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SubjectRe: hung task in mac80211
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i confirm this patch fixes the issue for me as well

Am 06.09.2017 um 17:04 schrieb Matteo Croce:
> On Wed, Sep 6, 2017 at 2:58 PM, Johannes Berg <johannes@sipsolutions.net> wrote:
>> On Wed, 2017-09-06 at 13:57 +0200, Matteo Croce wrote:
>>
>>> I have an hung task on vanilla 4.13 kernel which I haven't on 4.12.
>>> The problem is present both on my AP and on my notebook,
>>> so it seems it affects AP and STA mode as well.
>>> The generated messages are:
>>>
>>> INFO: task kworker/u16:6:120 blocked for more than 120 seconds.
>>> Not tainted 4.13.0 #57
>>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
>>> message.
>>> kworker/u16:6 D 0 120 2 0x00000000
>>> Workqueue: phy0 ieee80211_ba_session_work [mac80211]
>>> Call Trace:
>>> ? __schedule+0x174/0x5b0
>>> ? schedule+0x31/0x80
>>> ? schedule_preempt_disabled+0x9/0x10
>>> ? __mutex_lock.isra.2+0x163/0x480
>>> ? select_task_rq_fair+0xb9f/0xc60
>>> ? __ieee80211_start_rx_ba_session+0x135/0x4d0 [mac80211]
>>> ? __ieee80211_start_rx_ba_session+0x135/0x4d0 [mac80211]
>> Yeah - obviously as Stefano found, both take &sta->ampdu_mlme.mtx.
>>
>> Can you try this?
>>
>> diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c
>> index 2b36eff5d97e..d8d32776031e 100644
>> --- a/net/mac80211/agg-rx.c
>> +++ b/net/mac80211/agg-rx.c
>> @@ -245,10 +245,10 @@ static void ieee80211_send_addba_resp(struct ieee80211_sub_if_data *sdata, u8 *d
>> ieee80211_tx_skb(sdata, skb);
>> }
>>
>> -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)
>> +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)
>> {
>> struct ieee80211_local *local = sta->sdata->local;
>> struct tid_ampdu_rx *tid_agg_rx;
>> @@ -267,7 +267,7 @@ void __ieee80211_start_rx_ba_session(struct sta_info *sta,
>> ht_dbg(sta->sdata,
>> "STA %pM requests BA session on unsupported tid %d\n",
>> sta->sta.addr, tid);
>> - goto end_no_lock;
>> + goto end;
>> }
>>
>> if (!sta->sta.ht_cap.ht_supported) {
>> @@ -275,14 +275,14 @@ void __ieee80211_start_rx_ba_session(struct sta_info *sta,
>> "STA %pM erroneously requests BA session on tid %d w/o QoS\n",
>> sta->sta.addr, tid);
>> /* send a response anyway, it's an error case if we get here */
>> - goto end_no_lock;
>> + goto end;
>> }
>>
>> if (test_sta_flag(sta, WLAN_STA_BLOCK_BA)) {
>> ht_dbg(sta->sdata,
>> "Suspend in progress - Denying ADDBA request (%pM tid %d)\n",
>> sta->sta.addr, tid);
>> - goto end_no_lock;
>> + goto end;
>> }
>>
>> /* sanity check for incoming parameters:
>> @@ -296,7 +296,7 @@ void __ieee80211_start_rx_ba_session(struct sta_info *sta,
>> ht_dbg_ratelimited(sta->sdata,
>> "AddBA Req with bad params from %pM on tid %u. policy %d, buffer size %d\n",
>> sta->sta.addr, tid, ba_policy, buf_size);
>> - goto end_no_lock;
>> + goto end;
>> }
>> /* determine default buffer size */
>> if (buf_size == 0)
>> @@ -311,7 +311,6 @@ 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 (test_bit(tid, sta->ampdu_mlme.agg_session_valid)) {
>> if (sta->ampdu_mlme.tid_rx_token[tid] == dialog_token) {
>> @@ -415,15 +414,25 @@ 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);
>>
>> -end_no_lock:
>> if (tx)
>> ieee80211_send_addba_resp(sta->sdata, sta->sta.addr, tid,
>> dialog_token, status, 1, buf_size,
>> timeout);
>> }
>>
>> +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);
>> +}
>> +
>> void ieee80211_process_addba_request(struct ieee80211_local *local,
>> struct sta_info *sta,
>> struct ieee80211_mgmt *mgmt,
>> diff --git a/net/mac80211/ht.c b/net/mac80211/ht.c
>> index c92df492e898..198b2d3e56fd 100644
>> --- a/net/mac80211/ht.c
>> +++ b/net/mac80211/ht.c
>> @@ -333,9 +333,9 @@ void ieee80211_ba_session_work(struct work_struct *work)
>>
>> if (test_and_clear_bit(tid,
>> sta->ampdu_mlme.tid_rx_manage_offl))
>> - __ieee80211_start_rx_ba_session(sta, 0, 0, 0, 1, tid,
>> - IEEE80211_MAX_AMPDU_BUF,
>> - false, true);
>> + ___ieee80211_start_rx_ba_session(sta, 0, 0, 0, 1, tid,
>> + IEEE80211_MAX_AMPDU_BUF,
>> + false, 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..9675814f64db 100644
>> --- a/net/mac80211/ieee80211_i.h
>> +++ b/net/mac80211/ieee80211_i.h
>> @@ -1760,6 +1760,10 @@ 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);
>> +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);
>> 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,
>>
>> johannes
> I confirm that this patch fixes the hang too.
> I'm curious to see if there are noticeable performance differences
> between the two solutions.
>
> Cheers,


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