On 10/12/2010 10:31 PM, Vasanthakumar Thiagarajan wrote:
On Wed, Oct 13, 2010 at 12:05:53AM +0530, Ben Greear wrote:
On 10/11/2010 11:10 PM, Luis R. Rodriguez wrote:
On Mon, Oct 11, 2010 at 8:27 PM, Ben Greear<greearb@xxxxxxxxxxxxxxx> wrote:
Another thing I was thinking about: Maybe the queue of skbs and dma
addresses
in ath9k is getting corrupted by multiple VIFs trying to write at once?
Maybe
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. One of the paprd branches
deletes the skb, the other doesn't appear to. Neither
null out bf->bf_mpdu, which would appear to leave a dangling
pointer in at least the dev_kfree_skb_any() branch.
Single skb is (re)used for sending paprd training frames on more
than one chains. This skb needs to be freed only when paprd fails on
any of the chains or it succeeded on all the chains. The failure
case is handled in ath_tx_complete_buf() and success case is in
ath_paprd_calibrate().
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?
I dont see any point in NULLing out bf->bf_mpdu. bf is
reclaimed onto a free tx buf pool as soon as it is done
with the skb. bf_mpdu of any of the bf's is never accessed
without any initialization (bf_ampdu = skb).
The code can use skb after its deleted currently, because
ath_debug_stat_tx(sc, txq, bf, ts); references the bf_ampdu
object (I think I added that reference lately..so it's really
a bug that I caused). At the least, we should move the ath_debug_stat_tx
logic before the ath_tx_complete() call.
As for the paprd path, it looks racy to me: What if the paprd timer
expires while the ath_tx_complete_buf logic is running?
Either way, it seems safer to null out the bf_ampdu field after
the memory is consumed..it could prevent some tricky bugs later.
Thanks,
Ben
--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc http://www.candelatech.com
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