1 files changed, 515 insertions, 446 deletions

diff --git a/drivers/net/tile/tilepro.c b/drivers/net/tile/tilepro.c
index f9012992d21e..0825db6d883f 100644
--- a/drivers/net/tile/tilepro.c
+++ b/drivers/net/tile/tilepro.c
@@ -1,5 +1,5 @@
 /*
- * Copyright 2010 Tilera Corporation. All Rights Reserved.
+ * Copyright 2011 Tilera Corporation. All Rights Reserved.
  *
  *   This program is free software; you can redistribute it and/or
  *   modify it under the terms of the GNU General Public License
@@ -44,10 +44,6 @@
 #include <linux/tcp.h>
 
 
-/* There is no singlethread_cpu, so schedule work on the current cpu. */
-#define singlethread_cpu -1
-
-
 /*
  * First, "tile_net_init_module()" initializes all four "devices" which
  * can be used by linux.
@@ -73,15 +69,16 @@
  * return, knowing we will be called again later.  Otherwise, we
  * reenable the ingress interrupt, and call "napi_complete()".
  *
+ * HACK: Since disabling the ingress interrupt is not reliable, we
+ * ignore the interrupt if the global "active" flag is false.
+ *
  *
  * NOTE: The use of "native_driver" ensures that EPP exists, and that
- * "epp_sendv" is legal, and that "LIPP" is being used.
+ * we are using "LIPP" and "LEPP".
  *
  * NOTE: Failing to free completions for an arbitrarily long time
  * (which is defined to be illegal) does in fact cause bizarre
  * problems.  The "egress_timer" helps prevent this from happening.
- *
- * NOTE: The egress code can be interrupted by the interrupt handler.
  */
 
 
@@ -142,6 +139,7 @@
 MODULE_AUTHOR("Tilera");
 MODULE_LICENSE("GPL");
 
+
 /*
  * Queue of incoming packets for a specific cpu and device.
  *
@@ -177,7 +175,7 @@ struct tile_net_cpu {
         struct tile_netio_queue queue;
         /* Statistics. */
         struct tile_net_stats_t stats;
-        /* ISSUE: Is this needed? */
+        /* True iff NAPI is enabled. */
         bool napi_enabled;
         /* True if this tile has succcessfully registered with the IPP. */
         bool registered;
@@ -200,20 +198,20 @@ struct tile_net_cpu {
 struct tile_net_priv {
         /* Our network device. */
         struct net_device *dev;
-        /* The actual egress queue. */
-        lepp_queue_t *epp_queue;
-        /* Protects "epp_queue->cmd_tail" and "epp_queue->comp_tail" */
-        spinlock_t cmd_lock;
-        /* Protects "epp_queue->comp_head". */
-        spinlock_t comp_lock;
+        /* Pages making up the egress queue. */
+        struct page *eq_pages;
+        /* Address of the actual egress queue. */
+        lepp_queue_t *eq;
+        /* Protects "eq". */
+        spinlock_t eq_lock;
         /* The hypervisor handle for this interface. */
         int hv_devhdl;
         /* The intr bit mask that IDs this device. */
         u32 intr_id;
         /* True iff "tile_net_open_aux()" has succeeded. */
-        int partly_opened;
-        /* True iff "tile_net_open_inner()" has succeeded. */
-        int fully_opened;
+        bool partly_opened;
+        /* True iff the device is "active". */
+        bool active;
         /* Effective network cpus. */
         struct cpumask network_cpus_map;
         /* Number of network cpus. */
@@ -228,6 +226,10 @@ struct tile_net_priv {
         struct tile_net_cpu *cpu[NR_CPUS];
 };
 
+/* Log2 of the number of small pages needed for the egress queue. */
+#define EQ_ORDER  get_order(sizeof(lepp_queue_t))
+/* Size of the egress queue's pages. */
+#define EQ_SIZE   (1 << (PAGE_SHIFT + EQ_ORDER))
 
 /*
  * The actual devices (xgbe0, xgbe1, gbe0, gbe1).
@@ -284,7 +286,11 @@ static void net_printk(char *fmt, ...)
  */
 static void dump_packet(unsigned char *data, unsigned long length, char *s)
 {
+        int my_cpu = smp_processor_id();
+
         unsigned long i;
+        char buf[128];
+
         static unsigned int count;
 
         pr_info("dump_packet(data %p, length 0x%lx s %s count 0x%x)\n",
@@ -294,10 +300,12 @@ static void dump_packet(unsigned char *data, unsigned long length, char *s)
 
         for (i = 0; i < length; i++) {
                 if ((i & 0xf) == 0)
-                        sprintf(buf, "%8.8lx:", i);
+                        sprintf(buf, "[%02d] %8.8lx:", my_cpu, i);
                 sprintf(buf + strlen(buf), " %2.2x", data[i]);
-                if ((i & 0xf) == 0xf || i == length - 1)
-                        pr_info("%s\n", buf);
+                if ((i & 0xf) == 0xf || i == length - 1) {
+                        strcat(buf, "\n");
+                        pr_info("%s", buf);
+                }
         }
 }
 #endif
@@ -351,60 +359,109 @@ static void tile_net_provide_linux_buffer(struct tile_net_cpu *info,
 
 /*
  * Provide a linux buffer for LIPP.
+ *
+ * Note that the ACTUAL allocation for each buffer is a "struct sk_buff",
+ * plus a chunk of memory that includes not only the requested bytes, but
+ * also NET_SKB_PAD bytes of initial padding, and a "struct skb_shared_info".
+ *
+ * Note that "struct skb_shared_info" is 88 bytes with 64K pages and
+ * 268 bytes with 4K pages (since the frags[] array needs 18 entries).
+ *
+ * Without jumbo packets, the maximum packet size will be 1536 bytes,
+ * and we use 2 bytes (NET_IP_ALIGN) of padding.  ISSUE: If we told
+ * the hardware to clip at 1518 bytes instead of 1536 bytes, then we
+ * could save an entire cache line, but in practice, we don't need it.
+ *
+ * Since CPAs are 38 bits, and we can only encode the high 31 bits in
+ * a "linux_buffer_t", the low 7 bits must be zero, and thus, we must
+ * align the actual "va" mod 128.
+ *
+ * We assume that the underlying "head" will be aligned mod 64.  Note
+ * that in practice, we have seen "head" NOT aligned mod 128 even when
+ * using 2048 byte allocations, which is surprising.
+ *
+ * If "head" WAS always aligned mod 128, we could change LIPP to
+ * assume that the low SIX bits are zero, and the 7th bit is one, that
+ * is, align the actual "va" mod 128 plus 64, which would be "free".
+ *
+ * For now, the actual "head" pointer points at NET_SKB_PAD bytes of
+ * padding, plus 28 or 92 bytes of extra padding, plus the sk_buff
+ * pointer, plus the NET_IP_ALIGN padding, plus 126 or 1536 bytes for
+ * the actual packet, plus 62 bytes of empty padding, plus some
+ * padding and the "struct skb_shared_info".
+ *
+ * With 64K pages, a large buffer thus needs 32+92+4+2+1536+62+88
+ * bytes, or 1816 bytes, which fits comfortably into 2048 bytes.
+ *
+ * With 64K pages, a small buffer thus needs 32+92+4+2+126+88
+ * bytes, or 344 bytes, which means we are wasting 64+ bytes, and
+ * could presumably increase the size of small buffers.
+ *
+ * With 4K pages, a large buffer thus needs 32+92+4+2+1536+62+268
+ * bytes, or 1996 bytes, which fits comfortably into 2048 bytes.
+ *
+ * With 4K pages, a small buffer thus needs 32+92+4+2+126+268
+ * bytes, or 524 bytes, which is annoyingly wasteful.
+ *
+ * Maybe we should increase LIPP_SMALL_PACKET_SIZE to 192?
+ *
+ * ISSUE: Maybe we should increase "NET_SKB_PAD" to 64?
  */
 static bool tile_net_provide_needed_buffer(struct tile_net_cpu *info,
                                            bool small)
 {
-        /* ISSUE: What should we use here? */
+#if TILE_NET_MTU <= 1536
+        /* Without "jumbo", 2 + 1536 should be sufficient. */
+        unsigned int large_size = NET_IP_ALIGN + 1536;
+#else
+        /* ISSUE: This has not been tested. */
         unsigned int large_size = NET_IP_ALIGN + TILE_NET_MTU + 100;
+#endif
 
