From: Wen Gong <quic_wgong@xxxxxxxxxxx>
Running this test in a loop it is easy to reproduce an rtnl deadlock:
iw reg set FI
ifconfig wlan0 down
What happens is that thread A (workqueue) tries to update the regulatory:
try to acquire the rtnl_lock of ar->regd_update_work
rtnl_lock
ath12k_regd_update [ath12k]
ath12k_regd_update_work [ath12k]
process_one_work
worker_thread
kthread
ret_from_fork
And thread B (ifconfig) tries to stop the interface:
try to cancel_work_sync(&ar->regd_update_work) in ath12k_mac_op_stop().
ifconfig 3109 [003] 2414.232506: probe:
ath12k_mac_op_stop [ath12k]
drv_stop [mac80211]
ieee80211_do_stop [mac80211]
ieee80211_stop [mac80211]
The sequence of deadlock is:
1. Thread B calls rtnl_lock().
2. Thread A starts to run and calls rtnl_lock() from within
ath12k_regd_update_work(), then enters wait state because the lock is owned by
thread B.
3. Thread B tries to call cancel_work_sync(&ar->regd_update_work), but thread A is in
ath12k_regd_update_work() waiting for rtnl_lock(). So cancel_work_sync()
forever waits for ath12k_regd_update_work() to finish and we have a deadlock.
Change to use regulatory_set_wiphy_regd(), which is the asynchronous version of
regulatory_set_wiphy_regd_sync(). This way rtnl & wiphy locks are not required so can
be removed, and in the end the deadlock issue can be avoided.
But a side effect introduced by the asynchronous regd update is that, some essential
information used in ath12k_reg_update_chan_list(), which would be called later in
ath12k_regd_update(), might has not been updated by cfg80211, as a result wrong
channel parameters sent to firmware.
To handle this side effect, move ath12k_reg_update_chan_list() to ath12k_reg_notifier(),
and advertise WIPHY_FLAG_NOTIFY_REGDOM_BY_DRIVER to cfg80211. This works because,
in the process of the asynchronous regd update, after the new regd is processed,
cfg80211 will notify ath12k by calling ath12k_reg_notifier(). Since all essential
information is updated at that time, we are good to do channel list update.
Please note ath12k_reg_notifier() could also be called due to other reasons, like
core/beacon/user hints etc. For them we are not allowed to call
ath12k_reg_update_chan_list() because regd has not been updated. This is done by
verifying the initiator.
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3
Signed-off-by: Wen Gong <quic_wgong@xxxxxxxxxxx>
Co-developed-by: Baochen Qiang <quic_bqiang@xxxxxxxxxxx>
Signed-off-by: Baochen Qiang <quic_bqiang@xxxxxxxxxxx>
---
drivers/net/wireless/ath/ath12k/reg.c | 35 +++++++++++++++------------
1 file changed, 20 insertions(+), 15 deletions(-)
diff --git a/drivers/net/wireless/ath/ath12k/reg.c b/drivers/net/wireless/ath/ath12k/reg.c
index 439d61f284d8..ea03f3f50e50 100644
--- a/drivers/net/wireless/ath/ath12k/reg.c
+++ b/drivers/net/wireless/ath/ath12k/reg.c
@@ -55,6 +55,24 @@ ath12k_reg_notifier(struct wiphy *wiphy, struct regulatory_request *request)
ath12k_dbg(ar->ab, ATH12K_DBG_REG,
"Regulatory Notification received for %s\n", wiphy_name(wiphy));
+ if (request->initiator == NL80211_REGDOM_SET_BY_DRIVER) {
+ ath12k_dbg(ar->ab, ATH12K_DBG_REG,
+ "driver initiated regd update\n");
+ if (ah->state != ATH12K_HW_STATE_ON)
+ return;
+
+ for_each_ar(ah, ar, i) {
+ ret = ath12k_reg_update_chan_list(ar);
+ if (ret) {
+ ath12k_warn(ar->ab,
+ "failed to update chan list for pdev %u, ret %d\n",
+ i, ret);
+ break;
+ }
+ }
+ return;
+ }
+
/* Currently supporting only General User Hints. Cell base user
* hints to be handled later.
* Hints from other sources like Core, Beacons are not expected for
@@ -211,7 +229,6 @@ int ath12k_regd_update(struct ath12k *ar, bool init)
struct ieee80211_regdomain *regd, *regd_copy = NULL;
int ret, regd_len, pdev_id;
struct ath12k_base *ab;
- int i;
ab = ar->ab;
@@ -275,11 +292,7 @@ int ath12k_regd_update(struct ath12k *ar, bool init)
goto err;
}
- rtnl_lock();
- wiphy_lock(hw->wiphy);
- ret = regulatory_set_wiphy_regd_sync(hw->wiphy, regd_copy);
- wiphy_unlock(hw->wiphy);
- rtnl_unlock();
+ ret = regulatory_set_wiphy_regd(hw->wiphy, regd_copy);
kfree(regd_copy);
@@ -290,15 +303,6 @@ int ath12k_regd_update(struct ath12k *ar, bool init)
goto skip;
ah->regd_updated = true;
- /* Apply the new regd to all the radios, this is expected to be received only once
- * since we check for ah->regd_updated and allow here only once.
- */
- for_each_ar(ah, ar, i) {
- ab = ar->ab;
- ret = ath12k_reg_update_chan_list(ar);
- if (ret)
- goto err;
- }
skip:
return 0;
err:
@@ -770,6 +774,7 @@ void ath12k_regd_update_work(struct work_struct *work)
void ath12k_reg_init(struct ieee80211_hw *hw)
{
hw->wiphy->regulatory_flags = REGULATORY_WIPHY_SELF_MANAGED;
+ hw->wiphy->flags |= WIPHY_FLAG_NOTIFY_REGDOM_BY_DRIVER;
hw->wiphy->reg_notifier = ath12k_reg_notifier;
}
base-commit: 8fb3b2b8d6d489416a7ff8a28cd4083340ad9e55
--
2.25.1
