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firewire: net: replace lists by counters

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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 <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Stefan Richter 2010-11-06 23:18:23 +01:00
parent 7ee11fa8d0
commit 48553011ce
1 changed files with 26 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

73
drivers/firewire/net.c
View File

@ -7,6 +7,7 @@
*/
#include <linux/bug.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/firewire.h>
#include <linux/firewire-constants.h>
@ -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(struct fwnet_packet_task *ptask)
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(struct fwnet_packet_task *ptask)
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 fwnet_packet_task *ptask)
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 fwnet_packet_task *ptask)
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_buff *skb, struct net_device *net)
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 *_dev)
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 *_dev)
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)
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);