From 76cc8b13a6e41b537fd262b600da1571314add62 Mon Sep 17 00:00:00 2001 From: Tom Herbert Date: Thu, 20 May 2010 18:37:59 +0000 Subject: [PATCH] net: fix problem in dequeuing from input_pkt_queue 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 Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/netdevice.h | 14 +++++++++++--- net/core/dev.c | 28 +++++++++++++++------------- 2 files changed, 26 insertions(+), 16 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index a1bff6518166..256419583d9d 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -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 } diff --git a/net/core/dev.c b/net/core/dev.c index 6c820650b80f..0aab66d68b19 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2426,10 +2426,7 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu, if (skb_queue_len(&sd->input_pkt_queue)) { enqueue: __skb_queue_tail(&sd->input_pkt_queue, skb); -#ifdef CONFIG_RPS - *qtail = sd->input_queue_head + - skb_queue_len(&sd->input_pkt_queue); -#endif + input_queue_tail_incr_save(sd, qtail); rps_unlock(sd); local_irq_restore(flags); return NET_RX_SUCCESS; @@ -2964,7 +2961,7 @@ static void flush_backlog(void *arg) if (skb->dev == dev) { __skb_unlink(skb, &sd->input_pkt_queue); kfree_skb(skb); - input_queue_head_add(sd, 1); + input_queue_head_incr(sd); } } rps_unlock(sd); @@ -2973,6 +2970,7 @@ static void flush_backlog(void *arg) if (skb->dev == dev) { __skb_unlink(skb, &sd->process_queue); kfree_skb(skb); + input_queue_head_incr(sd); } } } @@ -3328,18 +3326,20 @@ static int process_backlog(struct napi_struct *napi, int quota) while ((skb = __skb_dequeue(&sd->process_queue))) { local_irq_enable(); __netif_receive_skb(skb); - if (++work >= quota) - return work; local_irq_disable(); + input_queue_head_incr(sd); + if (++work >= quota) { + local_irq_enable(); + return work; + } } rps_lock(sd); qlen = skb_queue_len(&sd->input_pkt_queue); - if (qlen) { - input_queue_head_add(sd, qlen); + if (qlen) skb_queue_splice_tail_init(&sd->input_pkt_queue, &sd->process_queue); - } + if (qlen < quota - work) { /* * Inline a custom version of __napi_complete(). @@ -5679,12 +5679,14 @@ static int dev_cpu_callback(struct notifier_block *nfb, local_irq_enable(); /* Process offline CPU's input_pkt_queue */ - while ((skb = __skb_dequeue(&oldsd->input_pkt_queue))) { + while ((skb = __skb_dequeue(&oldsd->process_queue))) { netif_rx(skb); - input_queue_head_add(oldsd, 1); + input_queue_head_incr(oldsd); } - while ((skb = __skb_dequeue(&oldsd->process_queue))) + while ((skb = __skb_dequeue(&oldsd->input_pkt_queue))) { netif_rx(skb); + input_queue_head_incr(oldsd); + } return NOTIFY_OK; } -- 2.34.1