Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> writes: > On Mon, May 30, 2022 at 12:25:13PM +0300, Kalle Valo wrote: >> Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> writes: >> >> > Another problem to address is that the driver uses >> > ieee80211_iterate_stations_atomic() and >> > ieee80211_iterate_active_interfaces_atomic() and does register accesses >> > in the iterator. This doesn't work with USB, so iteration is done in two >> > steps now: The ieee80211_iterate_*_atomic() functions are only used to >> > collect the stations/interfaces on a list which is then iterated over >> > non-atomically in the second step. The implementation for this is >> > basically the one suggested by Ping-Ke here: >> > >> > https://lore.kernel.org/lkml/423f474e15c948eda4db5bc9a50fd391@xxxxxxxxxxx/ >> >> Isn't this racy? What guarantees that vifs are not deleted after >> ieee80211_iterate_active_interfaces_atomic() call? > > The driver mutex &rtwdev->mutex is acquired during the whole > collection/iteration process. For deleting an interface > ieee80211_ops::remove_interface would have to be called, right? > That would acquire &rtwdev->mutex as well, so I think this should be > safe. Can you add a comment to the code explaining this? And lockdep_assert_held() is a good way to guarantee that the mutex is really held. -- https://patchwork.kernel.org/project/linux-wireless/list/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
