Re: [PATCH V2] virtio-net: fix the race between refill work and close
From: Jakub Kicinski <kuba@kernel.org>
Date: 2022-06-30 02:51:34
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On Thu, 30 Jun 2022 10:08:04 +0800 Jason Wang wrote:
quoted hunk ↗ jump to hunk
+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.