On 2020/12/22 上午11:36, 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.
Signed-off-by: Jeff Dike <jdike@xxxxxxxxxx>
---
Adding netdev.
The patch can go with -net and is needed for -stable.
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
drivers/net/virtio_net.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
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){
+ 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;
}
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