Re: [PATCH v2 1/2] tcp/dcpp: Un-pin tw_timer

[Valentin Schneider]

On Thu, 23 Nov 2023 at 17:32, Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
>
> On Thu, Nov 23, 2023 at 3:34 PM Valentin Schneider <vschneid@xxxxxxxxxx> wrote:
> > I thought that was already the case, per inet_twsk_hashdance():
> >
> > /* tw_refcnt is set to 3 because we have :
> >  * - one reference for bhash chain.
> >  * - one reference for ehash chain.
> >  * - one reference for timer.
> >
> > and
> >
> > tw_timer_handler()
> > `\
> >   inet_twsk_kill()
> >   `\
> >     inet_twsk_put()
> >
> > So AFAICT, after we go through the hashdance, there's a reference on
> > tw_refcnt held by the tw_timer.
> > inet_twsk_deschedule_put() can race with arming the timer, but it only
> > calls inet_twsk_kill() if the timer
> > was already armed & has been deleted, so there's no risk of calling it
> > twice... If I got it right :-)
> >
>
> Again, I think you missed some details.
>
> I am OOO for a few days, I do not have time to elaborate.
>
> You will need to properly track active timer by elevating
> tw->tw_refcnt, or I guarantee something wrong will happen.
>

Gotcha, let me dig into this then!