Re: hung task in mac80211

On Wed, 06 Sep 2017 15:21:00 +0200
Johannes Berg [off-list ref] wrote:

On Wed, 2017-09-06 at 15:19 +0200, Stefano Brivio wrote:

quoted

On Wed, 06 Sep 2017 14:48:35 +0200
Johannes Berg [off-list ref] wrote:
  

quoted

I'll look in a bit - but
  

quoted

+			mutex_unlock(&sta->ampdu_mlme.mtx);
 			___ieee80211_stop_rx_ba_session(
 				sta, tid, WLAN_BACK_RECIPIENT,
 				WLAN_REASON_QSTA_TIMEOUT,
true);    

This already has three underscores so shouldn't drop.  

Right, of course.
  

quoted

[...]  

quoted

+			mutex_unlock(&sta->ampdu_mlme.mtx);
 			__ieee80211_start_rx_ba_session(sta, 0,
0,
0, 1, tid,    

maybe this one needs a ___ version then?  

Either that, or as it's a single call, perhaps just the following?
Matter of taste I guess...  

I don't think it's a matter of taste - for me, in principle, dropping
locks for small sections of code where the larger section holds it is a
bug waiting to happen. It may (may, I don't even know) be OK here, but
in general it's something to avoid.

Yes, that was based on the assumption that the initial part of
__ieee80211_start_rx_ba_session() can't really affect the AMPDU
state-machine in any way.

But sure, one small change there in the future and the assumption
doesn't hold anymore.


--
Stefano