-        /* Round up to ensure to avoid "false sharing" with last cache line. */
-        unsigned int buffer_size =
+        /* Avoid "false sharing" with last cache line. */
+        /* ISSUE: This is already done by "dev_alloc_skb()". */
+        unsigned int len =
                  (((small ? LIPP_SMALL_PACKET_SIZE : large_size) +
                    CHIP_L2_LINE_SIZE() - 1) & -CHIP_L2_LINE_SIZE());
 
-        /*
-         * ISSUE: Since CPAs are 38 bits, and we can only encode the
-         * high 31 bits in a "linux_buffer_t", the low 7 bits must be
-         * zero, and thus, we must align the actual "va" mod 128.
-         */
-        const unsigned long align = 128;
+        unsigned int padding = 128 - NET_SKB_PAD;
+        unsigned int align;
 
         struct sk_buff *skb;
         void *va;
 
         struct sk_buff **skb_ptr;
 
-        /* Note that "dev_alloc_skb()" adds NET_SKB_PAD more bytes, */
-        /* and also "reserves" that many bytes. */
-        /* ISSUE: Can we "share" the NET_SKB_PAD bytes with "skb_ptr"? */
-        int len = sizeof(*skb_ptr) + align + buffer_size;
-
-        while (1) {
-
-                /* Allocate (or fail). */
-                skb = dev_alloc_skb(len);
-                if (skb == NULL)
-                        return false;
-
-                /* Make room for a back-pointer to 'skb'. */
-                skb_reserve(skb, sizeof(*skb_ptr));
+        /* Request 96 extra bytes for alignment purposes. */
+        skb = dev_alloc_skb(len + padding);
+        if (skb == NULL)
+                return false;
 
-                /* Make sure we are aligned. */
-                skb_reserve(skb, -(long)skb->data & (align - 1));
+        /* Skip 32 or 96 bytes to align "data" mod 128. */
+        align = -(long)skb->data & (128 - 1);
+        BUG_ON(align > padding);
+        skb_reserve(skb, align);
 
-                /* This address is given to IPP. */
-                va = skb->data;
+        /* This address is given to IPP. */
+        va = skb->data;
 
-                if (small)
-                        break;
+        /* Buffers must not span a huge page. */
+        BUG_ON(((((long)va & ~HPAGE_MASK) + len) & HPAGE_MASK) != 0);
 
-                /* ISSUE: This has never been observed! */
-                /* Large buffers must not span a huge page. */
-                if (((((long)va & ~HPAGE_MASK) + 1535) & HPAGE_MASK) == 0)
-                        break;
-                pr_err("Leaking unaligned linux buffer at %p.\n", va);
+#ifdef TILE_NET_PARANOIA
+#if CHIP_HAS_CBOX_HOME_MAP()
+        if (hash_default) {
+                HV_PTE pte = *virt_to_pte(current->mm, (unsigned long)va);
+                if (hv_pte_get_mode(pte) != HV_PTE_MODE_CACHE_HASH_L3)
+                        panic("Non-HFH ingress buffer! VA=%p Mode=%d PTE=%llx",
+                              va, hv_pte_get_mode(pte), hv_pte_val(pte));
         }
+#endif
+#endif
+
+        /* Invalidate the packet buffer. */
+        if (!hash_default)
+                __inv_buffer(va, len);
 
         /* Skip two bytes to satisfy LIPP assumptions. */
         /* Note that this aligns IP on a 16 byte boundary. */
@@ -415,23 +472,9 @@ static bool tile_net_provide_needed_buffer(struct tile_net_cpu *info,
         skb_ptr = va - sizeof(*skb_ptr);
         *skb_ptr = skb;
 
-        /* Invalidate the packet buffer. */
-        if (!hash_default)
-                __inv_buffer(skb->data, buffer_size);
-
         /* Make sure "skb_ptr" has been flushed. */
         __insn_mf();
 
-#ifdef TILE_NET_PARANOIA
-#if CHIP_HAS_CBOX_HOME_MAP()
-        if (hash_default) {
-                HV_PTE pte = *virt_to_pte(current->mm, (unsigned long)va);
-                if (hv_pte_get_mode(pte) != HV_PTE_MODE_CACHE_HASH_L3)
-                        panic("Non-coherent ingress buffer!");
-        }
-#endif
-#endif
-
         /* Provide the new buffer. */
         tile_net_provide_linux_buffer(info, va, small);
 
@@ -469,48 +512,64 @@ oops:
  * Grab some LEPP completions, and store them in "comps", of size
  * "comps_size", and return the number of completions which were
  * stored, so the caller can free them.
- *
- * If "pending" is not NULL, it will be set to true if there might
- * still be some pending completions caused by this tile, else false.
  */
-static unsigned int tile_net_lepp_grab_comps(struct net_device *dev,
+static unsigned int tile_net_lepp_grab_comps(lepp_queue_t *eq,
                                              struct sk_buff *comps[],
                                              unsigned int comps_size,
-                                             bool *pending)
+                                             unsigned int min_size)
 {
-        struct tile_net_priv *priv = netdev_priv(dev);
-
-        lepp_queue_t *eq = priv->epp_queue;
-
         unsigned int n = 0;
 
-        unsigned int comp_head;
-        unsigned int comp_busy;
-        unsigned int comp_tail;
-
-        spin_lock(&priv->comp_lock);
-
-        comp_head = eq->comp_head;
-        comp_busy = eq->comp_busy;
-        comp_tail = eq->comp_tail;
+        unsigned int comp_head = eq->comp_head;
+        unsigned int comp_busy = eq->comp_busy;
 
         while (comp_head != comp_busy && n < comps_size) {
                 comps[n++] = eq->comps[comp_head];
                 LEPP_QINC(comp_head);
         }
 
-        if (pending != NULL)
-                *pending = (comp_head != comp_tail);
+        if (n < min_size)
+                return 0;
 
         eq->comp_head = comp_head;
 
-        spin_unlock(&priv->comp_lock);
-
         return n;
 }
 
 
 /*
+ * Free some comps, and return true iff there are still some pending.
+ */
+static bool tile_net_lepp_free_comps(struct net_device *dev, bool all)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+
+        lepp_queue_t *eq = priv->eq;
+
+        struct sk_buff *olds[64];
+        unsigned int wanted = 64;
+        unsigned int i, n;
+        bool pending;
+
+        spin_lock(&priv->eq_lock);
+
+        if (all)
+                eq->comp_busy = eq->comp_tail;
+
+        n = tile_net_lepp_grab_comps(eq, olds, wanted, 0);
+
+        pending = (eq->comp_head != eq->comp_tail);
+
+        spin_unlock(&priv->eq_lock);
+
+        for (i = 0; i < n; i++)
+                kfree_skb(olds[i]);
+
+        return pending;
+}
+
+
+/*
  * Make sure the egress timer is scheduled.
  *
  * Note that we use "schedule if not scheduled" logic instead of the more
@@ -544,21 +603,11 @@ static void tile_net_handle_egress_timer(unsigned long arg)
         struct tile_net_cpu *info = (struct tile_net_cpu *)arg;
         struct net_device *dev = info->napi.dev;
 
