linux-kernel - Re: [RFC] net: napi fix

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Date:	Wed, 12 Dec 2007 12:29:23 -0500
From:	Andrew Gallatin <gallatin@...i.com>
To:	David Miller <davem@...emloft.net>
CC:	joonwpark81@...il.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, jgarzik@...ox.com,
	Stephen Hemminger <shemminger@...ux-foundation.org>
Subject: Re: [RFC] net: napi fix

[I apologize for loosing threading, I'm replying from the archives]

 > The problem is that the driver is doing a NAPI completion and
 > re-enabling chip interrupts with work_done == weight, and that is
 > illegal.

The only time at least myri10ge will do this is due to
the !netif_running(netdev) check.   Eg, from myri10ge's poll:

	work_done = myri10ge_clean_rx_done(mgp, budget);

	if (work_done < budget || !netif_running(netdev)) {
		netif_rx_complete(netdev, napi);
		put_be32(htonl(3), mgp->irq_claim);
	}

Is the netif_running() check even required? Is this just
a bad way to solve a race with running NAPI at down() time
that would be better solved by putting a napi_synchronize()
in the driver's down() routine?

I'd rather fix this right than add another check to a
questionable code path.

Thanks,

Drew
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