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Message-ID: <alpine.DEB.1.00.1005202101290.25742@pokey.mtv.corp.google.com>
Date: Thu, 20 May 2010 21:37:59 -0700 (PDT)
From: Tom Herbert <therbert@...gle.com>
To: davem@...emloft.net
cc: eric.dumazet@...il.com, xiaosuo@...il.com, netdev@...r.kernel.org
Subject: [PATCH v2] 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 <therbert@...gle.com>
---
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index c3487a6..726b3cb 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1403,17 +1403,25 @@ 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 6c82065..0aab66d 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;
}
--
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