From: Dario Binacchi <dariobin@libero.it> To: Marc Kleine-Budde <mkl@pengutronix.de> Cc: linux-kernel@vger.kernel.org, Gianluca Falavigna <gianluca.falavigna@inwind.it>, Andrew Lunn <andrew@lunn.ch>, "David S. Miller" <davem@davemloft.net>, Jakub Kicinski <kuba@kernel.org>, Oliver Hartkopp <socketcan@hartkopp.net>, Vincent Mailhol <mailhol.vincent@wanadoo.fr>, Wolfgang Grandegger <wg@grandegger.com>, linux-can@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [RESEND PATCH 4/4] can: c_can: cache frames to operate as a true FIFO Date: Sat, 7 Aug 2021 14:36:15 +0200 (CEST) [thread overview] Message-ID: <1265712151.254355.1628339776021@mail1.libero.it> (raw) In-Reply-To: <20210806092523.hij5ejjq6wecbgfr@pengutronix.de> > Il 06/08/2021 11:25 Marc Kleine-Budde <mkl@pengutronix.de> ha scritto: > > > 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? It's been a while since I submitted the series and I certainly got confused. > > 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 Right! Thanks and Regards, Dario > > 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 |
prev parent reply other threads:[~2021-08-07 12:40 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-25 16:11 [RESEND PATCH 0/4] " Dario Binacchi 2021-07-25 16:11 ` [RESEND PATCH 1/4] can: c_can: remove struct c_can_priv::priv field Dario Binacchi 2021-07-25 16:11 ` [RESEND PATCH 2/4] can: c_can: exit c_can_do_tx() early if no frames have been sent Dario Binacchi 2021-07-25 16:11 ` [RESEND PATCH 3/4] can: c_can: support tx ring algorithm Dario Binacchi 2021-08-04 9:37 ` Marc Kleine-Budde 2021-07-25 16:11 ` [RESEND PATCH 4/4] can: c_can: cache frames to operate as a true FIFO Dario Binacchi 2021-08-04 9:34 ` Marc Kleine-Budde 2021-08-05 20:12 ` Dario Binacchi 2021-08-06 7:52 ` Marc Kleine-Budde 2021-08-04 9:45 ` Marc Kleine-Budde 2021-08-05 20:16 ` Dario Binacchi 2021-08-06 9:25 ` Marc Kleine-Budde 2021-08-07 12:36 ` Dario Binacchi [this message]
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