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Re: [PATCH] Prevent netpoll hanging when link is down

To: Matt Mackall <mpm@xxxxxxxxxxx>
Subject: Re: [PATCH] Prevent netpoll hanging when link is down
From: Colin Leroy <colin@xxxxxxxxxx>
Date: Mon, 11 Oct 2004 22:45:42 +0200
Cc: Andi Kleen <ak@xxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxx>, netdev@xxxxxxxxxxx
In-reply-to: <20041011165851.GN31237@waste.org>
References: <20041007214505.GB31558@wotan.suse.de> <20041008090610.70d7e183@pirandello> <20041008220001.GE31237@waste.org> <20041008151839.01823e0c.akpm@osdl.org> <20041010205928.6e54df7e.davem@davemloft.net> <20041011154000.GB26350@wotan.suse.de> <20041011162224.GL31237@waste.org> <20041011163226.GG26350@wotan.suse.de> <20041011163601.GM31237@waste.org> <20041011164315.GH26350@wotan.suse.de> <20041011165851.GN31237@waste.org>
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On 11 Oct 2004 at 11h10, Matt Mackall wrote:

Hi, 

> Ergh, you deleted the context. Again, imagine we're originally in
> ->poll() for _a non-netpoll-related reason_. In other words, the
> console sem is not taken, because we're just doing routine network
> I/O. While in poll(), we take a private driver lock. Then for whatever
> reason, we printk -> netconsole -> netpoll -> poll() again where we
> attempt to retake the private driver lock.
> 
> > P.S.: I made the same mistake long ago, but akpm set me straight.
> 
> I'm pretty sure this case is different.

I tried replacing spin_lock by spin_trylock in poll() and a few other
functions (and returning accordingly), but it didn't help. I'm beginning
to think I won't be able to debug this one! ;)

-- 
Colin
  "When in doubt, do the right thing."

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