netdev - Re: [PATCH] Fix deadlock between boomerang_interrupt and boomerang_start

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Message-ID: <20100811175130.GC23317@hmsreliant.think-freely.org>
Date:	Wed, 11 Aug 2010 13:51:30 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] Fix deadlock between boomerang_interrupt and
 boomerang_start_tx in 3c59x

On Wed, Aug 11, 2010 at 12:09:00PM -0400, Stephen Hemminger wrote:
> On Wed, 11 Aug 2010 11:12:57 -0400
> Neil Horman <nhorman@...driver.com> wrote:
> 
> > If netconsole is in use, there is a possibility for deadlock in 3c59x between
> > boomerang_interrupt and boomerang_start_xmit.  Both routines take the vp->lock,
> > and if netconsole is in use, a pr_* call from the boomerang_interrupt routine
> > will result in the netconsole code attempting to trnasmit an skb, which can try
> > to take the same spin lock, resulting in de
> 
> I thought we agreed that any device supporting netconsole agrees
> to not call printk in the transmit path. Just kill the pr_* call.
> 

3c59x isn't calling pr_* in the transmit path, its calling it in the interrupt
handler, but since the interrupt handler and the transmit path share a spinlock,
you get a deadlock in that case.  We could kill the several pr_debug calls in
the interrupt path, but I don't think thats really needed in this case.

Neil

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