Commit d072218f authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by David S. Miller

hv_netvsc: avoid deadlocks between rtnl lock and vf_use_cnt wait

Here is a deadlock scenario:
- netvsc_vf_up() schedules netvsc_notify_peers() work and quits.
- netvsc_vf_down() runs before netvsc_notify_peers() gets executed. As it
  is being executed from netdev notifier chain we hold rtnl lock when we
  get here.
- we enter while (atomic_read(&net_device_ctx->vf_use_cnt) != 0) loop and
  wait till netvsc_notify_peers() drops vf_use_cnt.
- netvsc_notify_peers() starts on some other CPU but netdev_notify_peers()
  will hang on rtnl_lock().
- deadlock!

Instead of introducing additional synchronization I suggest we drop
gwrk.dwrk completely and call NETDEV_NOTIFY_PEERS directly. As we're
acting under rtnl lock this is legitimate.
Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Acked-by: default avatarHaiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f9a7da91
......@@ -644,12 +644,6 @@ struct netvsc_reconfig {
u32 event;
};
struct garp_wrk {
struct work_struct dwrk;
struct net_device *netdev;
struct net_device_context *net_device_ctx;
};
/* The context of the netvsc device */
struct net_device_context {
/* point back to our device context */
......@@ -667,7 +661,6 @@ struct net_device_context {
struct work_struct work;
u32 msg_enable; /* debug level */
struct garp_wrk gwrk;
struct netvsc_stats __percpu *tx_stats;
struct netvsc_stats __percpu *rx_stats;
......
......@@ -1151,17 +1151,6 @@ static void netvsc_free_netdev(struct net_device *netdev)
free_netdev(netdev);
}
static void netvsc_notify_peers(struct work_struct *wrk)
{
struct garp_wrk *gwrk;
gwrk = container_of(wrk, struct garp_wrk, dwrk);
netdev_notify_peers(gwrk->netdev);
atomic_dec(&gwrk->net_device_ctx->vf_use_cnt);
}
static struct net_device *get_netvsc_net_device(char *mac)
{
struct net_device *dev, *found = NULL;
......@@ -1253,15 +1242,8 @@ static int netvsc_vf_up(struct net_device *vf_netdev)
netif_carrier_off(ndev);
/*
* Now notify peers. We are scheduling work to
* notify peers; take a reference to prevent
* the VF interface from vanishing.
*/
atomic_inc(&net_device_ctx->vf_use_cnt);
net_device_ctx->gwrk.netdev = vf_netdev;
net_device_ctx->gwrk.net_device_ctx = net_device_ctx;
schedule_work(&net_device_ctx->gwrk.dwrk);
/* Now notify peers through VF device. */
call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, vf_netdev);
return NOTIFY_OK;
}
......@@ -1300,13 +1282,9 @@ static int netvsc_vf_down(struct net_device *vf_netdev)
netdev_info(ndev, "Data path switched from VF: %s\n", vf_netdev->name);
rndis_filter_close(netvsc_dev);
netif_carrier_on(ndev);
/*
* Notify peers.
*/
atomic_inc(&net_device_ctx->vf_use_cnt);
net_device_ctx->gwrk.netdev = ndev;
net_device_ctx->gwrk.net_device_ctx = net_device_ctx;
schedule_work(&net_device_ctx->gwrk.dwrk);
/* Now notify peers through netvsc device. */
call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, ndev);
return NOTIFY_OK;
}
......@@ -1378,7 +1356,6 @@ static int netvsc_probe(struct hv_device *dev,
INIT_DELAYED_WORK(&net_device_ctx->dwork, netvsc_link_change);
INIT_WORK(&net_device_ctx->work, do_set_multicast);
INIT_WORK(&net_device_ctx->gwrk.dwrk, netvsc_notify_peers);
spin_lock_init(&net_device_ctx->lock);
INIT_LIST_HEAD(&net_device_ctx->reconfig_events);
......
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