virtio_net: use non-reentrant workqueue. (f1776dad) · Commits · 戴 / test

Michael S. Tsirkin also noticed that we could run the refill work multiple CPUs: if we kick off a refill on one CPU and then on another, they would both manipulate the queue at the same time (they use napi_disable to avoid racing against the receive handler itself). Tejun points out that this is what the WQ_NON_REENTRANT flag is for, and that there is a convenient system kthread we can use. Signed-off-by:

Rusty Russell <rusty@rustcorp.com.au> Signed-off-by:

David S. Miller <davem@davemloft.net>

drivers/net/virtio_net.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -508,7 +508,7 @@ static void refill_work(struct work_struct *work)
		/* In theory, this can happen: if we don't get any buffers in
		* we will never try to fill again. */
		if (still_empty)
		schedule_delayed_work(&vi->refill, HZ/2);
		queue_delayed_work(system_nrt_wq, &vi->refill, HZ/2);
		}

		static int virtnet_poll(struct napi_struct *napi, int budget)
		@@ -527,7 +527,7 @@ again:

		if (vi->num < vi->max / 2) {
		if (!try_fill_recv(vi, GFP_ATOMIC))
		schedule_delayed_work(&vi->refill, 0);
		queue_delayed_work(system_nrt_wq, &vi->refill, 0);
		}

		/* Out of packets? */
		@@ -729,7 +729,7 @@ static int virtnet_open(struct net_device *dev)

		/* Make sure we have some buffers: if oom use wq. */
		if (!try_fill_recv(vi, GFP_KERNEL))
		schedule_delayed_work(&vi->refill, 0);
		queue_delayed_work(system_nrt_wq, &vi->refill, 0);

		virtnet_napi_enable(vi);
		return 0;

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