Commit 6532e257 authored by Eric Dumazet's avatar Eric Dumazet Committed by Paolo Abeni
Browse files

tcp_metrics: optimize tcp_metrics_flush_all() 



This is inspired by several syzbot reports where
tcp_metrics_flush_all() was seen in the traces.

We can avoid acquiring tcp_metrics_lock for empty buckets,
and we should add one cond_resched() to break potential long loops.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarDavid Ahern <dsahern@kernel.org>
Acked-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent a135798e

net/ipv4/tcp_metrics.c

+5 −2
Original line number Diff line number Diff line
@@ -898,11 +898,13 @@ static void tcp_metrics_flush_all(struct net *net) 
	unsigned int row;



	for (row = 0; row < max_rows; row++, hb++) {

		struct tcp_metrics_block __rcu **pp;

		struct tcp_metrics_block __rcu **pp = &hb->chain;

		bool match;



		if (!rcu_access_pointer(*pp))

			continue;



		spin_lock_bh(&tcp_metrics_lock);

		pp = &hb->chain;

		for (tm = deref_locked(*pp); tm; tm = deref_locked(*pp)) {

			match = net ? net_eq(tm_net(tm), net) :

				!refcount_read(&tm_net(tm)->ns.count);
@@ -914,6 +916,7 @@ static void tcp_metrics_flush_all(struct net *net) 
			}

		}

		spin_unlock_bh(&tcp_metrics_lock);

		cond_resched();

	}

}