On 05.08.2021 22:16:06, Dario Binacchi wrote:
> > > --- a/drivers/net/can/c_can/c_can.h
> > > +++ b/drivers/net/can/c_can/c_can.h
> > > @@ -200,6 +200,7 @@ struct c_can_priv {
> > > atomic_t sie_pending;
> > > unsigned long tx_dir;
> > > int last_status;
> > > + spinlock_t tx_lock;
> >
> > What does the spin lock protect?
[...]
> > > @@ -483,7 +469,11 @@ static netdev_tx_t c_can_start_xmit(struct sk_buff *skb,
> > > if (c_can_get_tx_free(tx_ring) == 0)
> > > netif_stop_queue(dev);
> > >
> > > - obj = idx + priv->msg_obj_tx_first;
> > > + spin_lock_bh(&priv->tx_lock);
> >
> > What does the spin_lock protect? The ndo_start_xmit function is properly
> > serialized by the networking core.
> >
>
> The spin_lock protects the access to the IF_TX interface.
How? You only use the spin_lock in c_can_start_xmit(), but not anywhere
else.
> Enabling the transmission of cached messages occur inside interrupt
The call chain is c_can_poll() -> c_can_do_tx(), and c_can_poll() is
called from NAPI, which is not the IRQ handler.
> and the use of the IF_RX interface, which would avoid the use of the
> spinlock, has not been validated by the tests.
What do you mean be has not been validated?
The driver already uses IF_RX to avoid concurrent access in
c_can_do_tx() for c_can_inval_tx_object() [1], why not use IF_RX for
c_can_object_put(), too?
[1] https://lore.kernel.org/r/20210302215435.18286-4-dariobin@xxxxxxxxx
Marc
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Pengutronix e.K. | Marc Kleine-Budde |
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