path: root/net
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authorJohn Fastabend <john.r.fastabend@intel.com>2010-07-01 13:21:57 +0000
committerDavid S. Miller <davem@davemloft.net>2010-07-02 21:59:07 -0700
commitf0796d5c73e59786d09a1e617689d1d415f2db44 (patch)
treeecb17c65c5b6a162824a1e11fee24364852837f8 /net
parent4ef6acff83222f4496ceef7d1f0ee9e50a5bb403 (diff)
net: decreasing real_num_tx_queues needs to flush qdisc
Reducing real_num_queues needs to flush the qdisc otherwise skbs with queue_mappings greater then real_num_tx_queues can be sent to the underlying driver. The flow for this is, dev_queue_xmit() dev_pick_tx() skb_tx_hash() => hash using real_num_tx_queues skb_set_queue_mapping() ... qdisc_enqueue_root() => enqueue skb on txq from hash ... dev->real_num_tx_queues -= n ... sch_direct_xmit() dev_hard_start_xmit() ndo_start_xmit(skb,dev) => skb queue set with old hash skbs are enqueued on the qdisc with skb->queue_mapping set 0 < queue_mappings < real_num_tx_queues. When the driver decreases real_num_tx_queues skb's may be dequeued from the qdisc with a queue_mapping greater then real_num_tx_queues. This fixes a case in ixgbe where this was occurring with DCB and FCoE. Because the driver is using queue_mapping to map skbs to tx descriptor rings we can potentially map skbs to rings that no longer exist. Signed-off-by: John Fastabend <john.r.fastabend@intel.com> Tested-by: Ross Brattain <ross.b.brattain@intel.com> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
1 files changed, 18 insertions, 0 deletions
diff --git a/net/core/dev.c b/net/core/dev.c
index 2b3bf53bc68..723a34710ad 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1553,6 +1553,24 @@ static void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev)
+ * Routine to help set real_num_tx_queues. To avoid skbs mapped to queues
+ * greater then real_num_tx_queues stale skbs on the qdisc must be flushed.
+ */
+void netif_set_real_num_tx_queues(struct net_device *dev, unsigned int txq)
+ unsigned int real_num = dev->real_num_tx_queues;
+ if (unlikely(txq > dev->num_tx_queues))
+ ;
+ else if (txq > real_num)
+ dev->real_num_tx_queues = txq;
+ else if (txq < real_num) {
+ dev->real_num_tx_queues = txq;
+ qdisc_reset_all_tx_gt(dev, txq);
+ }
static inline void __netif_reschedule(struct Qdisc *q)