linux-kernel - Re: [PATCH 1/2 V2] kaweth: Fix locking to be SMP-safe

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Date:	Tue, 31 Mar 2009 15:10:28 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	oliver@...kum.org
Cc:	Larry.Finger@...inger.net, jgarzik@...ox.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 1/2 V2] kaweth: Fix locking to be SMP-safe

From: Oliver Neukum <oliver@...kum.org>
Date: Wed, 1 Apr 2009 00:13:04 +0200

> Am Dienstag 31 März 2009 20:45:49 schrieb Larry Finger:
> 
> > @@ -796,7 +799,7 @@ static int kaweth_start_xmit(struct sk_b
> 
> > @@ -848,7 +851,7 @@ skip:
> >  		net->trans_start = jiffies;
> >  	}
> >
> > -	spin_unlock(&kaweth->device_lock);
> > +	spin_unlock_irq(&kaweth->device_lock);
> 
> Here you enable interrupts. Are you sure ndo_start_xmit is never
> called with interrupts disabled?

It must never be invoked that way, this would break so many
drivers.

On the other hand, all of these driver paths never execute
in a real hardware interrupt context, the deepest it gets
into is software interrupts.  So spin_*lock*_bh() might be
more appropriate.
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