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Commit 545cd5e5 authored by Alexander Duyck's avatar Alexander Duyck Committed by David S. Miller
Browse files

net: Busy polling should ignore sender CPUs 



This patch is a cleanup/fix for NAPI IDs following the changes that made it
so that sender_cpu and napi_id were doing a better job of sharing the same
location in the sk_buff.

One issue I found is that we weren't validating the napi_id as being valid
before we started trying to setup the busy polling.  This change corrects
that by using the MIN_NAPI_ID value that is now used in both allocating the
NAPI IDs, as well as validating them.

Signed-off-by: default avatarAlexander Duyck <alexander.h.duyck@intel.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent dcb421f4

include/net/busy_poll.h

+7 −2
Original line number Diff line number Diff line
@@ -35,6 +35,12 @@ struct napi_struct; 
extern unsigned int sysctl_net_busy_read __read_mostly;

extern unsigned int sysctl_net_busy_poll __read_mostly;



/*		0 - Reserved to indicate value not set

 *     1..NR_CPUS - Reserved for sender_cpu

 *  NR_CPUS+1..~0 - Region available for NAPI IDs

 */

#define MIN_NAPI_ID ((unsigned int)(NR_CPUS + 1))



static inline bool net_busy_loop_on(void)

{

	return sysctl_net_busy_poll;
@@ -58,10 +64,9 @@ static inline unsigned long busy_loop_end_time(void) 


static inline bool sk_can_busy_loop(const struct sock *sk)

{

	return sk->sk_ll_usec && sk->sk_napi_id && !signal_pending(current);

	return sk->sk_ll_usec && !signal_pending(current);

}





static inline bool busy_loop_timeout(unsigned long end_time)

{

	unsigned long now = busy_loop_us_clock();

net/core/dev.c

+9 −4
Original line number Diff line number Diff line
@@ -5066,15 +5066,20 @@ bool sk_busy_loop(struct sock *sk, int nonblock) 
	int (*napi_poll)(struct napi_struct *napi, int budget);

	void *have_poll_lock = NULL;

	struct napi_struct *napi;

	unsigned int napi_id;

	int rc;



restart:

	napi_id = READ_ONCE(sk->sk_napi_id);

	if (napi_id < MIN_NAPI_ID)

		return 0;



	rc = false;

	napi_poll = NULL;



	rcu_read_lock();



	napi = napi_by_id(sk->sk_napi_id);

	napi = napi_by_id(napi_id);

	if (!napi)

		goto out;
@@ -5143,10 +5148,10 @@ static void napi_hash_add(struct napi_struct *napi) 


	spin_lock(&napi_hash_lock);



	/* 0..NR_CPUS+1 range is reserved for sender_cpu use */

	/* 0..NR_CPUS range is reserved for sender_cpu use */

	do {

		if (unlikely(++napi_gen_id < NR_CPUS + 1))

			napi_gen_id = NR_CPUS + 1;

		if (unlikely(++napi_gen_id < MIN_NAPI_ID))

			napi_gen_id = MIN_NAPI_ID;

	} while (napi_by_id(napi_gen_id));

	napi->napi_id = napi_gen_id;