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Date: Thu, 18 Oct 2018 18:06:57 +0900 From: Toshiaki Makita <makita.toshiaki@....ntt.co.jp> To: Sebastian Andrzej Siewior <bigeasy@...utronix.de> Cc: Stephen Hemminger <stephen@...workplumber.org>, netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org, tglx@...utronix.de, "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, "David S. Miller" <davem@...emloft.net> Subject: Re: [PATCH] virtio_net: add local_bh_disable() around u64_stats_update_begin 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@...workplumber.org> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de> 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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