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Commit b2827053 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: convert syn_wait_lock to a spinlock 



This is a low hanging fruit, as we'll get rid of syn_wait_lock eventually.

We hold syn_wait_lock for such small sections, that it makes no sense to use
a read/write lock. A spin lock is simply faster.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8b929ab1

include/net/request_sock.h

+3 −8
Original line number Diff line number Diff line
@@ -173,11 +173,6 @@ struct fastopen_queue { 
 * %syn_wait_lock is necessary only to avoid proc interface having to grab the main

 * lock sock while browsing the listening hash (otherwise it's deadlock prone).

 *

 * This lock is acquired in read mode only from listening_get_next() seq_file

 * op and it's acquired in write mode _only_ from code that is actively

 * changing rskq_accept_head. All readers that are holding the master sock lock

 * don't need to grab this lock in read mode too as rskq_accept_head. writes

 * are always protected from the main sock lock.

 */

struct request_sock_queue {

	struct request_sock	*rskq_accept_head;
@@ -192,7 +187,7 @@ struct request_sock_queue { 
					     */



	/* temporary alignment, our goal is to get rid of this lock */

	rwlock_t		syn_wait_lock ____cacheline_aligned_in_smp;

	spinlock_t		syn_wait_lock ____cacheline_aligned_in_smp;

};



int reqsk_queue_alloc(struct request_sock_queue *queue,
@@ -223,14 +218,14 @@ static inline void reqsk_queue_unlink(struct request_sock_queue *queue, 
	struct listen_sock *lopt = queue->listen_opt;

	struct request_sock **prev;



	write_lock(&queue->syn_wait_lock);

	spin_lock(&queue->syn_wait_lock);



	prev = &lopt->syn_table[req->rsk_hash];

	while (*prev != req)

		prev = &(*prev)->dl_next;

	*prev = req->dl_next;



	write_unlock(&queue->syn_wait_lock);

	spin_unlock(&queue->syn_wait_lock);

	if (del_timer(&req->rsk_timer))

		reqsk_put(req);

}

net/core/request_sock.c

+7 −7
Original line number Diff line number Diff line
@@ -58,14 +58,14 @@ int reqsk_queue_alloc(struct request_sock_queue *queue, 
		return -ENOMEM;



	get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd));

	rwlock_init(&queue->syn_wait_lock);

	spin_lock_init(&queue->syn_wait_lock);

	queue->rskq_accept_head = NULL;

	lopt->nr_table_entries = nr_table_entries;

	lopt->max_qlen_log = ilog2(nr_table_entries);



	write_lock_bh(&queue->syn_wait_lock);

	spin_lock_bh(&queue->syn_wait_lock);

	queue->listen_opt = lopt;

	write_unlock_bh(&queue->syn_wait_lock);

	spin_unlock_bh(&queue->syn_wait_lock);



	return 0;

}
@@ -81,10 +81,10 @@ static inline struct listen_sock *reqsk_queue_yank_listen_sk( 
{

	struct listen_sock *lopt;



	write_lock_bh(&queue->syn_wait_lock);

	spin_lock_bh(&queue->syn_wait_lock);

	lopt = queue->listen_opt;

	queue->listen_opt = NULL;

	write_unlock_bh(&queue->syn_wait_lock);

	spin_unlock_bh(&queue->syn_wait_lock);



	return lopt;

}
@@ -100,7 +100,7 @@ void reqsk_queue_destroy(struct request_sock_queue *queue) 
		for (i = 0; i < lopt->nr_table_entries; i++) {

			struct request_sock *req;



			write_lock_bh(&queue->syn_wait_lock);

			spin_lock_bh(&queue->syn_wait_lock);

			while ((req = lopt->syn_table[i]) != NULL) {

				lopt->syn_table[i] = req->dl_next;

				atomic_inc(&lopt->qlen_dec);
@@ -108,7 +108,7 @@ void reqsk_queue_destroy(struct request_sock_queue *queue) 
					reqsk_put(req);

				reqsk_put(req);

