On 2018/10/18 17:43, Sebastian Andrzej Siewior wrote:
> on 32bit, lockdep notices that virtnet_open() and refill_work() invoke
> try_fill_recv() from process context while virtnet_receive() invokes the
> same function from BH context. The problem that the seqcounter within
> u64_stats_update_begin() may deadlock if it is interrupted by BH and
> then acquired again.
>
> Introduce u64_stats_update_begin_bh() which disables BH on 32bit
> architectures. Since the BH might interrupt the worker, this new
> function should not limited to SMP like the others which are expected
> to be used in softirq.
>
> With this change we might lose increments but this is okay. The
> important part that the two 32bit parts of the 64bit counter are not
> corrupted.
>
> Fixes: 461f03dc99cf6 ("virtio_net: Add kick stats").
> Suggested-by: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
NACK. Again, this race should not happen because of NAPI guard.
We need to investigate why this warning happened.
--
Toshiaki Makita
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