Re: [PATCH] mac80211: fix race in ieee80211_register_hw()

[Kalle Valo]

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.

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