On Tue, 22 Dec 2020 21:54:21 -0500 Jeff Dike wrote:
virtnet_set_channels can recursively call cpus_read_lock if CONFIG_XPS and CONFIG_HOTPLUG are enabled.
The path is: virtnet_set_channels - calls get_online_cpus(), which is a trivial wrapper around cpus_read_lock() netif_set_real_num_tx_queues netif_reset_xps_queues_gt netif_reset_xps_queues - calls cpus_read_lock()
This call chain and potential deadlock happens when the number of TX queues is reduced.
This commit the removes netif_set_real_num_[tr]x_queues calls from inside the get/put_online_cpus section, as they don't require that it be held.
Fixes: 47be24796c13 ("virtio-net: fix the set affinity bug when CPU IDs are not consecutive")
Signed-off-by: Jeff Dike jdike@akamai.com Acked-by: Jason Wang jasowang@redhat.com Acked-by: Michael S. Tsirkin mst@redhat.com Cc: stable@vger.kernel.org
Queued for stable.
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 052975ea0af4..e02c7e0f1cf9 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -2093,14 +2093,16 @@ static int virtnet_set_channels(struct net_device *dev, get_online_cpus(); err = _virtnet_set_queues(vi, queue_pairs);
- if (!err) {
netif_set_real_num_tx_queues(dev, queue_pairs);netif_set_real_num_rx_queues(dev, queue_pairs);virtnet_set_affinity(vi);
- if (err){
Added missing space here.
put_online_cpus();goto err;
And applied, thanks!