On Wed, Jun 11, 2025 at 04:03:52AM -0700, Saurabh Singh Sengar wrote:
> On Wed, Jun 11, 2025 at 01:46:13AM -0700, Erni Sri Satya Vennela wrote:
> > When net_shaper_ops are enabled for MANA, netdev_ops_lock
> > becomes active.
> >
> > The netvsc sets up MANA VF via following call chain:
> >
> > netvsc_vf_setup()
> > dev_change_flags()
> > ...
> > __dev_open() OR __dev_close()
> >
> > dev_change_flags() holds the netdev mutex via netdev_lock_ops.
> >
> > During this process, mana_create_txq() and mana_create_rxq()
> > invoke netif_napi_add_tx(), netif_napi_add_weight(), and napi_enable(),
> > all of which attempt to acquire the same lock,
> > leading to a potential deadlock.
>
> commit message could be better oriented.
>
> >
> > Similarly, mana_destroy_txq() and mana_destroy_rxq() call
> > netif_napi_disable() and netif_napi_del(), which also contend
> > for the same lock.
> >
> > Switch to the _locked variants of these APIs to avoid deadlocks
> > when the netdev_ops_lock is held.
> >
> > Fixes: d4c22ec680c8 ("net: hold netdev instance lock during
> > ndo_open/ndo_stop")
> > Signed-off-by: Erni Sri Satya Vennela <er...@linux.microsoft.com>
> > Reviewed-by: Haiyang Zhang <haiya...@microsoft.com>
> > Reviewed-by: Shradha Gupta <shradhagu...@linux.microsoft.com>
> > ---
> > drivers/net/ethernet/microsoft/mana/mana_en.c | 39 ++++++++++++++-----
> > 1 file changed, 30 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c
> > b/drivers/net/ethernet/microsoft/mana/mana_en.c
> > index ccd2885c939e..3c879d8a39e3 100644
> > --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> > +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> > @@ -1911,8 +1911,13 @@ static void mana_destroy_txq(struct
> > mana_port_context *apc)
> > napi = &apc->tx_qp[i].tx_cq.napi;
> > if (apc->tx_qp[i].txq.napi_initialized) {
> > napi_synchronize(napi);
> > - napi_disable(napi);
> > - netif_napi_del(napi);
> > + if (netdev_need_ops_lock(napi->dev)) {
> > + napi_disable_locked(napi);
> > + netif_napi_del_locked(napi);
> > + } else {
> > + napi_disable(napi);
> > + netif_napi_del(napi);
> > + }
>
> Instead of using if-else, we can used netdev_lock_ops(), followed by *_locked
> api-s.
> Same for rest of the patch.
>
I later realized that what we actually need is:
if (!netdev_need_ops_lock(napi->dev))
netdev_lock(dev);
not
if (netdev_need_ops_lock(napi->dev))
netdev_lock(dev);
Hence, netdev_lock_ops() is not appropriate. Instead, netdev_lock_ops_to_full()
seems to be a better choice.
> Reviewed-by: Saurabh Sengar <ssen...@linux.microsoft.com>
>
> - Saurabh
>
