This is a note to let you know that I've just added the patch titled
net: better skb->sender_cpu and skb->napi_id cohabitation
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-better-skb-sender_cpu-and-skb-napi_id-cohabitation.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 52bd2d62ce6758d811edcbd2256eb9ea7f6a56cb Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Wed, 18 Nov 2015 06:30:50 -0800
Subject: net: better skb->sender_cpu and skb->napi_id cohabitation
From: Eric Dumazet <edumazet@xxxxxxxxxx>
commit 52bd2d62ce6758d811edcbd2256eb9ea7f6a56cb upstream.
skb->sender_cpu and skb->napi_id share a common storage,
and we had various bugs about this.
We had to call skb_sender_cpu_clear() in some places to
not leave a prior skb->napi_id and fool netdev_pick_tx()
As suggested by Alexei, we could split the space so that
these errors can not happen.
0 value being reserved as the common (not initialized) value,
let's reserve [1 .. NR_CPUS] range for valid sender_cpu,
and [NR_CPUS+1 .. ~0U] for valid napi_id.
This will allow proper busy polling support over tunnels.
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Suggested-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Paul Menzel <pmenzel@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/skbuff.h | 3 ---
net/core/dev.c | 33 ++++++++++++++++-----------------
2 files changed, 16 insertions(+), 20 deletions(-)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1084,9 +1084,6 @@ static inline void skb_copy_hash(struct
static inline void skb_sender_cpu_clear(struct sk_buff *skb)
{
-#ifdef CONFIG_XPS
- skb->sender_cpu = 0;
-#endif
}
#ifdef NET_SKBUFF_DATA_USES_OFFSET
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -182,7 +182,7 @@ EXPORT_SYMBOL(dev_base_lock);
/* protects napi_hash addition/deletion and napi_gen_id */
static DEFINE_SPINLOCK(napi_hash_lock);
-static unsigned int napi_gen_id;
+static unsigned int napi_gen_id = NR_CPUS;
static DEFINE_HASHTABLE(napi_hash, 8);
static seqcount_t devnet_rename_seq;
@@ -3049,7 +3049,9 @@ struct netdev_queue *netdev_pick_tx(stru
int queue_index = 0;
#ifdef CONFIG_XPS
- if (skb->sender_cpu == 0)
+ u32 sender_cpu = skb->sender_cpu - 1;
+
+ if (sender_cpu >= (u32)NR_CPUS)
skb->sender_cpu = raw_smp_processor_id() + 1;
#endif
@@ -4726,25 +4728,22 @@ EXPORT_SYMBOL_GPL(napi_by_id);
void napi_hash_add(struct napi_struct *napi)
{
- if (!test_and_set_bit(NAPI_STATE_HASHED, &napi->state)) {
+ if (test_and_set_bit(NAPI_STATE_HASHED, &napi->state))
+ return;
- spin_lock(&napi_hash_lock);
+ spin_lock(&napi_hash_lock);
- /* 0 is not a valid id, we also skip an id that is taken
- * we expect both events to be extremely rare
- */
- napi->napi_id = 0;
- while (!napi->napi_id) {
- napi->napi_id = ++napi_gen_id;
- if (napi_by_id(napi->napi_id))
- napi->napi_id = 0;
- }
+ /* 0..NR_CPUS+1 range is reserved for sender_cpu use */
+ do {
+ if (unlikely(++napi_gen_id < NR_CPUS + 1))
+ napi_gen_id = NR_CPUS + 1;
+ } while (napi_by_id(napi_gen_id));
+ napi->napi_id = napi_gen_id;
- hlist_add_head_rcu(&napi->napi_hash_node,
- &napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
+ hlist_add_head_rcu(&napi->napi_hash_node,
+ &napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
- spin_unlock(&napi_hash_lock);
- }
+ spin_unlock(&napi_hash_lock);
}
EXPORT_SYMBOL_GPL(napi_hash_add);
Patches currently in stable-queue which might be from edumazet@xxxxxxxxxx are
queue-4.4/tcp-disallow-cwnd-undo-when-switching-congestion-control.patch
queue-4.4/net-better-skb-sender_cpu-and-skb-napi_id-cohabitation.patch
queue-4.4/net-ping-do-not-abuse-udp_poll.patch