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From: Arnd Bergmann <arnd@arndb.de>
To: LABBE Corentin <clabbe.montjoie@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org, robh+dt@kernel.org,
	mark.rutland@arm.com, maxime.ripard@free-electrons.com,
	wens@csie.org, linux@armlinux.org.uk, davem@davemloft.net,
	devicetree@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com
Subject: Re: [PATCH v2 1/5] ethernet: add sun8i-emac driver
Date: Fri, 29 Jul 2016 11:26:57 +0200	[thread overview]
Message-ID: <4552489.XcKoxjnXeP@wuerfel> (raw)
In-Reply-To: <20160728131826.GA7582@Red>

On Thursday, July 28, 2016 3:18:26 PM CEST LABBE Corentin wrote:
> 
> I will reworked locking and it seems that no locking is necessary.
> I have added the following comment about the locking strategy:
> 
> /* Locking strategy:
>  * RX queue does not need any lock since only sun8i_emac_poll() access it.
>  * (All other RX modifiers (ringparam/ndo_stop) disable NAPI and so sun8i_emac_poll())
>  * TX queue is handled by sun8i_emac_xmit(), sun8i_emac_complete_xmit() and sun8i_emac_tx_timeout()
>  * (All other RX modifiers (ringparam/ndo_stop) disable NAPI and stop queue)
>  *
>  * sun8i_emac_xmit() could fire only once (netif_tx_lock)
>  * sun8i_emac_complete_xmit() could fire only once (called from NAPI)
>  * sun8i_emac_tx_timeout() could fire only once (netif_tx_lock) and couldnt
>  * race with sun8i_emac_xmit (due to netif_tx_lock) and with sun8i_emac_complete_xmit which disable NAPI.
>  *
>  * So only sun8i_emac_xmit and sun8i_emac_complete_xmit could fire at the same time.
>  * But they never could modify the same descriptors:
>  * - sun8i_emac_complete_xmit() will modify only descriptors with empty status
>  * - sun8i_emac_xmit() will modify only descriptors set to DCLEAN
>  * Proper memory barriers ensure that descriptor set to DCLEAN could not be
>  * modified latter by sun8i_emac_complete_xmit().
>  * */

Sounds good, the comment is certainly very helpful here.

	Arnd

  reply	other threads:[~2016-07-29  9:27 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-20  8:03 [PATCH v2 0/5] net-next: ethernet: add sun8i-emac driver LABBE Corentin
2016-07-20  8:03 ` [PATCH v2 1/5] " LABBE Corentin
2016-07-20  9:56   ` Arnd Bergmann
2016-07-28 13:18     ` LABBE Corentin
2016-07-29  9:26       ` Arnd Bergmann [this message]
2016-07-25 19:54   ` Maxime Ripard
2016-07-28 14:57     ` LABBE Corentin
2016-07-29 17:25       ` Maxime Ripard
2016-07-30  1:30         ` Chen-Yu Tsai
2016-07-30  7:34           ` Maxime Ripard
2016-07-29 10:12     ` Andre Przywara
2016-08-24 12:02     ` LABBE Corentin
2016-08-26 20:49       ` Maxime Ripard
2016-07-20  8:03 ` [PATCH v2 2/5] MAINTAINERS: Add myself as maintainers of sun8i-emac LABBE Corentin
2016-07-20  8:03 ` [PATCH v2 3/5] ARM: sun8i: dt: Add DT bindings documentation for Allwinner sun8i-emac LABBE Corentin
2016-07-20 19:15   ` Rob Herring
2016-07-28 13:21     ` LABBE Corentin
2016-07-21  7:55   ` Maxime Ripard
2016-07-28 13:40     ` LABBE Corentin
2016-07-28 18:49       ` Maxime Ripard
2016-07-29  8:15         ` LABBE Corentin
2016-07-29 18:12           ` Maxime Ripard
2016-07-20  8:03 ` [PATCH v2 4/5] ARM: dts: sun8i-h3: add sun8i-emac ethernet driver LABBE Corentin
2016-07-20  8:03 ` [PATCH v2 5/5] ARM: dts: sun8i: Enable sun8i-emac on the Orange PI PC LABBE Corentin
2016-07-25 13:16 ` [PATCH v2 0/5] net-next: ethernet: add sun8i-emac driver paulo

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