tree 7ed61aa920207a95b8f1bbcfb89d6623f0336e37
parent f91d718156fe93d0cf684cacf5f247c35a825d79
author Benjamin Poirier <bpoirier@suse.com> 1478512676 +0800
committer David S. Miller <davem@davemloft.net> 1478716270 -0500

bna: Add synchronization for tx ring.

We received two reports of BUG_ON in bnad_txcmpl_process() where
hw_consumer_index appeared to be ahead of producer_index. Out of order
write/read of these variables could explain these reports.

bnad_start_xmit(), as a producer of tx descriptors, has a few memory
barriers sprinkled around writes to producer_index and the device's
doorbell but they're not paired with anything in bnad_txcmpl_process(), a
consumer.

Since we are synchronizing with a device, we must use mandatory barriers,
not smp_*. Also, I didn't see the purpose of the last smp_mb() in
bnad_start_xmit().

Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>