-        struct sk_buff *olds[32];
-        unsigned int wanted = 32;
-        unsigned int i, nolds = 0;
-        bool pending;
-
         /* The timer is no longer scheduled. */
         info->egress_timer_scheduled = false;
 
-        nolds = tile_net_lepp_grab_comps(dev, olds, wanted, &pending);
-
-        for (i = 0; i < nolds; i++)
-                kfree_skb(olds[i]);
-
-        /* Reschedule timer if needed. */
-        if (pending)
+        /* Free comps, and reschedule timer if more are pending. */
+        if (tile_net_lepp_free_comps(dev, false))
                 tile_net_schedule_egress_timer(info);
 }
 
@@ -636,8 +685,39 @@ static bool is_dup_ack(char *s1, char *s2, unsigned int len)
 
 
 
+static void tile_net_discard_aux(struct tile_net_cpu *info, int index)
+{
+        struct tile_netio_queue *queue = &info->queue;
+        netio_queue_impl_t *qsp = queue->__system_part;
+        netio_queue_user_impl_t *qup = &queue->__user_part;
+
+        int index2_aux = index + sizeof(netio_pkt_t);
+        int index2 =
+                ((index2_aux ==
+                  qsp->__packet_receive_queue.__last_packet_plus_one) ?
+                 0 : index2_aux);
+
+        netio_pkt_t *pkt = (netio_pkt_t *)((unsigned long) &qsp[1] + index);
+
+        /* Extract the "linux_buffer_t". */
+        unsigned int buffer = pkt->__packet.word;
+
+        /* Convert "linux_buffer_t" to "va". */
+        void *va = __va((phys_addr_t)(buffer >> 1) << 7);
+
+        /* Acquire the associated "skb". */
+        struct sk_buff **skb_ptr = va - sizeof(*skb_ptr);
+        struct sk_buff *skb = *skb_ptr;
+
+        kfree_skb(skb);
+
+        /* Consume this packet. */
+        qup->__packet_receive_read = index2;
+}
+
+
 /*
- * Like "tile_net_handle_packets()", but just discard packets.
+ * Like "tile_net_poll()", but just discard packets.
  */
 static void tile_net_discard_packets(struct net_device *dev)
 {
@@ -650,32 +730,8 @@ static void tile_net_discard_packets(struct net_device *dev)
 
         while (qup->__packet_receive_read !=
                qsp->__packet_receive_queue.__packet_write) {
-
                 int index = qup->__packet_receive_read;
-
-                int index2_aux = index + sizeof(netio_pkt_t);
-                int index2 =
-                        ((index2_aux ==
-                          qsp->__packet_receive_queue.__last_packet_plus_one) ?
-                         0 : index2_aux);
-
-                netio_pkt_t *pkt = (netio_pkt_t *)
-                        ((unsigned long) &qsp[1] + index);
-
-                /* Extract the "linux_buffer_t". */
-                unsigned int buffer = pkt->__packet.word;
-
-                /* Convert "linux_buffer_t" to "va". */
-                void *va = __va((phys_addr_t)(buffer >> 1) << 7);
-
-                /* Acquire the associated "skb". */
-                struct sk_buff **skb_ptr = va - sizeof(*skb_ptr);
-                struct sk_buff *skb = *skb_ptr;
-
-                kfree_skb(skb);
-
-                /* Consume this packet. */
-                qup->__packet_receive_read = index2;
+                tile_net_discard_aux(info, index);
         }
 }
 
@@ -704,7 +760,8 @@ static bool tile_net_poll_aux(struct tile_net_cpu *info, int index)
 
         netio_pkt_metadata_t *metadata = NETIO_PKT_METADATA(pkt);
 
-        /* Extract the packet size. */
+        /* Extract the packet size.  FIXME: Shouldn't the second line */
+        /* get subtracted?  Mostly moot, since it should be "zero". */
         unsigned long len =
                 (NETIO_PKT_CUSTOM_LENGTH(pkt) +
                  NET_IP_ALIGN - NETIO_PACKET_PADDING);
@@ -722,15 +779,6 @@ static bool tile_net_poll_aux(struct tile_net_cpu *info, int index)
         /* Compare to "NETIO_PKT_CUSTOM_DATA(pkt)". */
         unsigned char *buf = va + NET_IP_ALIGN;
 
-#ifdef IGNORE_DUP_ACKS
-
-        static int other;
-        static int final;
-        static int keep;
-        static int skip;
-
-#endif
-
         /* Invalidate the packet buffer. */
         if (!hash_default)
                 __inv_buffer(buf, len);
@@ -745,16 +793,8 @@ static bool tile_net_poll_aux(struct tile_net_cpu *info, int index)
 #ifdef TILE_NET_VERIFY_INGRESS
         if (!NETIO_PKT_L4_CSUM_CORRECT_M(metadata, pkt) &&
             NETIO_PKT_L4_CSUM_CALCULATED_M(metadata, pkt)) {
-                /*
-                 * FIXME: This complains about UDP packets
-                 * with a "zero" checksum (bug 6624).
-                 */
-#ifdef TILE_NET_PANIC_ON_BAD
-                dump_packet(buf, len, "rx");
-                panic("Bad L4 checksum.");
-#else
+                /* Bug 6624: Includes UDP packets with a "zero" checksum. */
                 pr_warning("Bad L4 checksum on %d byte packet.\n", len);
-#endif
         }
         if (!NETIO_PKT_L3_CSUM_CORRECT_M(metadata, pkt) &&
             NETIO_PKT_L3_CSUM_CALCULATED_M(metadata, pkt)) {
@@ -769,90 +809,29 @@ static bool tile_net_poll_aux(struct tile_net_cpu *info, int index)
                 }
                 break;
         case NETIO_PKT_STATUS_BAD:
-#ifdef TILE_NET_PANIC_ON_BAD
-                dump_packet(buf, len, "rx");
-                panic("Unexpected BAD packet.");
-#else
-                pr_warning("Unexpected BAD %d byte packet.\n", len);
-#endif
+                pr_warning("Unexpected BAD %ld byte packet.\n", len);
         }
 #endif
 
         filter = 0;
 
+        /* ISSUE: Filter TCP packets with "bad" checksums? */
+
         if (!(dev->flags & IFF_UP)) {
                 /* Filter packets received before we're up. */
                 filter = 1;
+        } else if (NETIO_PKT_STATUS_M(metadata, pkt) == NETIO_PKT_STATUS_BAD) {
+                /* Filter "truncated" packets. */
+                filter = 1;
         } else if (!(dev->flags & IFF_PROMISC)) {
-                /*
-                 * FIXME: Implement HW multicast filter.
-                 */
-                if (is_unicast_ether_addr(buf)) {
+                /* FIXME: Implement HW multicast filter. */
+                if (!is_multicast_ether_addr(buf)) {
                         /* Filter packets not for our address. */
                         const u8 *mine = dev->dev_addr;
                         filter = compare_ether_addr(mine, buf);
                 }
         }
 
