static int uv2_wait_completion(struct bau_desc *bau_desc,
 		} else if (descriptor_stat == UV2H_DESC_DEST_TIMEOUT) {
 			stat->s_dtimeout++;
 			ttm = get_cycles();
-			/*
-			 * Our retries may be blocked by all destination
-			 * swack resources being consumed, and a timeout
-			 * pending.  In that case hardware returns the
-			 * ERROR that looks like a destination timeout.
-			 */
-			if (cycles_2_us(ttm - bcp->send_message) < timeout_us) {
-				bcp->conseccompletes = 0;
-				return FLUSH_RETRY_PLUGGED;
-			}
 			bcp->conseccompletes = 0;
 			return FLUSH_RETRY_TIMEOUT;
 		} else {

Index: 120113.linux-3.2.1/arch/x86/platform/uv/tlb_uv.c
===================================================================
@@ -1218,6 +1218,7 @@ void uv_bau_message_interrupt(struct pt_
 	struct ptc_stats *stat;
 	struct msg_desc msgdesc;
 
+	ack_APIC_irq();
 	time_start = get_cycles();
 
 	bcp = &per_cpu(bau_control, smp_processor_id());

@@ -1247,8 +1248,6 @@ void uv_bau_message_interrupt(struct pt_
 		stat->d_nomsg++;
 	else if (count > 1)
 		stat->d_multmsg++;
-
-	ack_APIC_irq();
 }
 
 /*

index affea50..4686bf1 100644
@@ -1218,6 +1218,7 @@ void uv_bau_message_interrupt(struct pt_regs *regs)
 	struct ptc_stats *stat;
 	struct msg_desc msgdesc;
 
+	ack_APIC_irq();
 	time_start = get_cycles();
 
 	bcp = &per_cpu(bau_control, smp_processor_id());

@@ -1247,8 +1248,6 @@ void uv_bau_message_interrupt(struct pt_regs *regs)
 		stat->d_nomsg++;
 	else if (count > 1)
 		stat->d_multmsg++;
-
-	ack_APIC_irq();
 }
 
 /*

Index: 120113.linux-3.2.1/arch/x86/include/asm/uv/uv_bau.h
===================================================================
@@ -483,6 +483,7 @@ struct ptc_stats {
 						   requests */
 	unsigned long	s_stimeout;		/* source side timeouts */
 	unsigned long	s_dtimeout;		/* destination side timeouts */
+	unsigned long	s_strongnacks;		/* number of strong nack's */
 	unsigned long	s_time;			/* time spent in sending side */
 	unsigned long	s_retriesok;		/* successful retries */
 	unsigned long	s_ntargcpu;		/* total number of cpu's

Index: 120113.linux-3.2.1/arch/x86/platform/uv/tlb_uv.c
===================================================================
@@ -635,13 +635,15 @@ static int uv2_wait_completion(struct ba
 		 * our message and its state will stay IDLE.
 		 */
 		if ((descriptor_stat == UV2H_DESC_SOURCE_TIMEOUT) ||
-		    (descriptor_stat == UV2H_DESC_DEST_STRONG_NACK) ||
 		    (descriptor_stat == UV2H_DESC_DEST_PUT_ERR)) {
 			stat->s_stimeout++;
 			return FLUSH_GIVEUP;
+		} else if (descriptor_stat == UV2H_DESC_DEST_STRONG_NACK) {
+			stat->s_strongnacks++;
+			bcp->conseccompletes = 0;
+			return FLUSH_GIVEUP;
 		} else if (descriptor_stat == UV2H_DESC_DEST_TIMEOUT) {
 			stat->s_dtimeout++;
-			ttm = get_cycles();
 			bcp->conseccompletes = 0;
 			return FLUSH_RETRY_TIMEOUT;
 		} else {

@@ -1346,7 +1348,7 @@ static int ptc_seq_show(struct seq_file
 		seq_printf(file,
 			"remotehub numuvhubs numuvhubs16 numuvhubs8 ");
 		seq_printf(file,
-			"numuvhubs4 numuvhubs2 numuvhubs1 dto retries rok ");
+		    "numuvhubs4 numuvhubs2 numuvhubs1 dto snacks retries rok ");
 		seq_printf(file,
 			"resetp resett giveup sto bz throt swack recv rtime ");
 		seq_printf(file,

