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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>
This commit is contained in:
David Howells 2017-09-04 15:28:28 +01:00 committed by David S. Miller
parent 5e369aefdc
commit fdade4f69e
1 changed files with 1 additions and 2 deletions
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3
net/rxrpc/conn_service.c
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@ -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)
p = rcu_dereference_raw(p->rb_right);
else
goto done;
break;
conn = NULL;
}
} while (need_seqretry(&peer->service_conn_lock, seq));
done:
done_seqretry(&peer->service_conn_lock, seq);
_leave(" = %d", conn ? conn->debug_id : -1);
return conn;