-#ifdef IGNORE_DUP_ACKS
-
-        if (len != 66) {
-                /* FIXME: Must check "is_tcp_ack(buf, len)" somehow. */
-
-                other++;
-
-        } else if (index2 ==
-                   qsp->__packet_receive_queue.__packet_write) {
-
-                final++;
-
-        } else {
-
-                netio_pkt_t *pkt2 = (netio_pkt_t *)
-                        ((unsigned long) &qsp[1] + index2);
-
-                netio_pkt_metadata_t *metadata2 =
-                        NETIO_PKT_METADATA(pkt2);
-
-                /* Extract the packet size. */
-                unsigned long len2 =
-                        (NETIO_PKT_CUSTOM_LENGTH(pkt2) +
-                         NET_IP_ALIGN - NETIO_PACKET_PADDING);
-
-                if (len2 == 66 &&
-                    NETIO_PKT_FLOW_HASH_M(metadata, pkt) ==
-                    NETIO_PKT_FLOW_HASH_M(metadata2, pkt2)) {
-
-                        /* Extract the "linux_buffer_t". */
-                        unsigned int buffer2 = pkt2->__packet.word;
-
-                        /* Convert "linux_buffer_t" to "va". */
-                        void *va2 =
-                                __va((phys_addr_t)(buffer2 >> 1) << 7);
-
-                        /* Extract the packet data pointer. */
-                        /* Compare to "NETIO_PKT_CUSTOM_DATA(pkt)". */
-                        unsigned char *buf2 = va2 + NET_IP_ALIGN;
-
-                        /* Invalidate the packet buffer. */
-                        if (!hash_default)
-                                __inv_buffer(buf2, len2);
-
-                        if (is_dup_ack(buf, buf2, len)) {
-                                skip++;
-                                filter = 1;
-                        } else {
-                                keep++;
-                        }
-                }
-        }
-
-        if (net_ratelimit())
-                pr_info("Other %d Final %d Keep %d Skip %d.\n",
-                        other, final, keep, skip);
-
-#endif
-
         if (filter) {
 
                 /* ISSUE: Update "drop" statistics? */
@@ -877,10 +856,7 @@ static bool tile_net_poll_aux(struct tile_net_cpu *info, int index)
                 /* NOTE: This call also sets "skb->dev = dev". */
                 skb->protocol = eth_type_trans(skb, dev);
 
-                /* ISSUE: Discard corrupt packets? */
-                /* ISSUE: Discard packets with bad checksums? */
-
-                /* Avoid recomputing TCP/UDP checksums. */
+                /* Avoid recomputing "good" TCP/UDP checksums. */
                 if (NETIO_PKT_L4_CSUM_CORRECT_M(metadata, pkt))
                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 
@@ -912,9 +888,14 @@ static bool tile_net_poll_aux(struct tile_net_cpu *info, int index)
 /*
  * Handle some packets for the given device on the current CPU.
  *
- * ISSUE: The "rotting packet" race condition occurs if a packet
- * arrives after the queue appears to be empty, and before the
- * hypervisor interrupt is re-enabled.
+ * If "tile_net_stop()" is called on some other tile while this
+ * function is running, we will return, hopefully before that
+ * other tile asks us to call "napi_disable()".
+ *
+ * The "rotting packet" race condition occurs if a packet arrives
+ * during the extremely narrow window between the queue appearing to
+ * be empty, and the ingress interrupt being re-enabled.  This happens
+ * a LOT under heavy network load.
  */
 static int tile_net_poll(struct napi_struct *napi, int budget)
 {
@@ -928,7 +909,7 @@ static int tile_net_poll(struct napi_struct *napi, int budget)
 
         unsigned int work = 0;
 
-        while (1) {
+        while (priv->active) {
                 int index = qup->__packet_receive_read;
                 if (index == qsp->__packet_receive_queue.__packet_write)
                         break;
@@ -941,19 +922,24 @@ static int tile_net_poll(struct napi_struct *napi, int budget)
 
         napi_complete(&info->napi);
 
-        /* Re-enable hypervisor interrupts. */
+        if (!priv->active)
+                goto done;
+
+        /* Re-enable the ingress interrupt. */
         enable_percpu_irq(priv->intr_id);
 
-        /* HACK: Avoid the "rotting packet" problem. */
+        /* HACK: Avoid the "rotting packet" problem (see above). */
         if (qup->__packet_receive_read !=
-            qsp->__packet_receive_queue.__packet_write)
-                napi_schedule(&info->napi);
-
-        /* ISSUE: Handle completions? */
+            qsp->__packet_receive_queue.__packet_write) {
+                /* ISSUE: Sometimes this returns zero, presumably */
+                /* because an interrupt was handled for this tile. */
+                (void)napi_reschedule(&info->napi);
+        }
 
 done:
 
-        tile_net_provide_needed_buffers(info);
+        if (priv->active)
+                tile_net_provide_needed_buffers(info);
 
         return work;
 }
@@ -961,6 +947,12 @@ done:
 
 /*
  * Handle an ingress interrupt for the given device on the current cpu.
+ *
+ * ISSUE: Sometimes this gets called after "disable_percpu_irq()" has
+ * been called!  This is probably due to "pending hypervisor downcalls".
+ *
+ * ISSUE: Is there any race condition between the "napi_schedule()" here
+ * and the "napi_complete()" call above?
  */
 static irqreturn_t tile_net_handle_ingress_interrupt(int irq, void *dev_ptr)
 {
@@ -969,9 +961,15 @@ static irqreturn_t tile_net_handle_ingress_interrupt(int irq, void *dev_ptr)
         int my_cpu = smp_processor_id();
         struct tile_net_cpu *info = priv->cpu[my_cpu];
 
-        /* Disable hypervisor interrupt. */
+        /* Disable the ingress interrupt. */
         disable_percpu_irq(priv->intr_id);
 
+        /* Ignore unwanted interrupts. */
+        if (!priv->active)
+                return IRQ_HANDLED;
+
+        /* ISSUE: Sometimes "info->napi_enabled" is false here. */
+
         napi_schedule(&info->napi);
 
         return IRQ_HANDLED;
@@ -1005,8 +1003,7 @@ static int tile_net_open_aux(struct net_device *dev)
          */
         {
                 int epp_home = hv_lotar_to_cpu(epp_lotar);
-                struct page *page = virt_to_page(priv->epp_queue);
-                homecache_change_page_home(page, 0, epp_home);
+                homecache_change_page_home(priv->eq_pages, EQ_ORDER, epp_home);
         }
 
         /*
@@ -1015,9 +1012,9 @@ static int tile_net_open_aux(struct net_device *dev)
         {
                 netio_ipp_address_t ea = {
                         .va = 0,
-                        .pa = __pa(priv->epp_queue),
+                        .pa = __pa(priv->eq),
                         .pte = hv_pte(0),
-                        .size = PAGE_SIZE,
+                        .size = EQ_SIZE,
                 };
                 ea.pte = hv_pte_set_lotar(ea.pte, epp_lotar);
                 ea.pte = hv_pte_set_mode(ea.pte, HV_PTE_MODE_CACHE_TILE_L3);
@@ -1043,7 +1040,7 @@ static int tile_net_open_aux(struct net_device *dev)
 
 
 /*
- * Register with hypervisor on each CPU.
+ * Register with hypervisor on the current CPU.
  *
  * Strangely, this function does important things even if it "fails",
  * which is especially common if the link is not up yet.  Hopefully
@@ -1092,7 +1089,8 @@ static void tile_net_register(void *dev_ptr)
         priv->cpu[my_cpu] = info;
 
         /*
-         * Register ourselves with the IPP.
+         * Register ourselves with LIPP.  This does a lot of stuff,
+         * including invoking the LIPP registration code.
          */
         ret = hv_dev_pwrite(priv->hv_devhdl, 0,
                             (HV_VirtAddr)&config,
@@ -1101,8 +1099,11 @@ static void tile_net_register(void *dev_ptr)
         PDEBUG("hv_dev_pwrite(NETIO_IPP_INPUT_REGISTER_OFF) returned %d\n",
                ret);
         if (ret < 0) {
-                printk(KERN_DEBUG "hv_dev_pwrite NETIO_IPP_INPUT_REGISTER_OFF"
-                       " failure %d\n", ret);
+                if (ret != NETIO_LINK_DOWN) {
+                        printk(KERN_DEBUG "hv_dev_pwrite "
+                               "NETIO_IPP_INPUT_REGISTER_OFF failure %d\n",
+                               ret);
+                }
                 info->link_down = (ret == NETIO_LINK_DOWN);
                 return;
         }
@@ -1145,15 +1146,47 @@ static void tile_net_register(void *dev_ptr)
                            NETIO_IPP_GET_FASTIO_OFF);
         PDEBUG("hv_dev_pread(NETIO_IPP_GET_FASTIO_OFF) returned %d\n", ret);
 
