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virtio_net: Fix recursive call to cpus_read_lock()

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[ Upstream commit de33212f768c5d9e2fe791b008cb26f92f0aa31c ]

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: 47be24796c ("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>
Link: https://lore.kernel.org/r/20201223025421.671-1-jdike@akamai.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jeff Dike 2020-12-22 21:54:21 -05:00 committed by Greg Kroah-Hartman
parent 087cfc7359
commit 23f8bea3e9
1 changed files with 7 additions and 5 deletions
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12
drivers/net/virtio_net.c
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@ -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) {
put_online_cpus();
goto err;
}
virtnet_set_affinity(vi);
put_online_cpus();
netif_set_real_num_tx_queues(dev, queue_pairs);
netif_set_real_num_rx_queues(dev, queue_pairs);
err:
return err;
}