On Thu, 23 Apr 2020 at 02:29, Hauke Mehrtens <hauke@xxxxxxxxxx> wrote:
>
> Hi,
>
> Since commit 52e04b4ce5d0 ("mac80211: fix race in
> ieee80211_register_hw()") the debugfs entries for mac80211 drivers are
> broken.
> https://git.kernel.org/linus/52e04b4ce5d03775b6a78f3ed1097480faacc9fd
>
> Felix reported that the file /sys/kernel/debug/ieee80211/phy0/rc is now
> located at /sys/kernel/debug/rc.
>
> Before this commit we had the following flow:
> 1. wiphy_register()
> -> creates /sys/kernel/debug/ieee80211/phy0/
> -> fill rdev->wiphy.debugfsdir pointer
> 2. ieee80211_init_rate_ctrl_alg()
> -> call rate_control_alloc()
> -> use rdev->wiphy.debugfsdir pointer to
> create /sys/kernel/debug/ieee80211/phy0/rc/
>
> This works like expected.
>
>
> With the commit the flow in ieee80211_register_hw() is the other way around:
> 2. ieee80211_init_rate_ctrl_alg()
> -> call rate_control_alloc()
> -> use rdev->wiphy.debugfsdir pointer (now NULL) to
> create /sys/kernel/debug/rc/
> 2. wiphy_register()
> -> creates /sys/kernel/debug/ieee80211/phy0/
> -> fill rdev->wiphy.debugfsdir pointer
>
Thanks for the detailed report. I missed to notice this hidden debugfs
dependency on "wiphy_register()". To address this issue, I think it's
reasonable to move creation of wiphy debugfs directory during
allocation of wiphy device as per following change (untested though):
diff --git a/net/wireless/core.c b/net/wireless/core.c
index 341402b..239e9ff 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -473,6 +473,10 @@ struct wiphy *wiphy_new_nm(const struct
cfg80211_ops *ops, int sizeof_priv,
}
}
+ /* add to debugfs */
+ rdev->wiphy.debugfsdir = debugfs_create_dir(wiphy_name(&rdev->wiphy),
+ ieee80211_debugfs_dir);
+
INIT_LIST_HEAD(&rdev->wiphy.wdev_list);
INIT_LIST_HEAD(&rdev->beacon_registrations);
spin_lock_init(&rdev->beacon_registrations_lock);
@@ -903,10 +907,6 @@ int wiphy_register(struct wiphy *wiphy)
list_add_rcu(&rdev->list, &cfg80211_rdev_list);
cfg80211_rdev_list_generation++;
- /* add to debugfs */
- rdev->wiphy.debugfsdir = debugfs_create_dir(wiphy_name(&rdev->wiphy),
- ieee80211_debugfs_dir);
-
cfg80211_debugfs_rdev_add(rdev);
nl80211_notify_wiphy(rdev, NL80211_CMD_NEW_WIPHY);
With this change we can remove this hidden debugfs dependency. Please
give it a try and let me know if it works for you.
-Sumit
>
> This patch was backported to multiple stable kernel versions:
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.4.y&id=a8ce3412e8a22279e1bdc81c3c2bacd3785c1577
>
> Hauke
