On 11/15/23 5:26 AM, Yoshihiro Shimoda wrote:
> Fix races between ravb_tx_timeout_work() and functions of net_device_ops
> and ethtool_ops by using rtnl_trylock() and rtnl_unlock(). Note that
> since ravb_close() is under the rtnl lock and calls cancel_work_sync(),
> ravb_tx_timeout_work() should calls rtnl_trylock(). Otherwise, a deadlock
> may happen in ravb_tx_timeout_work() like below:
>
> CPU0 CPU1
> ravb_tx_timeout()
> schedule_work()
> ...
> __dev_close_many()
> // Under rtnl lock
> ravb_close()
> cancel_work_sync()
> // Waiting
> ravb_tx_timeout_work()
> rtnl_lock()
> // This is possible to cause a deadlock
>
> And, if rtnl_trylock() fails and the netif is still running,
> rescheduling the work with 1 msec delayed. So, using
> schedule_delayed_work() instead of schedule_work().
>
> Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper")
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> Reviewed-by: Sergey Shtylyov <s.shtylyov@xxxxxx>
Hm, I haven't reviewed this version... :-)
> Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
[...]
> diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
> index e0f8276cffed..e9bb8ee3ba2d 100644
> --- a/drivers/net/ethernet/renesas/ravb.h
> +++ b/drivers/net/ethernet/renesas/ravb.h
> @@ -1081,7 +1081,7 @@ struct ravb_private {
> u32 cur_tx[NUM_TX_QUEUE];
> u32 dirty_tx[NUM_TX_QUEUE];
> struct napi_struct napi[NUM_RX_QUEUE];
> - struct work_struct work;
> + struct delayed_work work;
Not sure this is justified...
Then again, what do I know about workqueues? Not much... :-)
[...]
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index c70cff80cc99..ca7db8a5b412 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -1863,17 +1863,24 @@ static void ravb_tx_timeout(struct net_device *ndev, unsigned int txqueue)
> /* tx_errors count up */
> ndev->stats.tx_errors++;
>
> - schedule_work(&priv->work);
> + schedule_delayed_work(&priv->work, 0);
> }
>
> static void ravb_tx_timeout_work(struct work_struct *work)
> {
> - struct ravb_private *priv = container_of(work, struct ravb_private,
> + struct delayed_work *dwork = to_delayed_work(work);
> + struct ravb_private *priv = container_of(dwork, struct ravb_private,
> work);
> const struct ravb_hw_info *info = priv->info;
> struct net_device *ndev = priv->ndev;
> int error;
>
> + if (!rtnl_trylock()) {
> + if (netif_running(ndev))
> + schedule_delayed_work(&priv->work, msecs_to_jiffies(10));
The delay is rather arbitrary. Why not e.g. 1 ms?
[...]
MBR, Sergey
