diff options
| author | Eric Dumazet <edumazet@google.com> | 2015-11-18 06:30:50 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-11-18 16:17:37 -0500 |
| commit | 52bd2d62ce6758d811edcbd2256eb9ea7f6a56cb (patch) | |
| tree | a05cc3913f4389700efef15cccf882befbcd6d32 /net/core | |
| parent | d37b4c0a3647db23f41c5ee85701eec3544446d1 (diff) | |
net: better skb->sender_cpu and skb->napi_id cohabitation
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@google.com>
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/dev.c | 33 |
1 files changed, 16 insertions, 17 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index ae00b894e675..2582c24a75c6 100644 --- 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; @@ -3021,7 +3021,9 @@ struct netdev_queue *netdev_pick_tx(struct net_device *dev, 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 @@ -4676,25 +4678,22 @@ 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); |