-        netif_napi_add(dev, &info->napi, tile_net_poll, 64);
-
         /* Now we are registered. */
         info->registered = true;
 }
 
 
 /*
- * Unregister with hypervisor on each CPU.
+ * Deregister with hypervisor on the current CPU.
+ *
+ * This simply discards all our credits, so no more packets will be
+ * delivered to this tile.  There may still be packets in our queue.
+ *
+ * Also, disable the ingress interrupt.
+ */
+static void tile_net_deregister(void *dev_ptr)
+{
+        struct net_device *dev = (struct net_device *)dev_ptr;
+        struct tile_net_priv *priv = netdev_priv(dev);
+        int my_cpu = smp_processor_id();
+        struct tile_net_cpu *info = priv->cpu[my_cpu];
+
+        /* Disable the ingress interrupt. */
+        disable_percpu_irq(priv->intr_id);
+
+        /* Do nothing else if not registered. */
+        if (info == NULL || !info->registered)
+                return;
+
+        {
+                struct tile_netio_queue *queue = &info->queue;
+                netio_queue_user_impl_t *qup = &queue->__user_part;
+
+                /* Discard all our credits. */
+                __netio_fastio_return_credits(qup->__fastio_index, -1);
+        }
+}
+
+
+/*
+ * Unregister with hypervisor on the current CPU.
+ *
+ * Also, disable the ingress interrupt.
  */
 static void tile_net_unregister(void *dev_ptr)
 {
@@ -1162,35 +1195,23 @@ static void tile_net_unregister(void *dev_ptr)
         int my_cpu = smp_processor_id();
         struct tile_net_cpu *info = priv->cpu[my_cpu];
 
-        int ret = 0;
+        int ret;
         int dummy = 0;
 
-        /* Do nothing if never registered. */
-        if (info == NULL)
-                return;
+        /* Disable the ingress interrupt. */
+        disable_percpu_irq(priv->intr_id);
 
-        /* Do nothing if already unregistered. */
-        if (!info->registered)
+        /* Do nothing else if not registered. */
+        if (info == NULL || !info->registered)
                 return;
 
-        /*
-         * Unregister ourselves with LIPP.
-         */
+        /* Unregister ourselves with LIPP/LEPP. */
         ret = hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
                             sizeof(dummy), NETIO_IPP_INPUT_UNREGISTER_OFF);
-        PDEBUG("hv_dev_pwrite(NETIO_IPP_INPUT_UNREGISTER_OFF) returned %d\n",
-               ret);
-        if (ret < 0) {
-                /* FIXME: Just panic? */
-                pr_err("hv_dev_pwrite NETIO_IPP_INPUT_UNREGISTER_OFF"
-                       " failure %d\n", ret);
-        }
+        if (ret < 0)
+                panic("Failed to unregister with LIPP/LEPP!\n");
 
-        /*
-         * Discard all packets still in our NetIO queue.  Hopefully,
-         * once the unregister call is complete, there will be no
-         * packets still in flight on the IDN.
-         */
+        /* Discard all packets still in our NetIO queue. */
         tile_net_discard_packets(dev);
 
         /* Reset state. */
@@ -1200,11 +1221,6 @@ static void tile_net_unregister(void *dev_ptr)
         /* Cancel egress timer. */
         del_timer(&info->egress_timer);
         info->egress_timer_scheduled = false;
-
-        netif_napi_del(&info->napi);
-
-        /* Now we are unregistered. */
-        info->registered = false;
 }
 
 
@@ -1212,18 +1228,28 @@ static void tile_net_unregister(void *dev_ptr)
  * Helper function for "tile_net_stop()".
  *
  * Also used to handle registration failure in "tile_net_open_inner()",
- * when "fully_opened" is known to be false, and the various extra
- * steps in "tile_net_stop()" are not necessary.  ISSUE: It might be
- * simpler if we could just call "tile_net_stop()" anyway.
+ * when the various extra steps in "tile_net_stop()" are not necessary.
  */
 static void tile_net_stop_aux(struct net_device *dev)
 {
         struct tile_net_priv *priv = netdev_priv(dev);
+        int i;
 
         int dummy = 0;
 
-        /* Unregister all tiles, so LIPP will stop delivering packets. */
+        /*
+         * Unregister all tiles, so LIPP will stop delivering packets.
+         * Also, delete all the "napi" objects (sequentially, to protect
+         * "dev->napi_list").
+         */
         on_each_cpu(tile_net_unregister, (void *)dev, 1);
+        for_each_online_cpu(i) {
+                struct tile_net_cpu *info = priv->cpu[i];
+                if (info != NULL && info->registered) {
+                        netif_napi_del(&info->napi);
+                        info->registered = false;
+                }
+        }
 
         /* Stop LIPP/LEPP. */
         if (hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
@@ -1235,18 +1261,15 @@ static void tile_net_stop_aux(struct net_device *dev)
 
 
 /*
- * Disable ingress interrupts for the given device on the current cpu.
+ * Disable NAPI for the given device on the current cpu.
  */
-static void tile_net_disable_intr(void *dev_ptr)
+static void tile_net_stop_disable(void *dev_ptr)
 {
         struct net_device *dev = (struct net_device *)dev_ptr;
         struct tile_net_priv *priv = netdev_priv(dev);
         int my_cpu = smp_processor_id();
         struct tile_net_cpu *info = priv->cpu[my_cpu];
 
-        /* Disable hypervisor interrupt. */
-        disable_percpu_irq(priv->intr_id);
-
         /* Disable NAPI if needed. */
         if (info != NULL && info->napi_enabled) {
                 napi_disable(&info->napi);
@@ -1256,21 +1279,24 @@ static void tile_net_disable_intr(void *dev_ptr)
 
 
 /*
- * Enable ingress interrupts for the given device on the current cpu.
+ * Enable NAPI and the ingress interrupt for the given device
+ * on the current cpu.
+ *
+ * ISSUE: Only do this for "network cpus"?
  */
-static void tile_net_enable_intr(void *dev_ptr)
+static void tile_net_open_enable(void *dev_ptr)
 {
         struct net_device *dev = (struct net_device *)dev_ptr;
         struct tile_net_priv *priv = netdev_priv(dev);
         int my_cpu = smp_processor_id();
         struct tile_net_cpu *info = priv->cpu[my_cpu];
 
-        /* Enable hypervisor interrupt. */
-        enable_percpu_irq(priv->intr_id);
-
         /* Enable NAPI. */
         napi_enable(&info->napi);
         info->napi_enabled = true;
+
+        /* Enable the ingress interrupt. */
+        enable_percpu_irq(priv->intr_id);
 }
 
 
@@ -1288,8 +1314,9 @@ static int tile_net_open_inner(struct net_device *dev)
         int my_cpu = smp_processor_id();
         struct tile_net_cpu *info;
         struct tile_netio_queue *queue;
-        unsigned int irq;
+        int result = 0;
         int i;
+        int dummy = 0;
 
