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net: manage napi add/del idempotence explicitly

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To RCUify napi->dev_list we need to replace list_del_init()
with list_del_rcu(). There is no _init() version for RCU for
obvious reasons. Up until now netif_napi_del() was idempotent
so to make sure it remains such add a bit which is set when
NAPI is listed, and cleared when it removed. Since we don't
expect multiple calls to netif_napi_add() to be correct,
add a warning on that side.

Now that napi_hash_add / napi_hash_del are only called by
napi_add / del we can actually steal its bit. We just need
to make sure hash node is initialized correctly.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jakub Kicinski 2020-09-09 10:37:52 -07:00 committed by David S. Miller
parent 5198d545db
commit 4d092dd204
2 changed files with 11 additions and 6 deletions
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4
include/linux/netdevice.h
View file

@ -355,7 +355,7 @@ enum {
NAPI_STATE_MISSED, /* reschedule a napi */
NAPI_STATE_DISABLE, /* Disable pending */
NAPI_STATE_NPSVC, /* Netpoll - don't dequeue from poll_list */
NAPI_STATE_HASHED, /* In NAPI hash (busy polling possible) */
NAPI_STATE_LISTED, /* NAPI added to system lists */
NAPI_STATE_NO_BUSY_POLL,/* Do not add in napi_hash, no busy polling */
NAPI_STATE_IN_BUSY_POLL,/* sk_busy_loop() owns this NAPI */
};
@ -365,7 +365,7 @@ enum {
NAPIF_STATE_MISSED = BIT(NAPI_STATE_MISSED),
NAPIF_STATE_DISABLE = BIT(NAPI_STATE_DISABLE),
NAPIF_STATE_NPSVC = BIT(NAPI_STATE_NPSVC),
NAPIF_STATE_HASHED = BIT(NAPI_STATE_HASHED),
NAPIF_STATE_LISTED = BIT(NAPI_STATE_LISTED),
NAPIF_STATE_NO_BUSY_POLL = BIT(NAPI_STATE_NO_BUSY_POLL),
NAPIF_STATE_IN_BUSY_POLL = BIT(NAPI_STATE_IN_BUSY_POLL),
};

13
net/core/dev.c
View file

@ -6533,8 +6533,7 @@ EXPORT_SYMBOL(napi_busy_loop);
static void napi_hash_add(struct napi_struct *napi)
{
if (test_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state) ||
test_and_set_bit(NAPI_STATE_HASHED, &napi->state))
if (test_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state))
return;
spin_lock(&napi_hash_lock);
@ -6559,8 +6558,7 @@ static void napi_hash_del(struct napi_struct *napi)
{
spin_lock(&napi_hash_lock);
if (test_and_clear_bit(NAPI_STATE_HASHED, &napi->state))
hlist_del_rcu(&napi->napi_hash_node);
hlist_del_init_rcu(&napi->napi_hash_node);
spin_unlock(&napi_hash_lock);
}
@ -6595,7 +6593,11 @@ static void init_gro_hash(struct napi_struct *napi)
void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
int (*poll)(struct napi_struct *, int), int weight)
{
if (WARN_ON(test_and_set_bit(NAPI_STATE_LISTED, &napi->state)))
return;
INIT_LIST_HEAD(&napi->poll_list);
INIT_HLIST_NODE(&napi->napi_hash_node);
hrtimer_init(&napi->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
napi->timer.function = napi_watchdog;
init_gro_hash(napi);
@ -6650,6 +6652,9 @@ static void flush_gro_hash(struct napi_struct *napi)
/* Must be called in process context */
void __netif_napi_del(struct napi_struct *napi)
{
if (!test_and_clear_bit(NAPI_STATE_LISTED, &napi->state))
return;
napi_hash_del(napi);
list_del_init(&napi->dev_list);
napi_free_frags(napi);