Messages in this thread | | | Date | Fri, 6 Aug 2021 11:25:23 +0200 | From | Marc Kleine-Budde <> | Subject | Re: [RESEND PATCH 4/4] can: c_can: cache frames to operate as a true FIFO |
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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@libero.it
Marc
-- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | [unhandled content-type:application/pgp-signature] | |