[PATCH net] rxrpc: Fix client call queueing, waiting for channel

[PATCH net] rxrpc: Fix client call queueing, waiting for channel

[David Howells]

rxrpc_get_client_conn() adds a new call to the front of the waiting_calls
queue if the connection it's going to use already exists.  This is bad as
it allows calls to get starved out.

Fix this by adding to the tail instead.

Also change the other enqueue point in the same function to put it on the
front (ie. when we have a new connection).  This makes the point that in
the case of a new connection the new call goes at the front (though it
doesn't actually matter since the queue should be unoccupied).

Fixes: 45025bceef17 ("rxrpc: Improve management and caching of client connection objects")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
---

 net/rxrpc/conn_client.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/rxrpc/conn_client.c b/net/rxrpc/conn_client.c
index 505690dbd0be..04e62afea063 100644
--- a/net/rxrpc/conn_client.c
+++ b/net/rxrpc/conn_client.c
@@ -354,7 +354,7 @@ static int rxrpc_get_client_conn(struct rxrpc_sock *rx,
 	 * normally have to take channel_lock but we do this before anyone else
 	 * can see the connection.
 	 */
-	list_add_tail(&call->chan_wait_link, &candidate->waiting_calls);
+	list_add(&call->chan_wait_link, &candidate->waiting_calls);
 
 	if (cp->exclusive) {
 		call->conn = candidate;
@@ -433,7 +433,7 @@ static int rxrpc_get_client_conn(struct rxrpc_sock *rx,
 	call->conn = conn;
 	call->security_ix = conn->security_ix;
 	call->service_id = conn->service_id;
-	list_add(&call->chan_wait_link, &conn->waiting_calls);
+	list_add_tail(&call->chan_wait_link, &conn->waiting_calls);
 	spin_unlock(&conn->channel_lock);
 	_leave(" = 0 [extant %d]", conn->debug_id);
 	return 0;

Re: [PATCH net] rxrpc: Fix client call queueing, waiting for channel

[David Miller]

From: David Howells <dhowells@redhat.com>
Date: Sat, 09 Mar 2019 00:29:58 +0000

> rxrpc_get_client_conn() adds a new call to the front of the waiting_calls
> queue if the connection it's going to use already exists.  This is bad as
> it allows calls to get starved out.
> 
> Fix this by adding to the tail instead.
> 
> Also change the other enqueue point in the same function to put it on the
> front (ie. when we have a new connection).  This makes the point that in
> the case of a new connection the new call goes at the front (though it
> doesn't actually matter since the queue should be unoccupied).
> 
> Fixes: 45025bceef17 ("rxrpc: Improve management and caching of client connection objects")
> Signed-off-by: David Howells <dhowells@redhat.com>
> Reviewed-by: Marc Dionne <marc.dionne@auristor.com>

Applied and queued up for -stable, thanks David.