[PATCH AUTOSEL 6.2 21/25] wifi: iwlwifi: mvm: protect TXQ list manipulation

Sasha Levin
2023-04-01T01:44:48Z

From: Johannes Berg <johannes.berg@intel.com>

[ Upstream commit 923bf981eb6ecc027227716e30701bdcc1845fbf ]

Some recent upstream debugging uncovered the fact that in
iwlwifi, the TXQ list manipulation is racy.

Introduce a new state bit for when the TXQ is completely
ready and can be used without locking, and if that's not
set yet acquire the lock to check everything correctly.

Reviewed-by: Benjamin Berg <benjamin.berg@intel.com>
Tested-by: Jose Ignacio Tornos Martinez <jtornosm@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../net/wireless/intel/iwlwifi/mvm/mac80211.c | 45 ++++++-------------
drivers/net/wireless/intel/iwlwifi/mvm/mvm.h | 2 +
drivers/net/wireless/intel/iwlwifi/mvm/ops.c | 1 +
drivers/net/wireless/intel/iwlwifi/mvm/sta.c | 25 +++++++++--
4 files changed, 39 insertions(+), 34 deletions(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c b/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c
index 5b4974181ff1c..1d46a2b345eb3 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c
@@ -760,42 +760,25 @@ static void iwl_mvm_mac_wake_tx_queue(struct ieee80211_hw *hw,
struct iwl_mvm *mvm = IWL_MAC80211_GET_MVM(hw);
struct iwl_mvm_txq *mvmtxq = iwl_mvm_txq_from_mac80211(txq);

- /*
- * Please note that racing is handled very carefully here:
- * mvmtxq->txq_id is updated during allocation, and mvmtxq->list is
- * deleted afterwards.
- * This means that if:
- * mvmtxq->txq_id != INVALID_QUEUE && list_empty(&mvmtxq->list):
- * queue is allocated and we can TX.
- * mvmtxq->txq_id != INVALID_QUEUE && !list_empty(&mvmtxq->list):
- * a race, should defer the frame.
- * mvmtxq->txq_id == INVALID_QUEUE && list_empty(&mvmtxq->list):
- * need to allocate the queue and defer the frame.
- * mvmtxq->txq_id == INVALID_QUEUE && !list_empty(&mvmtxq->list):
- * queue is already scheduled for allocation, no need to allocate,
- * should defer the frame.
- */
-
- /* If the queue is allocated TX and return. */
- if (!txq->sta || mvmtxq->txq_id != IWL_MVM_INVALID_QUEUE) {
- /*
- * Check that list is empty to avoid a race where txq_id is
- * already updated, but the queue allocation work wasn't
- * finished
- */
- if (unlikely(txq->sta && !list_empty(&mvmtxq->list)))
- return;
-
+ if (likely(test_bit(IWL_MVM_TXQ_STATE_READY, &mvmtxq->state)) ||
+ !txq->sta) {
iwl_mvm_mac_itxq_xmit(hw, txq);
return;
}

- /* The list is being deleted only after the queue is fully allocated. */
- if (!list_empty(&mvmtxq->list))
- return;
+ /* iwl_mvm_mac_itxq_xmit() will later be called by the worker
+ * to handle any packets we leave on the txq now
+ */

- list_add_tail(&mvmtxq->list, &mvm->add_stream_txqs);
- schedule_work(&mvm->add_stream_wk);
+ spin_lock_bh(&mvm->add_stream_lock);
+ /* The list is being deleted only after the queue is fully allocated. */
+ if (list_empty(&mvmtxq->list) &&
+ /* recheck under lock */
+ !test_bit(IWL_MVM_TXQ_STATE_READY, &mvmtxq->state)) {
+ list_add_tail(&mvmtxq->list, &mvm->add_stream_txqs);
+ schedule_work(&mvm->add_stream_wk);
+ }
+ spin_unlock_bh(&mvm->add_stream_lock);
}

#define CHECK_BA_TRIGGER(_mvm, _trig, _tid_bm, _tid, _fmt...) \
diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/mvm.h b/drivers/net/wireless/intel/iwlwifi/mvm/mvm.h
index 3146b3d02bae8..157de77e129e4 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/mvm.h
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/mvm.h
@@ -731,6 +731,7 @@ struct iwl_mvm_txq {
atomic_t tx_request;
#define IWL_MVM_TXQ_STATE_STOP_FULL 0
#define IWL_MVM_TXQ_STATE_STOP_REDIRECT 1
+#define IWL_MVM_TXQ_STATE_READY 2
unsigned long state;
};

