Re: [PATCH rcu/dev 3/3] net: Use call_rcu_flush() for dst_destroy_rcu

[Eric Dumazet]

On Thu, Nov 17, 2022 at 9:42 AM Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote:
>

>
> Yes, I agree. Your comments here have not been useful (or respectful)
> so I am Ok with that.
>
>  - Joel

Well, I have discovered that some changes went in networking tree
without network maintainers being involved nor CCed.

What can I say ?

It seems I have no say, right ?


commit f32846476afbe1f296c41d036219178b3dfb6a9d
Author: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Date:   Sun Oct 16 16:23:04 2022 +0000

    rxrpc: Use call_rcu_flush() instead of call_rcu()

    call_rcu() changes to save power may cause slowness. Use the
    call_rcu_flush() API instead which reverts to the old behavior.

    We find this via inspection that the RCU callback does a wakeup of a
    thread. This usually indicates that something is waiting on it. To be
    safe, let us use call_rcu_flush() here instead.

    Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
    Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

diff --git a/net/rxrpc/conn_object.c b/net/rxrpc/conn_object.c
index 22089e37e97f0628f780855f9e219e5c33d4afa1..fdcfb509cc4434b0781b76623532aff9c854ce60
100644
--- a/net/rxrpc/conn_object.c
+++ b/net/rxrpc/conn_object.c
@@ -253,7 +253,7 @@ void rxrpc_kill_connection(struct rxrpc_connection *conn)
         * must carry a ref on the connection to prevent us getting here whilst
         * it is queued or running.
         */
-       call_rcu(&conn->rcu, rxrpc_destroy_connection);
+       call_rcu_flush(&conn->rcu, rxrpc_destroy_connection);
 }

 /*