Date: Sat, 6 Nov 2010 23:18:23 +0100 (CET) From: Stefan Richter Subject: firewire: net: replace lists by counters The current transmit code does not at all make use of - fwnet_device.packet_list and only very limited use of - fwnet_device.broadcasted_list, - fwnet_device.queued_packets. Their current function is to track whether the TX soft-IRQ finished dealing with an skb when the AT-req tasklet takes over, and to discard pending tx datagrams (if there are any) when the local node is removed. The latter does actually contain a race condition bug with TX soft-IRQ and AT-req tasklet. Instead of these lists and the corresponding link in fwnet_packet_task, - a flag in fwnet_packet_task to track whether fwnet_tx is done, - a counter of queued datagrams in fwnet_device do the job as well. The above mentioned theoretic race condition is resolved by letting fwnet_remove sleep until all datagrams were flushed. It may sleep almost arbitrarily long since fwnet_remove is executed in the context of a multithreaded (concurrency managed) workqueue. The type of max_payload is changed to u16 here to avoid waste in struct fwnet_packet_task. This value cannot exceed 4096 per IEEE 1394:2008 table 16-18 (or 32678 per specification of packet headers, if there is ever going to be something else than beta mode). Signed-off-by: Stefan Richter --- drivers/firewire/net.c | 73 +++++++++++++++-------------------------- 1 file changed, 26 insertions(+), 47 deletions(-) Index: b/drivers/firewire/net.c =================================================================== --- a/drivers/firewire/net.c +++ b/drivers/firewire/net.c @@ -7,6 +7,7 @@ */ #include +#include #include #include #include @@ -169,15 +170,8 @@ struct fwnet_device { struct fw_address_handler handler; u64 local_fifo; - /* List of packets to be sent */ - struct list_head packet_list; - /* - * List of packets that were broadcasted. When we get an ISO interrupt - * one of them has been sent - */ - struct list_head broadcasted_list; - /* List of packets that have been sent but not yet acked */ - struct list_head sent_list; + /* Number of tx datagrams that have been queued but not yet acked */ + int queued_datagrams; struct list_head peer_list; struct fw_card *card; @@ -195,7 +189,7 @@ struct fwnet_peer { unsigned pdg_size; /* pd_list size */ u16 datagram_label; /* outgoing datagram label */ - unsigned max_payload; /* includes RFC2374_FRAG_HDR_SIZE overhead */ + u16 max_payload; /* includes RFC2374_FRAG_HDR_SIZE overhead */ int node_id; int generation; unsigned speed; @@ -203,22 +197,18 @@ struct fwnet_peer { /* This is our task struct. It's used for the packet complete callback. */ struct fwnet_packet_task { - /* - * ptask can actually be on dev->packet_list, dev->broadcasted_list, - * or dev->sent_list depending on its current state. - */ - struct list_head pt_link; struct fw_transaction transaction; struct rfc2734_header hdr; struct sk_buff *skb; struct fwnet_device *dev; int outstanding_pkts; - unsigned max_payload; u64 fifo_addr; u16 dest_node; + u16 max_payload; u8 generation; u8 speed; + u8 enqueued; }; /* @@ -915,9 +905,9 @@ static void fwnet_transmit_packet_done(s ptask->outstanding_pkts--; /* Check whether we or the networking TX soft-IRQ is last user. */ - free = (ptask->outstanding_pkts == 0 && !list_empty(&ptask->pt_link)); + free = (ptask->outstanding_pkts == 0 && ptask->enqueued); if (free) - list_del(&ptask->pt_link); + dev->queued_datagrams--; if (ptask->outstanding_pkts == 0) { dev->netdev->stats.tx_packets++; @@ -986,9 +976,9 @@ static void fwnet_transmit_packet_failed ptask->outstanding_pkts = 0; /* Check whether we or the networking TX soft-IRQ is last user. */ - free = !list_empty(&ptask->pt_link); + free = ptask->enqueued; if (free) - list_del(&ptask->pt_link); + dev->queued_datagrams--; dev->netdev->stats.tx_dropped++; dev->netdev->stats.tx_errors++; @@ -1069,9 +1059,11 @@ static int fwnet_send_packet(struct fwne spin_lock_irqsave(&dev->lock, flags); /* If the AT tasklet already ran, we may be last user. */ - free = (ptask->outstanding_pkts == 0 && list_empty(&ptask->pt_link)); + free = (ptask->outstanding_pkts == 0 && !ptask->enqueued); if (!free) - list_add_tail(&ptask->pt_link, &dev->broadcasted_list); + ptask->enqueued = true; + else + dev->queued_datagrams--; spin_unlock_irqrestore(&dev->lock, flags); @@ -1086,9 +1078,11 @@ static int fwnet_send_packet(struct fwne spin_lock_irqsave(&dev->lock, flags); /* If the AT tasklet already ran, we may be last user. */ - free = (ptask->outstanding_pkts == 0 && list_empty(&ptask->pt_link)); + free = (ptask->outstanding_pkts == 0 && !ptask->enqueued); if (!free) - list_add_tail(&ptask->pt_link, &dev->sent_list); + ptask->enqueued = true; + else + dev->queued_datagrams--; spin_unlock_irqrestore(&dev->lock, flags); @@ -1350,10 +1344,12 @@ static netdev_tx_t fwnet_tx(struct sk_bu max_payload += RFC2374_FRAG_HDR_SIZE; } + dev->queued_datagrams++; + spin_unlock_irqrestore(&dev->lock, flags); ptask->max_payload = max_payload; - INIT_LIST_HEAD(&ptask->pt_link); + ptask->enqueued = 0; fwnet_send_packet(ptask); @@ -1487,14 +1483,9 @@ static int fwnet_probe(struct device *_d dev->broadcast_rcv_context = NULL; dev->broadcast_xmt_max_payload = 0; dev->broadcast_xmt_datagramlabel = 0; - dev->local_fifo = FWNET_NO_FIFO_ADDR; - - INIT_LIST_HEAD(&dev->packet_list); - INIT_LIST_HEAD(&dev->broadcasted_list); - INIT_LIST_HEAD(&dev->sent_list); + dev->queued_datagrams = 0; INIT_LIST_HEAD(&dev->peer_list); - dev->card = card; dev->netdev = net; @@ -1552,7 +1543,7 @@ static int fwnet_remove(struct device *_ struct fwnet_peer *peer = dev_get_drvdata(_dev); struct fwnet_device *dev = peer->dev; struct net_device *net; - struct fwnet_packet_task *ptask, *pt_next; + int i; mutex_lock(&fwnet_device_mutex); @@ -1570,21 +1561,9 @@ static int fwnet_remove(struct device *_ dev->card); fw_iso_context_destroy(dev->broadcast_rcv_context); } - list_for_each_entry_safe(ptask, pt_next, - &dev->packet_list, pt_link) { - dev_kfree_skb_any(ptask->skb); - kmem_cache_free(fwnet_packet_task_cache, ptask); - } - list_for_each_entry_safe(ptask, pt_next, - &dev->broadcasted_list, pt_link) { - dev_kfree_skb_any(ptask->skb); - kmem_cache_free(fwnet_packet_task_cache, ptask); - } - list_for_each_entry_safe(ptask, pt_next, - &dev->sent_list, pt_link) { - dev_kfree_skb_any(ptask->skb); - kmem_cache_free(fwnet_packet_task_cache, ptask); - } + for (i = 0; dev->queued_datagrams && i < 5; i++) + ssleep(1); + WARN_ON(dev->queued_datagrams); list_del(&dev->dev_link); free_netdev(net);