Re: hung task in mac80211

[Sebastian Gottschall <s.gottschall@dd-wrt.com>]

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,


-- 
Mit freundlichen Grüssen / Regards

Sebastian Gottschall / CTO

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