@@ -829,6 +830,7 @@ struct iwl_mvm {
struct iwl_mvm_tvqm_txq_info tvqm_info[IWL_MAX_TVQM_QUEUES];
};
struct work_struct add_stream_wk; /* To add streams to queues */
+ spinlock_t add_stream_lock;

const char *nvm_file_name;
struct iwl_nvm_data *nvm_data;
diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/ops.c b/drivers/net/wireless/intel/iwlwifi/mvm/ops.c
index f43e617fb451f..c49a2a1ee4867 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/ops.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/ops.c
@@ -1194,6 +1194,7 @@ iwl_op_mode_mvm_start(struct iwl_trans *trans, const struct iwl_cfg *cfg,
INIT_DELAYED_WORK(&mvm->scan_timeout_dwork, iwl_mvm_scan_timeout_wk);
INIT_WORK(&mvm->add_stream_wk, iwl_mvm_add_new_dqa_stream_wk);
INIT_LIST_HEAD(&mvm->add_stream_txqs);
+ spin_lock_init(&mvm->add_stream_lock);

init_waitqueue_head(&mvm->rx_sync_waitq);

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/sta.c b/drivers/net/wireless/intel/iwlwifi/mvm/sta.c
index 21ad7b85c434c..9caae77995ca9 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/sta.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/sta.c
@@ -384,8 +384,11 @@ static int iwl_mvm_disable_txq(struct iwl_mvm *mvm, struct ieee80211_sta *sta,
struct iwl_mvm_txq *mvmtxq =
iwl_mvm_txq_from_tid(sta, tid);

- mvmtxq->txq_id = IWL_MVM_INVALID_QUEUE;
+ spin_lock_bh(&mvm->add_stream_lock);
list_del_init(&mvmtxq->list);
+ clear_bit(IWL_MVM_TXQ_STATE_READY, &mvmtxq->state);
+ mvmtxq->txq_id = IWL_MVM_INVALID_QUEUE;
+ spin_unlock_bh(&mvm->add_stream_lock);
}

/* Regardless if this is a reserved TXQ for a STA - mark it as false */
@@ -479,8 +482,11 @@ static int iwl_mvm_remove_sta_queue_marking(struct iwl_mvm *mvm, int queue)
disable_agg_tids |= BIT(tid);
mvmsta->tid_data[tid].txq_id = IWL_MVM_INVALID_QUEUE;

- mvmtxq->txq_id = IWL_MVM_INVALID_QUEUE;
+ spin_lock_bh(&mvm->add_stream_lock);
list_del_init(&mvmtxq->list);
+ clear_bit(IWL_MVM_TXQ_STATE_READY, &mvmtxq->state);
+ mvmtxq->txq_id = IWL_MVM_INVALID_QUEUE;
+ spin_unlock_bh(&mvm->add_stream_lock);
}

mvmsta->tfd_queue_msk &= ~BIT(queue); /* Don't use this queue anymore */
@@ -1444,12 +1450,22 @@ void iwl_mvm_add_new_dqa_stream_wk(struct work_struct *wk)
* a queue in the function itself.
*/
if (iwl_mvm_sta_alloc_queue(mvm, txq->sta, txq->ac, tid)) {
+ spin_lock_bh(&mvm->add_stream_lock);
list_del_init(&mvmtxq->list);
+ spin_unlock_bh(&mvm->add_stream_lock);
continue;
}

- list_del_init(&mvmtxq->list);
+ /* now we're ready, any remaining races/concurrency will be
+ * handled in iwl_mvm_mac_itxq_xmit()
+ */
+ set_bit(IWL_MVM_TXQ_STATE_READY, &mvmtxq->state);
+
local_bh_disable();
+ spin_lock(&mvm->add_stream_lock);
+ list_del_init(&mvmtxq->list);
+ spin_unlock(&mvm->add_stream_lock);
+
iwl_mvm_mac_itxq_xmit(mvm->hw, txq);
local_bh_enable();
}
@@ -1864,8 +1880,11 @@ static void iwl_mvm_disable_sta_queues(struct iwl_mvm *mvm,
struct iwl_mvm_txq *mvmtxq =
iwl_mvm_txq_from_mac80211(sta->txq[i]);

+ spin_lock_bh(&mvm->add_stream_lock);
mvmtxq->txq_id = IWL_MVM_INVALID_QUEUE;
list_del_init(&mvmtxq->list);
+ clear_bit(IWL_MVM_TXQ_STATE_READY, &mvmtxq->state);
+ spin_unlock_bh(&mvm->add_stream_lock);
}
}

--
2.39.2