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net: fix problem in dequeuing from input_pkt_queue

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Fix some issues introduced in batch skb dequeuing for input_pkt_queue.
The primary issue it that the queue head must be incremented only
after a packet has been processed, that is only after
__netif_receive_skb has been called.  This is needed for the mechanism
to prevent OOO packet in RFS.  Also when flushing the input_pkt_queue
and process_queue, the process queue should be done first to prevent
OOO packets.

Because the input_pkt_queue has been effectively split into two queues,
the calculation of the tail ptr is no longer correct.  The correct value
would be head+input_pkt_queue->len+process_queue->len.  To avoid
this calculation we added an explict input_queue_tail in softnet_data.
The tail value is simply incremented when queuing to input_pkt_queue.

Signed-off-by: Tom Herbert <therbert@google.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Tom Herbert 2010-05-20 18:37:59 +00:00 • committed by David S. Miller
parent 1f01bfd202
commit 76cc8b13a6
2 changed files with 26 additions and 16 deletions
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14
include/linux/netdevice.h
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@ -1407,17 +1407,25 @@ struct softnet_data {
struct softnet_data *rps_ipi_next;
unsigned int cpu;
unsigned int input_queue_head;
unsigned int input_queue_tail;
#endif
unsigned dropped;
struct sk_buff_head input_pkt_queue;
struct napi_struct backlog;
};
static inline void input_queue_head_add(struct softnet_data *sd,
unsigned int len)
static inline void input_queue_head_incr(struct softnet_data *sd)
{
#ifdef CONFIG_RPS
sd->input_queue_head += len;
sd->input_queue_head++;
#endif
}
static inline void input_queue_tail_incr_save(struct softnet_data *sd,
unsigned int *qtail)
{
#ifdef CONFIG_RPS
*qtail = ++sd->input_queue_tail;
#endif
}