Commit fdade4f6 authored Sep 04, 2017 by David Howells Committed by David S. Miller Sep 05, 2017

rxrpc: Make service connection lookup always check for retry



When an RxRPC service packet comes in, the target connection is looked up
by an rb-tree search under RCU and a read-locked seqlock; the seqlock retry
check is, however, currently skipped if we got a match, but probably
shouldn't be in case the connection we found gets replaced whilst we're
doing a search.

Make the lookup procedure always go through need_seqretry(), even if the
lookup was successful.  This makes sure we always pick up on a write-lock
event.

On the other hand, since we don't take a ref on the object, but rely on RCU
to prevent its destruction after dropping the seqlock, I'm not sure this is
necessary.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 5e369aef

net/rxrpc/conn_service.c

+1 −2

Original line number	Original line	Diff line number	Diff line
	@@ -50,12 +50,11 @@ struct rxrpc_connection rxrpc_find_service_conn_rcu(struct rxrpc_peer peer,
	else if (conn->proto.index_key > k.index_key)		else if (conn->proto.index_key > k.index_key)
	p = rcu_dereference_raw(p->rb_right);		p = rcu_dereference_raw(p->rb_right);
	else		else
	goto done;		break;
	conn = NULL;		conn = NULL;
	}		}
	} while (need_seqretry(&peer->service_conn_lock, seq));		} while (need_seqretry(&peer->service_conn_lock, seq));

	done:
	done_seqretry(&peer->service_conn_lock, seq);		done_seqretry(&peer->service_conn_lock, seq);
	_leave(" = %d", conn ? conn->debug_id : -1);		_leave(" = %d", conn ? conn->debug_id : -1);
	return conn;		return conn;