Commit 4d092dd2 authored by Jakub Kicinski's avatar Jakub Kicinski Committed by David S. Miller
Browse files

net: manage napi add/del idempotence explicitly 



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: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5198d545

include/linux/netdevice.h

+2 −2
Original line number Diff line number Diff line
@@ -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),

};

net/core/dev.c

+9 −4
Original line number Diff line number Diff line
@@ -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);