Agreed. I'll use rcu_access_pointer() in v2; it expresses the final pointer fetch more directly once unregister has quiesced the updaters.
Thanks, Yousef On Mon, 06 Jul 2026 17:10:35 +0200, Miquel Raynal <[email protected]> wrote: > Hello Yousef, > > On 03/07/2026 at 04:19:42 -07, Yousef Alhouseen <[email protected]> > wrote: > > > Hello Miquel, > > > > After ieee802154_unregister_hw() returns, the driver callbacks that > > can replace phy->pib have been quiesced, and hwsim_del() has exclusive > > ownership of the final teardown. The pointer is no longer being > > fetched inside an RCU read-side critical section, so rcu_dereference() > > is not appropriate there. > > That's right. > > > rcu_dereference_protected(phy->pib, 1) expresses that there can no > > longer be a concurrent updater at that point; the protection condition > > is the completed unregister rather than a locally held lock. The value > > is only fetched so the final object can be passed to kfree_rcu(). > > While I believe this is indeed true, it actually feels slightly overkill > since there is no updater anymore and, as far as I understand, the only > thing that we need here is to get the pointer value for freeing, right? > > > rcu_access_pointer() would also be sufficient for that limited use if > > you prefer it, and I can use that spelling in a v2. > > If you don't mind, I feel like rcu_access_pointer() is exactly what we > need here. It is also more understandable, even though I agree in > practice there are no differences in this case. > > Thanks, > Miquèl
