linux-kernel - Re: rmmod e1000 hangs (Was Re: 2.6.22-rc2-mm1)

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Message-ID: <20070525125413.GA29433@gondor.apana.org.au>
Date:	Fri, 25 May 2007 22:54:13 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"Kok, Auke" <auke-jan.h.kok@...el.com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: rmmod e1000 hangs (Was Re: 2.6.22-rc2-mm1)

On Thu, May 24, 2007 at 07:44:29AM -0700, Kok, Auke wrote:
>
> I get the feeling that a recent change exposed us to this, our lab has been 
> seeing similar OOPS's yesterday out of nothing.

Yep you're right.  It was the change where we removed the
netif_poll_enable call from e1000_open.  The problem is that
e1000_close calls e1000_down which in turn calls netif_poll_disable.
That means the next e1000_open won't reenable polling and the
dev_close (or in fact any call to netif_poll_disable) after that
will hang.

In fact my original premise is completely wrong since netif_poll_enable
can be safely called from dev_open *if* you can guarantee that no polls
have already been scheduled.

This should be the case as long as we keep IRQs disabled before
netif_poll_enable.  So the problem is that somehow we're getting
into e1000_open with IRQs enabled on the NIC which then causes a
poll to be scheduled before the call to netif_poll_enable.

So please revert my patch.

We need to find out why we're getting IRQs before calling
e1000_irq_enable in e1000_open.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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