netdev - Re: [PATCH RFC] gianfar: Make polling safe with IRQs disabled

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Message-Id: <20091108.010533.212571001.davem@davemloft.net>
Date:	Sun, 08 Nov 2009 01:05:33 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	avorontsov@...mvista.com
Cc:	afleming@...escale.com, jason.wessel@...driver.com,
	netdev@...r.kernel.org, linuxppc-dev@...abs.org
Subject: Re: [PATCH RFC] gianfar: Make polling safe with IRQs disabled

From: Anton Vorontsov <avorontsov@...mvista.com>
Date: Thu, 5 Nov 2009 01:57:11 +0300

> When using KGDBoE, gianfar driver spits 'Interrupt problem' messages,
> which appears to be a legitimate warning, i.e. we may end up calling
> netif_receive_skb() or vlan_hwaccel_receive_skb() with IRQs disabled.
> 
> This patch reworks the RX path so that if netpoll is enabled (the
> only case when the driver don't know from what context the polling
> may be called), we check whether IRQs are disabled, and if so we
> fall back to safe variants of skb receiving functions.
> 
> Signed-off-by: Anton Vorontsov <avorontsov@...mvista.com>

This is bogus, I'll tell you why.

When you go into netif_receive_skb() we have a special check,
"if (netpoll_receive_skb(..." that takes care of all of the
details concerning doing a ->poll() from IRQ disabled context
via netpoll.

So this code you're adding should not be necessary.

Or, explain to me why no other driver needs special logic in their
->poll() handler like this and does not run into any kinds of netpoll
problems :-)
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