netdev - Re: [PATCH] bcm63xx_enet: fix poll callback.

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Date:	Tue, 03 Mar 2015 05:29:59 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Nicolas Schichan <nschichan@...ebox.fr>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Tobias Klauser <tklauser@...tanz.ch>,
	Felipe Balbi <balbi@...com>,
	Wilfried Klaebe <w-lkml@...enslange-mailadresse.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexander Duyck <alexander.h.duyck@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bcm63xx_enet: fix poll callback.

On Tue, 2015-03-03 at 12:45 +0100, Nicolas Schichan wrote:
> In case there was some tx buffer reclaimed and not enough rx packets
> to consume the whole budget, napi_complete would not be called and
> interrupts would be kept disabled, effectively resulting in the
> network core never to call the poll callback again and no rx/tx
> interrupts to be fired either.
> 
> Fix that by only accounting the rx work done in the poll callback.
> 
> Signed-off-by: Nicolas Schichan <nschichan@...ebox.fr>
> ---

This looks better, thanks.

Acked-by: Eric Dumazet <edumazet@...gle.com>

Note that the way bcm_enet_tx_reclaim() is written, it can livelock on
SMP hosts :

CPU 1,2,3,...  keep queuing packets via ndo_start_xmit()

CPU 0 is looping forever in bcm_enet_tx_reclaim() draining queue and
freeing skbs.

To avoid that, I would take priv->tx_lock only once, or add a limit on
the number of skbs that can be drained per round.


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