On Wed 2022-07-06 10:58 -0700, Luis Chamberlain wrote:
> Hey Aaron, thanks again!
Hi Luis,
No problem :)
> On Mon, Jul 04, 2022 at 05:17:53PM +0100, Aaron Tomlin wrote:
> > To disable preemption in the context of add_kallsyms() is incorrect.
>
> Why, what broke? Did this used to work? Was the commit in question a
> regression then? Clarifying all this will help a lot.
Sorry for the confusion! If I understand correctly, nothing broke
intrinsically.
Rather with commit 08126db5ff73 ("module: kallsyms: Fix suspicious rcu
usage") under PREEMPT_RT=y, by disabling preemption, I introduced an
unbounded latency since the loop is not fixed which is generally frowned
upon. So, I would say this was a regression since earlier preemption was
not disabled and we would dereference RCU-protected pointers explicitly
i.e. without using the more appropriate rcu_dereference() family
of primitives. That being said, these pointers cannot change in this
context as explained previously.
Would the above be suitable - just to confirm before I send another
iteration?
Kind regards,
--
Aaron Tomlin
