Re: [PATCH bpf-next v3 2/3] bpf: do not walk twice the hash map on free

Kumar Kartikeya Dwivedi
2024-04-30T12:53:13Z

On Tue, 30 Apr 2024 at 12:44, Benjamin Tissoires <bentiss@kernel.org> wrote:
>
> If someone stores both a timer and a workqueue in a hash map, on free, we
> would walk it twice.
> Add a check in htab_free_malloced_timers_or_wq and free the timers
> and workqueues if they are present.
>
> Fixes: 246331e3f1ea ("bpf: allow struct bpf_wq to be embedded in arraymaps and hashmaps")
> Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
>
> ---

I had forgotten how the extra_elems logic is working, turns out
everything is in the preallocated elems array and per-cpu extra_elems
stores the *pointer* to them for recycling without hitting the pcpu
allocator, so should be fine (just in case this confuses anyone else).

>
> changes in v3:
> - fix unloading of bpf_wq, again
>
> changes in v2:
> - fix wq being not freed (and static call not used)
> ---

Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>