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SubjectRe: hung task in mac80211
On Wed, 06 Sep 2017 14:58:48 +0200
Johannes Berg <johannes@sipsolutions.net> wrote:

> +void __ieee80211_start_rx_ba_session(struct sta_info *sta,
> + u8 dialog_token, u16 timeout,
> + u16 start_seq_num, u16 ba_policy, u16 tid,
> + u16 buf_size, bool tx, bool auto_seq)
> +{
> + mutex_lock(&sta->ampdu_mlme.mtx);
> + ___ieee80211_start_rx_ba_session(sta, dialog_token, timeout,
> + start_seq_num, ba_policy, tid,
> + buf_size, tx, auto_seq);
> + mutex_unlock(&sta->ampdu_mlme.mtx);
> +}
> +

Sorry for the extended bothering :) but here, you're extending quite a
bit the scope of the lock also when__ieee80211_start_rx_ba_session() is
called by ieee80211_process_addba_request(). No idea what the hit can
be, but we can't safely assume it's nothing either. What about simply
introducing a 'ampdu_mlme_lock_held' argument instead? Something like:

diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c
index 2b36eff5d97e..35a9eff1ec66 100644
--- a/net/mac80211/agg-rx.c
+++ b/net/mac80211/agg-rx.c
@@ -248,7 +248,8 @@ static void ieee80211_send_addba_resp(struct ieee80211_sub_if_data *sdata, u8 *d
void __ieee80211_start_rx_ba_session(struct sta_info *sta,
u8 dialog_token, u16 timeout,
u16 start_seq_num, u16 ba_policy, u16 tid,
- u16 buf_size, bool tx, bool auto_seq)
+ u16 buf_size, bool tx, bool auto_seq,
+ bool ampdu_mlme_lock_held)
{
struct ieee80211_local *local = sta->sdata->local;
struct tid_ampdu_rx *tid_agg_rx;
@@ -311,7 +312,8 @@ void __ieee80211_start_rx_ba_session(struct sta_info *sta,
buf_size, sta->sta.addr);

/* examine state machine */
- mutex_lock(&sta->ampdu_mlme.mtx);
+ if (!ampdu_mlme_lock_held)
+ mutex_lock(&sta->ampdu_mlme.mtx);

if (test_bit(tid, sta->ampdu_mlme.agg_session_valid)) {
if (sta->ampdu_mlme.tid_rx_token[tid] == dialog_token) {
@@ -415,7 +417,8 @@ void __ieee80211_start_rx_ba_session(struct sta_info *sta,
__clear_bit(tid, sta->ampdu_mlme.unexpected_agg);
sta->ampdu_mlme.tid_rx_token[tid] = dialog_token;
}
- mutex_unlock(&sta->ampdu_mlme.mtx);
+ if (!ampdu_mlme_lock_held)
+ mutex_unlock(&sta->ampdu_mlme.mtx);

end_no_lock:
if (tx)
@@ -445,7 +448,7 @@ void ieee80211_process_addba_request(struct ieee80211_local *local,

__ieee80211_start_rx_ba_session(sta, dialog_token, timeout,
start_seq_num, ba_policy, tid,
- buf_size, true, false);
+ buf_size, true, false, false);
}

void ieee80211_manage_rx_ba_offl(struct ieee80211_vif *vif,
diff --git a/net/mac80211/ht.c b/net/mac80211/ht.c
index c92df492e898..59ba67e8942f 100644
--- a/net/mac80211/ht.c
+++ b/net/mac80211/ht.c
@@ -335,7 +335,7 @@ void ieee80211_ba_session_work(struct work_struct *work)
sta->ampdu_mlme.tid_rx_manage_offl))
__ieee80211_start_rx_ba_session(sta, 0, 0, 0, 1, tid,
IEEE80211_MAX_AMPDU_BUF,
- false, true);
+ false, true, true);

if (test_and_clear_bit(tid + IEEE80211_NUM_TIDS,
sta->ampdu_mlme.tid_rx_manage_offl))
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 2197c62a0a6e..5d494ac65853 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1759,7 +1759,8 @@ void __ieee80211_stop_rx_ba_session(struct sta_info *sta, u16 tid,
void __ieee80211_start_rx_ba_session(struct sta_info *sta,
u8 dialog_token, u16 timeout,
u16 start_seq_num, u16 ba_policy, u16 tid,
- u16 buf_size, bool tx, bool auto_seq);
+ u16 buf_size, bool tx, bool auto_seq,
+ bool ampdu_mlme_lock_held);
void ieee80211_sta_tear_down_BA_sessions(struct sta_info *sta,
enum ieee80211_agg_stop_reason reason);
void ieee80211_process_delba(struct ieee80211_sub_if_data *sdata,
--
Stefano

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