netdev - Re: [PATCH net] rxrpc: Restore removed timer deletion

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Message-ID: <2419532.1649871672@warthog.procyon.org.uk>
Date:   Wed, 13 Apr 2022 18:41:12 +0100
From:   David Howells <dhowells@...hat.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     dhowells@...hat.com, netdev@...r.kernel.org,
        Marc Dionne <marc.dionne@...istor.com>,
        linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] rxrpc: Restore removed timer deletion

Eric Dumazet <edumazet@...gle.com> wrote:

> ok... so we have a timer and a work queue, both activating each other
> in kind of a ping pong ?

Yes.  I want to emit regular keepalive pokes.

> Any particular reason not using delayed works ?

Because there's a race between starting the keepalive timer when a new peer is
added and when the keepalive worker is resetting the timer for the next peer
in the list.  This is why I'm using timer_reduce().  delayed_work doesn't
currently have such a facility.  It's not simple to add because
try_to_grab_pending() as called from mod_delayed_work_on() cancels the timer -
which is not what I want it to do.

David