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Date: Wed, 29 Jun 2022 19:51:23 -0700 From: Jakub Kicinski <kuba@...nel.org> To: Jason Wang <jasowang@...hat.com> Cc: mst@...hat.com, davem@...emloft.net, virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH V2] virtio-net: fix the race between refill work and close On Thu, 30 Jun 2022 10:08:04 +0800 Jason Wang wrote: > +static void enable_refill_work(struct virtnet_info *vi) > +{ > + spin_lock(&vi->refill_lock); > + vi->refill_work_enabled = true; > + spin_unlock(&vi->refill_lock); > +} > + > +static void disable_refill_work(struct virtnet_info *vi) > +{ > + spin_lock(&vi->refill_lock); > + vi->refill_work_enabled = false; > + spin_unlock(&vi->refill_lock); > +} > + > static void virtqueue_napi_schedule(struct napi_struct *napi, > struct virtqueue *vq) > { > @@ -1527,8 +1547,12 @@ static int virtnet_receive(struct receive_queue *rq, int budget, > } > > if (rq->vq->num_free > min((unsigned int)budget, virtqueue_get_vring_size(rq->vq)) / 2) { > - if (!try_fill_recv(vi, rq, GFP_ATOMIC)) > - schedule_delayed_work(&vi->refill, 0); > + if (!try_fill_recv(vi, rq, GFP_ATOMIC)) { > + spin_lock(&vi->refill_lock); > + if (vi->refill_work_enabled) > + schedule_delayed_work(&vi->refill, 0); > + spin_unlock(&vi->refill_lock); Are you sure you can use the basic spin_lock() flavor in all cases? Isn't the disable/enable called from a different context than this thing here? The entire delayed work construct seems a little risky because the work may go to sleep after disabling napi, causing large latency spikes. I guess you must have a good reason no to simply reschedule the NAPI and keep retrying with GFP_ATOMIC... Please add the target tree name to the subject.
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