Re: [PATCH] virtio_net: Fix recursive call to cpus_read_lock()
From: Jason Wang <jasowang@redhat.com>
Date: 2020-12-22 03:50:43
Also in:
virtualization
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 <redacted>
---Adding netdev. The patch can go with -net and is needed for -stable. Acked-by: Jason Wang <jasowang@redhat.com>
quoted hunk
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; }