Hi On Tue, May 13, 2014 at 11:00 AM, Rajkumar Manoharan <rmanohar@xxxxxxxxxxxxxxxx> wrote: > On Tue, May 13, 2014 at 08:50:00AM +0200, David Herrmann wrote: >> Hi >> >> On Mon, May 12, 2014 at 8:43 PM, Felix Fietkau <nbd@xxxxxxxxxxx> wrote: >> > I looked into it again, the scenario where I assumed that this problem >> > could occur didn't turn out to be true. I have no idea how this crash >> > can occur. >> >> The only path that can set ah->caldata to NULL is through: >> >> ieee80211_hw_config() >> ath9k_htc_config() >> ath9k_htc_set_channel() >> ath9k_hw_reset() >> >> This happens whenever IEEE80211_CONF_OFFCHANNEL is set. >> >> Now mac80211 is way to big for me to review right now and >> ieee80211_hw_config() is used quite often. Given that the described >> call-path does no synchronization against ath9k_htc_ani_work(), all >> the callers of mac80211_hw_config(OFFCHANNEL) must guarantee that no >> ani-work is running. Is that intentional? I cannot see any of those >> functions calling into ath9k_htc_stop_ani(). This might of course be >> implicit. >> >> One call-path I see is: >> ieee80211_scan_cancel() >> cancel_delayed_work() >> >> We cannot use cancel_delayed_work_sync() here due to locking issues. >> However, this obviously races against any following >> set_channel(OFFCHANNEL) request. >> >> If there's anything I can do to debug this, let me know. I tried >> adding some printk()'s into the hot-path and it turns out to no longer >> fail then. So this really seems to be a quite small race (given that a >> bunch of simple printk()s is slow enough to work around it). > > David, > > Are you using USB devices? What is the PID/VID? I have not looked at > HTC driver perspective. Yes, I'm using the htc driver. I thought that was clear by pointing at ar9002, but I was wrong, sorry. lsusb information is: 'Bus 003 Device 056: ID 0411:017f BUFFALO INC. (formerly MelCo., Inc.) Sony UWA-BR100 802.11abgn Wireless Adapter [Atheros AR7010+AR9280]' Thanks David -- 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