@@ -1364,10 +1366,10 @@ static int ptc_seq_show(struct seq_file
 			   stat->s_ntargremotes, stat->s_ntargcpu,
 			   stat->s_ntarglocaluvhub, stat->s_ntargremoteuvhub,
 			   stat->s_ntarguvhub, stat->s_ntarguvhub16);
-		seq_printf(file, "%ld %ld %ld %ld %ld ",
+		seq_printf(file, "%ld %ld %ld %ld %ld %ld ",
 			   stat->s_ntarguvhub8, stat->s_ntarguvhub4,
 			   stat->s_ntarguvhub2, stat->s_ntarguvhub1,
-			   stat->s_dtimeout);
+			   stat->s_dtimeout, stat->s_strongnacks);
 		seq_printf(file, "%ld %ld %ld %ld %ld %ld %ld %ld ",
 			   stat->s_retry_messages, stat->s_retriesok,
 			   stat->s_resets_plug, stat->s_resets_timeout,

index 1b82f7e..becf47b 100644
@@ -483,6 +483,7 @@ struct ptc_stats {
 						   requests */
 	unsigned long	s_stimeout;		/* source side timeouts */
 	unsigned long	s_dtimeout;		/* destination side timeouts */
+	unsigned long	s_strongnacks;		/* number of strong nack's */
 	unsigned long	s_time;			/* time spent in sending side */
 	unsigned long	s_retriesok;		/* successful retries */
 	unsigned long	s_ntargcpu;		/* total number of cpu's

index 4686bf1..9be4cff 100644
@@ -635,13 +635,15 @@ static int uv2_wait_completion(struct bau_desc *bau_desc,
 		 * our message and its state will stay IDLE.
 		 */
 		if ((descriptor_stat == UV2H_DESC_SOURCE_TIMEOUT) ||
-		    (descriptor_stat == UV2H_DESC_DEST_STRONG_NACK) ||
 		    (descriptor_stat == UV2H_DESC_DEST_PUT_ERR)) {
 			stat->s_stimeout++;
 			return FLUSH_GIVEUP;
+		} else if (descriptor_stat == UV2H_DESC_DEST_STRONG_NACK) {
+			stat->s_strongnacks++;
+			bcp->conseccompletes = 0;
+			return FLUSH_GIVEUP;
 		} else if (descriptor_stat == UV2H_DESC_DEST_TIMEOUT) {
 			stat->s_dtimeout++;
-			ttm = get_cycles();
 			bcp->conseccompletes = 0;
 			return FLUSH_RETRY_TIMEOUT;
 		} else {

@@ -1346,7 +1348,7 @@ static int ptc_seq_show(struct seq_file *file, void *data)
 		seq_printf(file,
 			"remotehub numuvhubs numuvhubs16 numuvhubs8 ");
 		seq_printf(file,
-			"numuvhubs4 numuvhubs2 numuvhubs1 dto retries rok ");
+		    "numuvhubs4 numuvhubs2 numuvhubs1 dto snacks retries rok ");
 		seq_printf(file,
 			"resetp resett giveup sto bz throt swack recv rtime ");
 		seq_printf(file,

@@ -1364,10 +1366,10 @@ static int ptc_seq_show(struct seq_file *file, void *data)
 			   stat->s_ntargremotes, stat->s_ntargcpu,
 			   stat->s_ntarglocaluvhub, stat->s_ntargremoteuvhub,
 			   stat->s_ntarguvhub, stat->s_ntarguvhub16);
-		seq_printf(file, "%ld %ld %ld %ld %ld ",
+		seq_printf(file, "%ld %ld %ld %ld %ld %ld ",
 			   stat->s_ntarguvhub8, stat->s_ntarguvhub4,
 			   stat->s_ntarguvhub2, stat->s_ntarguvhub1,
-			   stat->s_dtimeout);
+			   stat->s_dtimeout, stat->s_strongnacks);
 		seq_printf(file, "%ld %ld %ld %ld %ld %ld %ld %ld ",
 			   stat->s_retry_messages, stat->s_retriesok,
 			   stat->s_resets_plug, stat->s_resets_timeout,