         /*
          * First try to register just on the local CPU, and handle any
@@ -1307,42 +1334,52 @@ static int tile_net_open_inner(struct net_device *dev)
         /*
          * Now register everywhere else.  If any registration fails,
          * even for "link down" (which might not be possible), we
-         * clean up using "tile_net_stop_aux()".
+         * clean up using "tile_net_stop_aux()".  Also, add all the
+         * "napi" objects (sequentially, to protect "dev->napi_list").
+         * ISSUE: Only use "netif_napi_add()" for "network cpus"?
          */
         smp_call_function(tile_net_register, (void *)dev, 1);
         for_each_online_cpu(i) {
-                if (!priv->cpu[i]->registered) {
-                        tile_net_stop_aux(dev);
-                        return -EAGAIN;
-                }
+                struct tile_net_cpu *info = priv->cpu[i];
+                if (info->registered)
+                        netif_napi_add(dev, &info->napi, tile_net_poll, 64);
+                else
+                        result = -EAGAIN;
+        }
+        if (result != 0) {
+                tile_net_stop_aux(dev);
+                return result;
         }
 
         queue = &info->queue;
 
-        /*
-         * Set the device intr bit mask.
-         * The tile_net_register above sets per tile __intr_id.
-         */
-        priv->intr_id = queue->__system_part->__intr_id;
-        BUG_ON(!priv->intr_id);
-
-        /*
-         * Register the device interrupt handler.
-         * The __ffs() function returns the index into the interrupt handler
-         * table from the interrupt bit mask which should have one bit
-         * and one bit only set.
-         */
-        irq = __ffs(priv->intr_id);
-        tile_irq_activate(irq, TILE_IRQ_PERCPU);
-        BUG_ON(request_irq(irq, tile_net_handle_ingress_interrupt,
-                           0, dev->name, (void *)dev) != 0);
+        if (priv->intr_id == 0) {
+                unsigned int irq;
 
-        /* ISSUE: How could "priv->fully_opened" ever be "true" here? */
-
-        if (!priv->fully_opened) {
+                /*
+                 * Acquire the irq allocated by the hypervisor.  Every
+                 * queue gets the same irq.  The "__intr_id" field is
+                 * "1 << irq", so we use "__ffs()" to extract "irq".
+                 */
+                priv->intr_id = queue->__system_part->__intr_id;
+                BUG_ON(priv->intr_id == 0);
+                irq = __ffs(priv->intr_id);
 
-                int dummy = 0;
+                /*
+                 * Register the ingress interrupt handler for this
+                 * device, permanently.
+                 *
+                 * We used to call "free_irq()" in "tile_net_stop()",
+                 * and then re-register the handler here every time,
+                 * but that caused DNP errors in "handle_IRQ_event()"
+                 * because "desc->action" was NULL.  See bug 9143.
+                 */
+                tile_irq_activate(irq, TILE_IRQ_PERCPU);
+                BUG_ON(request_irq(irq, tile_net_handle_ingress_interrupt,
+                                   0, dev->name, (void *)dev) != 0);
+        }
 
+        {
                 /* Allocate initial buffers. */
 
                 int max_buffers =
@@ -1359,18 +1396,21 @@ static int tile_net_open_inner(struct net_device *dev)
                 if (info->num_needed_small_buffers != 0 ||
                     info->num_needed_large_buffers != 0)
                         panic("Insufficient memory for buffer stack!");
+        }
 
-                /* Start LIPP/LEPP and activate "ingress" at the shim. */
-                if (hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
-                                  sizeof(dummy), NETIO_IPP_INPUT_INIT_OFF) < 0)
-                        panic("Failed to activate the LIPP Shim!\n");
+        /* We are about to be active. */
+        priv->active = true;
 
-                priv->fully_opened = 1;
-        }
+        /* Make sure "active" is visible to all tiles. */
+        mb();
 
-        /* On each tile, enable the hypervisor to trigger interrupts. */
-        /* ISSUE: Do this before starting LIPP/LEPP? */
-        on_each_cpu(tile_net_enable_intr, (void *)dev, 1);
+        /* On each tile, enable NAPI and the ingress interrupt. */
+        on_each_cpu(tile_net_open_enable, (void *)dev, 1);
+
+        /* Start LIPP/LEPP and activate "ingress" at the shim. */
+        if (hv_dev_pwrite(priv->hv_devhdl, 0, (HV_VirtAddr)&dummy,
+                          sizeof(dummy), NETIO_IPP_INPUT_INIT_OFF) < 0)
+                panic("Failed to activate the LIPP Shim!\n");
 
         /* Start our transmit queue. */
         netif_start_queue(dev);
@@ -1396,9 +1436,9 @@ static void tile_net_open_retry(struct work_struct *w)
          * ourselves to try again later; otherwise, tell Linux we now have
          * a working link.  ISSUE: What if the return value is negative?
          */
-        if (tile_net_open_inner(priv->dev))
-                schedule_delayed_work_on(singlethread_cpu, &priv->retry_work,
-                                         TILE_NET_RETRY_INTERVAL);
+        if (tile_net_open_inner(priv->dev) != 0)
+                schedule_delayed_work(&priv->retry_work,
+                                      TILE_NET_RETRY_INTERVAL);
         else
                 netif_carrier_on(priv->dev);
 }
@@ -1412,8 +1452,8 @@ static void tile_net_open_retry(struct work_struct *w)
  * The open entry point is called when a network interface is made
  * active by the system (IFF_UP).  At this point all resources needed
  * for transmit and receive operations are allocated, the interrupt
- * handler is registered with the OS, the watchdog timer is started,
- * and the stack is notified that the interface is ready.
+ * handler is registered with the OS (if needed), the watchdog timer
+ * is started, and the stack is notified that the interface is ready.
  *
  * If the actual link is not available yet, then we tell Linux that
  * we have no carrier, and we keep checking until the link comes up.
@@ -1468,6 +1508,10 @@ static int tile_net_open(struct net_device *dev)
 #endif
 
                 priv->partly_opened = 1;
+
+        } else {
+                /* FIXME: Is this possible? */
+                /* printk("Already partly opened.\n"); */
         }
 
         /*
@@ -1487,57 +1531,17 @@ static int tile_net_open(struct net_device *dev)
          * and then remember to try again later.
          */
         netif_carrier_off(dev);
-        schedule_delayed_work_on(singlethread_cpu, &priv->retry_work,
-                                 TILE_NET_RETRY_INTERVAL);
+        schedule_delayed_work(&priv->retry_work, TILE_NET_RETRY_INTERVAL);
 
         return 0;
 }
 
 
-/*
- * Disables a network interface.
- *
- * Returns 0, this is not allowed to fail.
- *
- * The close entry point is called when an interface is de-activated
- * by the OS.  The hardware is still under the drivers control, but
- * needs to be disabled.  A global MAC reset is issued to stop the
- * hardware, and all transmit and receive resources are freed.
- *
- * ISSUE: Can this can be called while "tile_net_poll()" is running?
- */
-static int tile_net_stop(struct net_device *dev)
+static int tile_net_drain_lipp_buffers(struct tile_net_priv *priv)
 {
-        struct tile_net_priv *priv = netdev_priv(dev);
-
-        bool pending = true;
-
-        PDEBUG("tile_net_stop()\n");
-
-        /* ISSUE: Only needed if not yet fully open. */
-        cancel_delayed_work_sync(&priv->retry_work);
-
-        /* Can't transmit any more. */
-        netif_stop_queue(dev);
-
-        /*
-         * Disable hypervisor interrupts on each tile.
-         */
-        on_each_cpu(tile_net_disable_intr, (void *)dev, 1);
-
-        /*
-         * Unregister the interrupt handler.
-         * The __ffs() function returns the index into the interrupt handler
-         * table from the interrupt bit mask which should have one bit
-         * and one bit only set.
-         */
-        if (priv->intr_id)
-                free_irq(__ffs(priv->intr_id), dev);
-
-        /*
-         * Drain all the LIPP buffers.
-         */
+        int n = 0;
 
+        /* Drain all the LIPP buffers. */
         while (true) {
                 int buffer;
 
