Re: [PATCH v4a 00/38] timers: Use timer_shutdown*() before freeing timers

Julia Lawall
2022-11-06T03:05:25Z

On Sat, 5 Nov 2022, Steven Rostedt wrote:

> On Sun, 6 Nov 2022 07:08:48 +0800 (+08)
> Julia Lawall <julia.lawall@inria.fr> wrote:
>
> > Various suggestions:
> >
> > 1. On your ... put when strict and then on a separate line put when !=
> > ptr. The when strict will get rid of the goto problem (usually a
> > desirable feature, but not here) and the when != ptr will be sure that ptr
> > is not used before the free.
>
> You mean ptr->timer.function? because it's allowed to be touched. Only
> this case is weird (and I believe I covered it).
>
> Not sure what you mean by "put when strict" I added:
>
> ... when strict
>
> Thinking that's what you meant (examples would be easier to understand,
> than descriptions). And it didn't cover the return case. Does it only
> cover gotos?
>
> See drivers/net/wireless/intel/iwlwifi/mvm/sta.c for the false positive case:
>
> del_timer_sync(&baid_data->session_timer);
> [..]

But there is a kfree_rcu(baid_data, rcu_head); right below. So it looks
fine?

julia

> return 0;
>
> out_free:
> kfree(baid_data);
> return ret;
> }
>
> That "return 0" should make the match fail.
>
> >
> > 2. If you want to handle the initialization of the function field, then
> > you can duplicate the rule and add the removal of that assignment in the
> > first one. This only seems worth it if it is a very common case.
> > Otherwise, I would agree with Linus and just take care of it by hand
> > later.
>
> No, Linus wants the script to not touch the initialization case. That
> is, currently, the script does the conversion (which also initializes
> it), and the timer.function = NULL is just redundant.
>
> What Linus wanted, was my script to do nothing in this case. But I
> figured this part out.
>
> >
> > 3. Running the rule three times seems to me like a reasonable choice. Or
> > you could duplicate the rule three times. But that would be more script
> > to read through. If this is not a common case, though, you could probably
> > also fix the one up later by hand.
>
> Yeah, that's fine.
>
> I'm just looking for how to avoid the goto / return case.
>
> -- Steve
>