On Wed, Oct 13, 2010 at 10:48 AM, Ben Greear <greearb@xxxxxxxxxxxxxxx> wrote: > On 10/13/2010 10:29 AM, Luis R. Rodriguez wrote: >> >> On Wed, Oct 13, 2010 at 10:12 AM, Ben Greear<greearb@xxxxxxxxxxxxxxx> >> Âwrote: >>> >>> On 10/12/2010 11:40 AM, Luis R. Rodriguez wrote: >>>> >>>> On Tue, Oct 12, 2010 at 11:35 AM, Ben Greear<greearb@xxxxxxxxxxxxxxx> >>>> Âwrote: >>>>> >>>>> On 10/11/2010 11:10 PM, Luis R. Rodriguez wrote: >>>>>> >>>>>> On Mon, Oct 11, 2010 at 8:27 PM, Ben Greear<greearb@xxxxxxxxxxxxxxx> >>>>>> Âwrote: >>>>> >>>>>>> Another thing I was thinking about: ÂMaybe the queue of skbs and dma >>>>>>> addresses >>>>>>> in ath9k is getting corrupted by multiple VIFs trying to write at >>>>>>> once? >>>>>>> ÂMaybe >>>>>>> some locking is needed in the xmit path? >>>>>> >>>>>> That was my second hunch. My first shot was to use spin_lock_irqsave() >>>>>> over the the uses of the rxbuf list and that seemed to help but I >>>>>> still managed to get a poison eventually. My next item to check for is >>>>>> of the permissibility of creating too much pressure to the point we >>>>>> end up looping over the rxbuf list and race against mac80211 free'ing >>>>>> a buffer. Will test that tomorrow if nothing else comes up creeping my >>>>>> priority queue. >>>>> >>>>> This code looks weird to me. ÂOne of the paprd branches >>>>> deletes the skb, the other doesn't appear to. ÂNeither >>>>> null out bf->bf_mpdu, which would appear to leave a dangling >>>>> pointer in at least the dev_kfree_skb_any() branch. >>>>> >>>>> ath_tx_complete frees it's skb in all cases, so another >>>>> bf->bf_mpdu dangling pointer issue. >>>>> >>>>> Maybe at the least we should null out bf->bf_mpdu when >>>>> skb is consumed? >>>> >>>> You're reading my mind, that was what I was going to test today. Still >>>> doing e-mail sweep though. >>> >>> At least in the xmit path, it seems cards that have EDMA support do >>> things a bit different. ÂOut of curiosity, on the system(s), you >>> reproduce >>> this, are any of yours supporting EDMA? ÂMine appear to not support EDMA. >> >> EDMA is used on>= AR9003 families by Atheros. And no, I am not >> testing with an EDMA card, I am testing with an AR9002 family card, >> the AR9280 card. I am going to disregard the TX stuff as the bug is an >> RX issue :) I was able to more easily reproduce by doing an skb_copy() >> and free'ing the buffer right afterwards on the ath_send_to_mac80211() >> thingy, So it does appear that the poison check just happens more >> often when we do an skb_copy(). One reason this is easy to reproduce >> with multiple STAs is mac80211 uses skb_copy() to process each >> received skb for each STA. >> >> In my tests so far, protecting the rxbuf list with spin_lock_irqsave() >> did not help, and the wmb(); didn't either, something else is going on >> here. It would be nice to hack slab to keep an entire trace of the >> place the buffer was last free'd at instead of just the caller that >> freed it. > > I instrumented slub a while back and got the backtrace. ÂIt > was always in the same place for my testing. > > Here's the slub patch if you are interested in using it yourself: > https://patchwork.kernel.org/patch/236921/ when compiling this patch I get: arch/x86/built-in.o: In function `store_stack': /home/mcgrof/wireless-testing/arch/x86/kernel/dumpstack.c:259: undefined reference to `store_trace' Luis -- 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
