> From: Johannes Berg <johannes.berg@xxxxxxxxx>
>
> The scan code creates an iflist_mtx -> mtx locking dependency,
> and a few other places, notably radar detection, were creating
> the opposite dependency, causing lockdep to complain. As scan
> and radar detection are mutually exclusive, the deadlock can't
> really happen in practice, but it's still bad form.
>
> A similar issue exists in the monitor mode code, but this is
> only used by channel-context drivers right now and those have
> to have hardware scan, so that also can't happen.
>
> Still, fix these issues by making some of the channel context
> code require the mtx to be held rather than acquiring it, thus
> allowing the monitor/radar callers to keep the iflist_mtx->mtx
> lock ordering.
>
> While at it, also fix access to the local->scanning variable
> in the radar code, and document that radar_detect_enabled is
> now properly protected by the mtx.
>
> Reported-by: Kalle Valo <kvalo@xxxxxxxxxxxxxxxx>
> Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
There are two little issues (see below). Otherwise this appears to fix the
problem Kalle reported, at least I can now scan and start hostap (using ath9k)
without getting this lockdep splat. If you want, add my Tested-by or Acked-by.
> @@ -1944,8 +1951,10 @@ static int ieee80211_join_mesh(struct wiphy *wiphy,
> struct net_device *dev, sdata->smps_mode = IEEE80211_SMPS_OFF;
> sdata->needed_rx_chains = sdata->local->rx_chains;
>
> + mutex_lock(&local->mtx);
> err = ieee80211_vif_use_channel(sdata, &setup->chandef,
> IEEE80211_CHANCTX_SHARED);
> + mutex_unlock(&local->mtx);
> if (err)
> return err;
local is not defined in ieee80211_join_mesh().
>
> @@ -1957,7 +1966,9 @@ static int ieee80211_leave_mesh(struct wiphy *wiphy,
> struct net_device *dev) struct ieee80211_sub_if_data *sdata =
> IEEE80211_DEV_TO_SUB_IF(dev);
>
> ieee80211_stop_mesh(sdata);
> + mutex_lock(&local->mtx);
> ieee80211_vif_release_channel(sdata);
> + mutex_unlock(&local->mtx);
>
> return 0;
> }
Same problem here.
Thanks!
Simon
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