@@ -1560,43 +1564,105 @@ static int tile_net_stop(struct net_device *dev)
 
                         kfree_skb(skb);
                 }
+
+                n++;
         }
 
-        /* Stop LIPP/LEPP. */
-        tile_net_stop_aux(dev);
+        return n;
+}
 
 
-        priv->fully_opened = 0;
+/*
+ * Disables a network interface.
+ *
+ * Returns 0, this is not allowed to fail.
+ *
+ * The close entry point is called when an interface is de-activated
+ * by the OS.  The hardware is still under the drivers control, but
+ * needs to be disabled.  A global MAC reset is issued to stop the
+ * hardware, and all transmit and receive resources are freed.
+ *
+ * ISSUE: How closely does "netif_running(dev)" mirror "priv->active"?
+ *
+ * Before we are called by "__dev_close()", "netif_running()" will
+ * have been cleared, so no NEW calls to "tile_net_poll()" will be
+ * made by "netpoll_poll_dev()".
+ *
+ * Often, this can cause some tiles to still have packets in their
+ * queues, so we must call "tile_net_discard_packets()" later.
+ *
+ * Note that some other tile may still be INSIDE "tile_net_poll()",
+ * and in fact, many will be, if there is heavy network load.
+ *
+ * Calling "on_each_cpu(tile_net_stop_disable, (void *)dev, 1)" when
+ * any tile is still "napi_schedule()"'d will induce a horrible crash
+ * when "msleep()" is called.  This includes tiles which are inside
+ * "tile_net_poll()" which have not yet called "napi_complete()".
+ *
+ * So, we must first try to wait long enough for other tiles to finish
+ * with any current "tile_net_poll()" call, and, hopefully, to clear
+ * the "scheduled" flag.  ISSUE: It is unclear what happens to tiles
+ * which have called "napi_schedule()" but which had not yet tried to
+ * call "tile_net_poll()", or which exhausted their budget inside
+ * "tile_net_poll()" just before this function was called.
+ */
+static int tile_net_stop(struct net_device *dev)
+{
+        struct tile_net_priv *priv = netdev_priv(dev);
+
+        PDEBUG("tile_net_stop()\n");
 
+        /* Start discarding packets. */
+        priv->active = false;
+
+        /* Make sure "active" is visible to all tiles. */
+        mb();
 
         /*
-         * XXX: ISSUE: It appears that, in practice anyway, by the
-         * time we get here, there are no pending completions.
+         * On each tile, make sure no NEW packets get delivered, and
+         * disable the ingress interrupt.
+         *
+         * Note that the ingress interrupt can fire AFTER this,
+         * presumably due to packets which were recently delivered,
+         * but it will have no effect.
          */
-        while (pending) {
+        on_each_cpu(tile_net_deregister, (void *)dev, 1);
 
-                struct sk_buff *olds[32];
-                unsigned int wanted = 32;
-                unsigned int i, nolds = 0;
+        /* Optimistically drain LIPP buffers. */
+        (void)tile_net_drain_lipp_buffers(priv);
 
-                nolds = tile_net_lepp_grab_comps(dev, olds,
-                                                 wanted, &pending);
+        /* ISSUE: Only needed if not yet fully open. */
+        cancel_delayed_work_sync(&priv->retry_work);
 
-                /* ISSUE: We have never actually seen this debug spew. */
-                if (nolds != 0)
-                        pr_info("During tile_net_stop(), grabbed %d comps.\n",
-                               nolds);
+        /* Can't transmit any more. */
+        netif_stop_queue(dev);
 
-                for (i = 0; i < nolds; i++)
-                        kfree_skb(olds[i]);
-        }
+        /* Disable NAPI on each tile. */
+        on_each_cpu(tile_net_stop_disable, (void *)dev, 1);
+
+        /*
+         * Drain any remaining LIPP buffers.  NOTE: This "printk()"
+         * has never been observed, but in theory it could happen.
+         */
+        if (tile_net_drain_lipp_buffers(priv) != 0)
+                printk("Had to drain some extra LIPP buffers!\n");
 
+        /* Stop LIPP/LEPP. */
+        tile_net_stop_aux(dev);
+
+        /*
+         * ISSUE: It appears that, in practice anyway, by the time we
+         * get here, there are no pending completions, but just in case,
+         * we free (all of) them anyway.
+         */
+        while (tile_net_lepp_free_comps(dev, true))
+                /* loop */;
 
         /* Wipe the EPP queue. */
-        memset(priv->epp_queue, 0, sizeof(lepp_queue_t));
+        memset(priv->eq, 0, sizeof(lepp_queue_t));
 
         /* Evict the EPP queue. */
-        finv_buffer(priv->epp_queue, PAGE_SIZE);
+        finv_buffer(priv->eq, EQ_SIZE);
 
         return 0;
 }
@@ -1742,17 +1808,15 @@ static int tile_net_tx_tso(struct sk_buff *skb, struct net_device *dev)
 
         unsigned long irqflags;
 
-        lepp_queue_t *eq = priv->epp_queue;
+        lepp_queue_t *eq = priv->eq;
 
-        struct sk_buff *olds[4];
-        unsigned int wanted = 4;
+        struct sk_buff *olds[8];
+        unsigned int wanted = 8;
         unsigned int i, nolds = 0;
 
         unsigned int cmd_head, cmd_tail, cmd_next;
         unsigned int comp_tail;
 
-        unsigned int free_slots;
-
 
         /* Paranoia. */
         BUG_ON(skb->protocol != htons(ETH_P_IP));
@@ -1780,34 +1844,32 @@ static int tile_net_tx_tso(struct sk_buff *skb, struct net_device *dev)
 
         /* Enqueue the command. */
 
-        spin_lock_irqsave(&priv->cmd_lock, irqflags);
+        spin_lock_irqsave(&priv->eq_lock, irqflags);
 
         /*
          * Handle completions if needed to make room.
          * HACK: Spin until there is sufficient room.
          */
-        free_slots = lepp_num_free_comp_slots(eq);
-        if (free_slots < 1) {
-spin:
-                nolds += tile_net_lepp_grab_comps(dev, olds + nolds,
-                                                  wanted - nolds, NULL);
-                if (lepp_num_free_comp_slots(eq) < 1)
-                        goto spin;
+        if (lepp_num_free_comp_slots(eq) == 0) {
+                nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 0);
+                if (nolds == 0) {
+busy:
+                        spin_unlock_irqrestore(&priv->eq_lock, irqflags);
+                        return NETDEV_TX_BUSY;
+                }
         }
 
         cmd_head = eq->cmd_head;
         cmd_tail = eq->cmd_tail;
 
-        /* NOTE: The "gotos" below are untested. */
-
         /* Prepare to advance, detecting full queue. */
         cmd_next = cmd_tail + cmd_size;
         if (cmd_tail < cmd_head && cmd_next >= cmd_head)
-                goto spin;
+                goto busy;
         if (cmd_next > LEPP_CMD_LIMIT) {
                 cmd_next = 0;
                 if (cmd_next == cmd_head)
-                        goto spin;
+                        goto busy;
         }
 
         /* Copy the command. */
@@ -1823,14 +1885,18 @@ spin:
         eq->comp_tail = comp_tail;
 
         /* Flush before allowing LEPP to handle the command. */
+        /* ISSUE: Is this the optimal location for the flush? */
         __insn_mf();
 
         eq->cmd_tail = cmd_tail;
 
-        spin_unlock_irqrestore(&priv->cmd_lock, irqflags);
-
+        /* NOTE: Using "4" here is more efficient than "0" or "2", */
+        /* and, strangely, more efficient than pre-checking the number */
+        /* of available completions, and comparing it to 4. */
         if (nolds == 0)
-                nolds = tile_net_lepp_grab_comps(dev, olds, wanted, NULL);
+                nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 4);
+
+        spin_unlock_irqrestore(&priv->eq_lock, irqflags);
 
