On Fri, 2017-06-23 at 09:48 +0200, Jiri Slaby wrote: > > mac80211_queue is 255 which is IEEE80211_INVAL_HW_QUEUE, so it should > not be worked with at all. Funny you should find this today :-) > The invalid queue is hopefully handled in ieee80211_check_queues > after > drv_add_interface in ieee80211_do_open: > > res = drv_add_interface(local, sdata); > if (res) > goto err_stop; > res = ieee80211_check_queues(sdata, > ieee80211_vif_type_p2p(&sdata->vif)); > > > But the mvm driver still should not blindly shift 1 by 255 in > iwl_mvm_enable_txq. Should the check for the invalid queue be before > adding the interface in mac80211? Or should drivers check it in their > add_interface? Everything is actually handled well afaict, because the bug won't matter - this is a queue we'll never really stop, so we won't be looking at the (invalid) result of the calculation. I had actually been under the impression that it wasn't undefined but would just result in 0; that's clearly not true but also doesn't matter. AFAICT it even results in 0x80000000 (which makes some sense, since 255 % 32 == 31), and that's a queue number (31) that's too big for mac80211 anyway, so it would warn if we were to ever try to stop it. In later versions of the code, however, there *was* indeed a bug - we were using a u8 instead of a u32 in the code we have internally. While fixing *that* bug, I also made this catch the case of IEEE80211_INVAL_HW_QUEUE so we'll not modify the bitmap at all, which is the correct thing to do. IOW - yes, it's not nice, but it also shouldn't matter, and even if for some strange reason we tried to stop the queue we'd just get a warning from mac80211. johannes
