On Mon, Apr 6, 2020 at 7:31 PM Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote: > > On Mon, 2020-04-06 at 19:25 +0530, Krishna Chaitanya wrote: > > On Mon, Apr 6, 2020 at 6:57 PM Kalle Valo <kvalo@xxxxxxxxxxxxxx> wrote: > > > Sumit Garg <sumit.garg@xxxxxxxxxx> writes: > > > > > > > On Mon, 6 Apr 2020 at 18:38, Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote: > > > > > On Mon, 2020-04-06 at 16:04 +0300, Kalle Valo wrote: > > > > > > Johannes Berg <johannes@xxxxxxxxxxxxxxxx> writes: > > > > > > > > > > > > > On Mon, 2020-04-06 at 15:52 +0300, Kalle Valo wrote: > > > > > > > > Johannes Berg <johannes@xxxxxxxxxxxxxxxx> writes: > > > > > > > > > > > > > > > > > On Mon, 2020-04-06 at 15:44 +0300, Kalle Valo wrote: > > > > > > > > > > > user-space ieee80211_register_hw() RX IRQ > > > > > > > > > > > +++++++++++++++++++++++++++++++++++++++++++++ > > > > > > > > > > > | | | > > > > > > > > > > > |<---wlan0---wiphy_register() | > > > > > > > > > > > |----start wlan0---->| | > > > > > > > > > > > | |<---IRQ---(RX packet) > > > > > > > > > > > | Kernel crash | > > > > > > > > > > > | due to unallocated | > > > > > > > > > > > | workqueue. | > > > > > > > > > > > > > > > > > > [snip] > > > > > > > > > > > > > > > > > > > I have understood that no frames should be received until mac80211 calls > > > > > > > > > > struct ieee80211_ops::start: > > > > > > > > > > > > > > > > > > > > * @start: Called before the first netdevice attached to the hardware > > > > > > > > > > * is enabled. This should turn on the hardware and must turn on > > > > > > > > > > * frame reception (for possibly enabled monitor interfaces.) > > > > > > > > > > > > > > > > > > True, but I think he's saying that you can actually add and configure an > > > > > > > > > interface as soon as the wiphy is registered? > > > > > > > > > > > > > > > > With '<---IRQ---(RX packet)' I assumed wcn36xx is delivering a frame to > > > > > > > > mac80211 using ieee80211_rx(), but of course I'm just guessing here. > > > > > > > > > > > > > > Yeah, but that could be legitimate? > > > > > > > > > > > > Ah, I misunderstood then. The way I have understood is that no rx frames > > > > > > should be delivered (= calling ieee80211_rx()_ before start() is called, > > > > > > but if that's not the case please ignore me :) > > > > > > > > > > No no, that _is_ the case. But I think the "start wlan0" could end up > > > > > calling it? > > > I am still confused, without ieee80211_if_add how can the userspace > > bring up the interface? > > It can add its own interface. Maybe that won't be 'wlan0' but something > else? > > like > > iw phy0 interface add wlan0 type station > ip link set wlan0 up Ah okay, got it, thanks. Very narrow window though :-) as the alloc_ordered_workqueue doesn't need RTNL and there is a long way to go to do if_add() from user and setup the driver for interrupts. Again depends on the driver though, it should properly handle pending ieee80211_register_hw() with start().