         /* Handle completions. */
         for (i = 0; i < nolds; i++)
@@ -1870,10 +1936,10 @@ static int tile_net_tx(struct sk_buff *skb, struct net_device *dev)
 
         unsigned int num_frags;
 
-        lepp_queue_t *eq = priv->epp_queue;
+        lepp_queue_t *eq = priv->eq;
 
-        struct sk_buff *olds[4];
-        unsigned int wanted = 4;
+        struct sk_buff *olds[8];
+        unsigned int wanted = 8;
         unsigned int i, nolds = 0;
 
         unsigned int cmd_size = sizeof(lepp_cmd_t);
@@ -1883,8 +1949,6 @@ static int tile_net_tx(struct sk_buff *skb, struct net_device *dev)
 
         lepp_cmd_t cmds[LEPP_MAX_FRAGS];
 
-        unsigned int free_slots;
-
 
         /*
          * This is paranoia, since we think that if the link doesn't come
@@ -1905,7 +1969,8 @@ static int tile_net_tx(struct sk_buff *skb, struct net_device *dev)
         if (hash_default) {
                 HV_PTE pte = *virt_to_pte(current->mm, (unsigned long)data);
                 if (hv_pte_get_mode(pte) != HV_PTE_MODE_CACHE_HASH_L3)
-                        panic("Non-coherent egress buffer!");
+                        panic("Non-HFH egress buffer! VA=%p Mode=%d PTE=%llx",
+                              data, hv_pte_get_mode(pte), hv_pte_val(pte));
         }
 #endif
 #endif
@@ -1958,37 +2023,35 @@ static int tile_net_tx(struct sk_buff *skb, struct net_device *dev)
 
         /* Enqueue the commands. */
 
-        spin_lock_irqsave(&priv->cmd_lock, irqflags);
+        spin_lock_irqsave(&priv->eq_lock, irqflags);
 
         /*
          * Handle completions if needed to make room.
          * HACK: Spin until there is sufficient room.
          */
-        free_slots = lepp_num_free_comp_slots(eq);
-        if (free_slots < 1) {
-spin:
-                nolds += tile_net_lepp_grab_comps(dev, olds + nolds,
-                                                  wanted - nolds, NULL);
-                if (lepp_num_free_comp_slots(eq) < 1)
-                        goto spin;
+        if (lepp_num_free_comp_slots(eq) == 0) {
+                nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 0);
+                if (nolds == 0) {
+busy:
+                        spin_unlock_irqrestore(&priv->eq_lock, irqflags);
+                        return NETDEV_TX_BUSY;
+                }
         }
 
         cmd_head = eq->cmd_head;
         cmd_tail = eq->cmd_tail;
 
-        /* NOTE: The "gotos" below are untested. */
-
         /* Copy the commands, or fail. */
         for (i = 0; i < num_frags; i++) {
 
                 /* Prepare to advance, detecting full queue. */
                 cmd_next = cmd_tail + cmd_size;
                 if (cmd_tail < cmd_head && cmd_next >= cmd_head)
-                        goto spin;
+                        goto busy;
                 if (cmd_next > LEPP_CMD_LIMIT) {
                         cmd_next = 0;
                         if (cmd_next == cmd_head)
-                                goto spin;
+                                goto busy;
                 }
 
                 /* Copy the command. */
@@ -2005,14 +2068,18 @@ spin:
         eq->comp_tail = comp_tail;
 
         /* Flush before allowing LEPP to handle the command. */
+        /* ISSUE: Is this the optimal location for the flush? */
         __insn_mf();
 
         eq->cmd_tail = cmd_tail;
 
-        spin_unlock_irqrestore(&priv->cmd_lock, irqflags);
-
+        /* NOTE: Using "4" here is more efficient than "0" or "2", */
+        /* and, strangely, more efficient than pre-checking the number */
+        /* of available completions, and comparing it to 4. */
         if (nolds == 0)
-                nolds = tile_net_lepp_grab_comps(dev, olds, wanted, NULL);
+                nolds = tile_net_lepp_grab_comps(eq, olds, wanted, 4);
+
+        spin_unlock_irqrestore(&priv->eq_lock, irqflags);
 
         /* Handle completions. */
         for (i = 0; i < nolds; i++)
@@ -2261,7 +2328,6 @@ static struct net_device *tile_net_dev_init(const char *name)
         int ret;
         struct net_device *dev;
         struct tile_net_priv *priv;
-        struct page *page;
 
         /*
          * Allocate the device structure.  This allocates "priv", calls
@@ -2285,23 +2351,21 @@ static struct net_device *tile_net_dev_init(const char *name)
 
         INIT_DELAYED_WORK(&priv->retry_work, tile_net_open_retry);
 
-        spin_lock_init(&priv->cmd_lock);
-        spin_lock_init(&priv->comp_lock);
+        spin_lock_init(&priv->eq_lock);
 
-        /* Allocate "epp_queue". */
-        BUG_ON(get_order(sizeof(lepp_queue_t)) != 0);
-        page = alloc_pages(GFP_KERNEL | __GFP_ZERO, 0);
-        if (!page) {
+        /* Allocate "eq". */
+        priv->eq_pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, EQ_ORDER);
+        if (!priv->eq_pages) {
                 free_netdev(dev);
                 return NULL;
         }
-        priv->epp_queue = page_address(page);
+        priv->eq = page_address(priv->eq_pages);
 
         /* Register the network device. */
         ret = register_netdev(dev);
         if (ret) {
                 pr_err("register_netdev %s failed %d\n", dev->name, ret);
-                free_page((unsigned long)priv->epp_queue);
+                __free_pages(priv->eq_pages, EQ_ORDER);
                 free_netdev(dev);
                 return NULL;
         }
@@ -2310,7 +2374,7 @@ static struct net_device *tile_net_dev_init(const char *name)
         ret = tile_net_get_mac(dev);
         if (ret < 0) {
                 unregister_netdev(dev);
-                free_page((unsigned long)priv->epp_queue);
+                __free_pages(priv->eq_pages, EQ_ORDER);
                 free_netdev(dev);
                 return NULL;
         }
@@ -2321,6 +2385,9 @@ static struct net_device *tile_net_dev_init(const char *name)
 
 /*
  * Module cleanup.
+ *
+ * FIXME: If compiled as a module, this module cannot be "unloaded",
+ * because the "ingress interrupt handler" is registered permanently.
  */
 static void tile_net_cleanup(void)
 {
@@ -2331,8 +2398,8 @@ static void tile_net_cleanup(void)
                         struct net_device *dev = tile_net_devs[i];
                         struct tile_net_priv *priv = netdev_priv(dev);
                         unregister_netdev(dev);
-                        finv_buffer(priv->epp_queue, PAGE_SIZE);
-                        free_page((unsigned long)priv->epp_queue);
+                        finv_buffer(priv->eq, EQ_SIZE);
+                        __free_pages(priv->eq_pages, EQ_ORDER);
                         free_netdev(dev);
                 }
         }
@@ -2355,7 +2422,12 @@ static int tile_net_init_module(void)
 }
 
 
+module_init(tile_net_init_module);
+module_exit(tile_net_cleanup);
+
+
 #ifndef MODULE
+
 /*
  * The "network_cpus" boot argument specifies the cpus that are dedicated
  * to handle ingress packets.
@@ -2391,8 +2463,5 @@ static int __init network_cpus_setup(char *str)
         return 0;
 }
 __setup("network_cpus=", network_cpus_setup);
-#endif
-
 
-module_init(tile_net_init_module);
-module_exit(tile_net_cleanup);
+#endif