Johannes Berg <johannes@xxxxxxxxxxxxxxxx> writes: > On Tue, 2021-11-30 at 12:32 +0100, Toke Høiland-Jørgensen wrote: >> Luca Coelho <luca@xxxxxxxxx> writes: >> >> > On Mon, 2021-11-29 at 14:54 +0100, Toke Høiland-Jørgensen wrote: >> > > Luca Coelho <luca@xxxxxxxxx> writes: >> > > >> > > > From: Johannes Berg <johannes.berg@xxxxxxxxx> >> > > > >> > > > When we call ieee80211_agg_start_txq(), that will in turn call >> > > > schedule_and_wake_txq(). Called from ieee80211_stop_tx_ba_cb() >> > > > this is done under sta->lock, which leads to certain circular >> > > > lock dependencies, as reported by Chris Murphy: >> > > > https://lore.kernel.org/r/CAJCQCtSXJ5qA4bqSPY=oLRMbv-irihVvP7A2uGutEbXQVkoNaw@xxxxxxxxxxxxxx >> > > > >> > > > In general, ieee80211_agg_start_txq() is usually not called >> > > > with sta->lock held, only in this one place. But it's always >> > > > called with sta->ampdu_mlme.mtx held, and that's therefore >> > > > clearly sufficient. >> > > > >> > > > Change ieee80211_stop_tx_ba_cb() to also call it without the >> > > > sta->lock held, by factoring it out of ieee80211_remove_tid_tx() >> > > > (which is only called in this one place). >> > > > >> > > > This breaks the locking chain and makes it less likely that >> > > > we'll have similar locking chain problems in the future. >> > > > >> > > > Reported-by: Chris Murphy <lists@xxxxxxxxxxxxxxxxx> >> > > > Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx> >> > > > Signed-off-by: Luca Coelho <luciano.coelho@xxxxxxxxx> >> > > >> > > Does this need a fixes: tag? >> > >> > Hi Toke, >> > >> > Neither Johannes nor Chris pointed to any specific patch that this >> > commit is fixing. If you know the exact commit that broke this, I can >> > add the tag and send v2. >> >> Well, it looks like the code you're changing comes all the way back from: >> ba8c3d6f16a1 ("mac80211: add an intermediate software queue implementation") >> >> Maybe Johannes can comment on whether it's appropriate to include this, >> or if the code changed too much in the meantime... >> > > I think that probably makes sense, and I guess I can include that tag > when I apply it. > > I suspect the reason I didn't do it internally (we have a different tag > though, so that's no excuse) is that there we didn't care until iwlwifi > actually gained TXQ support. Right, makes sense - thanks! :) -Toke