			}

			write_unlock_bh(&queue->syn_wait_lock);

			spin_unlock_bh(&queue->syn_wait_lock);

		}

	}

net/ipv4/inet_connection_sock.c

+4 −4
Original line number Diff line number Diff line
@@ -495,7 +495,7 @@ struct request_sock *inet_csk_search_req(struct sock *sk, 
	u32 hash = inet_synq_hash(raddr, rport, lopt->hash_rnd,

				  lopt->nr_table_entries);



	write_lock(&icsk->icsk_accept_queue.syn_wait_lock);

	spin_lock(&icsk->icsk_accept_queue.syn_wait_lock);

	for (req = lopt->syn_table[hash]; req != NULL; req = req->dl_next) {

		const struct inet_request_sock *ireq = inet_rsk(req);
@@ -508,7 +508,7 @@ struct request_sock *inet_csk_search_req(struct sock *sk, 
			break;

		}

	}

	write_unlock(&icsk->icsk_accept_queue.syn_wait_lock);

	spin_unlock(&icsk->icsk_accept_queue.syn_wait_lock);



	return req;

}
@@ -650,10 +650,10 @@ void reqsk_queue_hash_req(struct request_sock_queue *queue, 
	setup_timer(&req->rsk_timer, reqsk_timer_handler, (unsigned long)req);

	req->rsk_hash = hash;



	write_lock(&queue->syn_wait_lock);

	spin_lock(&queue->syn_wait_lock);

	req->dl_next = lopt->syn_table[hash];

	lopt->syn_table[hash] = req;

	write_unlock(&queue->syn_wait_lock);

	spin_unlock(&queue->syn_wait_lock);



	mod_timer_pinned(&req->rsk_timer, jiffies + timeout);

}

net/ipv4/inet_diag.c

+2 −2
Original line number Diff line number Diff line
@@ -728,7 +728,7 @@ static int inet_diag_dump_reqs(struct sk_buff *skb, struct sock *sk, 


	entry.family = sk->sk_family;



	read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

	spin_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);



	lopt = icsk->icsk_accept_queue.listen_opt;

	if (!lopt || !listen_sock_qlen(lopt))
@@ -776,7 +776,7 @@ static int inet_diag_dump_reqs(struct sk_buff *skb, struct sock *sk, 
	}



out:

	read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

	spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);



	return err;

}

net/ipv4/tcp_ipv4.c

+6 −6
Original line number Diff line number Diff line
@@ -1909,13 +1909,13 @@ static void *listening_get_next(struct seq_file *seq, void *cur) 
		}

		sk	  = sk_nulls_next(st->syn_wait_sk);

		st->state = TCP_SEQ_STATE_LISTENING;

		read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

		spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

	} else {

		icsk = inet_csk(sk);

		read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

		spin_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

		if (reqsk_queue_len(&icsk->icsk_accept_queue))

			goto start_req;

		read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

		spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

		sk = sk_nulls_next(sk);

	}

get_sk:
@@ -1927,7 +1927,7 @@ static void *listening_get_next(struct seq_file *seq, void *cur) 
			goto out;

		}

		icsk = inet_csk(sk);

		read_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

		spin_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

		if (reqsk_queue_len(&icsk->icsk_accept_queue)) {

start_req:

			st->uid		= sock_i_uid(sk);
@@ -1936,7 +1936,7 @@ static void *listening_get_next(struct seq_file *seq, void *cur) 
			st->sbucket	= 0;

			goto get_req;

		}

		read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

		spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

	}

	spin_unlock_bh(&ilb->lock);

	st->offset = 0;
@@ -2155,7 +2155,7 @@ static void tcp_seq_stop(struct seq_file *seq, void *v) 
	case TCP_SEQ_STATE_OPENREQ:

		if (v) {

			struct inet_connection_sock *icsk = inet_csk(st->syn_wait_sk);

			read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

			spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);

		}

	case TCP_SEQ_STATE_LISTENING:

		if (v != SEQ_START_TOKEN)