Hello. Recently I bought a TP-Link TL-WN821N v3 802.11n USB adaptor, and tried to use it as an access point for a small Wireless LAN. It works fine so far, except of one issue. Quite often to be really annoying, it stops working with the following message in kernel log: Jul 5 09:51:26 gnome vmunix: [133814.449408] ath: Unable to remove station entry for: 38:aa:3c:02:07:f1 after this, the interface is stuck, it can't be seen over WIFI, and any attempt to do anything with it inside the host results in more processes entering D state (initially right when this happens, there's a kworker process in D state). For example, `rmmod ath9k_htc' - which appears to be a topmost module on the stack - results in rmmod entering D state, with the following stack: rmmod D 000000010266c10c 0 10684 10643 0x00000000 ffffffff8148b020 0000000000000082 0000000000012400 ffff88012ae9d7d0 ffff880114843fd8 ffff880114843fd8 ffff880114843fd8 ffff88012ae9d7d0 0000000125aa5040 ffffffff8148b020 0000000000012400 ffff8801298cb500 Call Trace: [<ffffffff81367a59>] ? __schedule+0x3a9/0x960 [<ffffffff810558f0>] ? usleep_range+0x40/0x40 [<ffffffff81368e38>] ? __mutex_lock_slowpath+0xc8/0x140 [<ffffffff813689ba>] ? mutex_lock+0x1a/0x40 [<ffffffffa025bc66>] ? ath9k_wmi_cmd+0xc6/0x200 [ath9k_htc] [<ffffffffa02614d8>] ? ath9k_regread+0x38/0x50 [ath9k_htc] [<ffffffffa0076849>] ? ath_hw_keyreset+0x59/0x220 [ath] [<ffffffffa0076a2d>] ? ath_key_delete+0x1d/0xdc [ath] [<ffffffffa025edc5>] ? ath9k_htc_set_key+0x85/0x130 [ath9k_htc] [<ffffffffa0230d19>] ? ieee80211_key_disable_hw_accel+0x89/0x130 [mac80211] [<ffffffffa0230ddc>] ? __ieee80211_key_destroy+0x1c/0x80 [mac80211] [<ffffffffa0231505>] ? ieee80211_free_keys+0x45/0x80 [mac80211] [<ffffffffa02233a7>] ? ieee80211_do_stop+0x1f7/0x5c0 [mac80211] [<ffffffff812d9f40>] ? dev_deactivate_many+0x1f0/0x240 [<ffffffffa0223785>] ? ieee80211_stop+0x15/0x20 [mac80211] [<ffffffff812bc505>] ? __dev_close_many+0x85/0xd0 [<ffffffff812bc638>] ? dev_close_many+0x98/0x110 [<ffffffff812bc788>] ? rollback_registered_many+0xd8/0x250 [<ffffffff812bc90e>] ? unregister_netdevice_many+0xe/0x60 [<ffffffffa0222f00>] ? ieee80211_remove_interfaces+0xc0/0x100 [mac80211] [<ffffffffa0211096>] ? ieee80211_unregister_hw+0x46/0x110 [mac80211] [<ffffffffa02624c4>] ? ath9k_htc_disconnect_device+0x54/0xd0 [ath9k_htc] [<ffffffffa025b3a2>] ? ath9k_hif_usb_disconnect+0x52/0x150 [ath9k_htc] [<ffffffffa005dd52>] ? usb_unbind_interface+0x42/0x150 [usbcore] [<ffffffff81274546>] ? __device_release_driver+0x76/0xe0 [<ffffffff81274bf0>] ? driver_detach+0xa0/0xb0 [<ffffffff812743d0>] ? bus_remove_driver+0x70/0xc0 [<ffffffffa005d7a6>] ? usb_deregister+0xa6/0xc0 [usbcore] [<ffffffffa0262d36>] ? ath9k_htc_exit+0x6/0x16 [ath9k_htc] [<ffffffff81080ee2>] ? sys_delete_module+0x132/0x260 [<ffffffff8136a245>] ? page_fault+0x25/0x30 [<ffffffff81371552>] ? system_call_fastpath+0x16/0x1b followed by: Jul 5 10:02:27 gnome vmunix: [134474.473451] ath: Unable to remove interface at idx: 0 (rmmod is stuck forever). Now, in order to make the interface to work again, the only way I found so far is to _reboot_ the machine. For example, re-plugging the USB cord does not help, because, as far as I can see, the driver is in some weird state and can't initialize the new interface. This is a 3.2.0-stable kernel (right now 3.2.46), x86-64 (amd64), self-compiled, without additional patches. There are a few references to this message on the 'net, including one mentioning this very card (in russian) -- http://forums.opensuse.org/p-russian/dhydhdhdhdhundhdhdh/1046-1077-1083-1077-1079-1086/469022-wifi-usb-tp-link-tl-wn821n.html they claim the problem has been fixed for _some_ by upgrading the BIOS on the motherboard. Maybe this is actually related, because as far as I can tell, this started happening _after_ I upgraded BIOS on my motherboard, so it may be related to the bios changes. I don't recall whenever I noticed this erratic behavour before I upgraded BIOS. Looking at the BIOS history, I don't see anything interesting about USB in the changelog, except this: * Fixed issue with Fast Boot so USB devices still work under DOS if USB Optimization is enabled. This is an intel atom-based D2500CC board, with the latest BIOS. I had to update bios because of another issue which is now fixed, but I can't go back to the old bios because the old one was too old and current motherboard refuses to flash it. What can be done to diagnose the problem? I can give a more recent kernel a try, but I'd love to see it fixed for a -stable kernel which is used by several major distributions. Also, the problem is not easy to trigger, the system may work for a few days without issues or may stop working in a few hours, irrespective of the load (f.e. the above example at 09:51 was me awakening my android phone just to see what time it is now, and it trying to connect/disconnect to/from the default wifi network -- there were no other devices using wifi at that time). Thanks, /mjt -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
