From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir.fraser@eu.citrix.com>
Subject: Re: [Patch] avoid deadlock during console output
Date: Mon, 09 Mar 2009 08:28:13 +0000
Message-ID: <C5DA839D.47DC%keir.fraser@eu.citrix.com>
References: <49B4B4B1.9060505@fujitsu-siemens.com>
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To: Juergen Gross <juergen.gross@fujitsu-siemens.com>
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On 09/03/2009 06:18, "Juergen Gross" <juergen.gross@fujitsu-siemens.com>
wrote:

> Hmm, do you think your patch is okay?
> tasklet_schedule is taking another lock and uses BUG_ON then...
> I would suggest to modify tasklet_schedule:

I can live with the error patch of BUG_ON() not working in this one case. I
don't think releasing the lock suffices anyway, as we'll just end up in a
recursive loop until the hypervisor stack overflows. The BUG_ON() here is
more for informative code annotation than because it's at all likely to
fire.

It perhaps makes sense to disable the tasklet_schedule() based on a flag set
in console_force_unlock(). That would at least allow NMI-based watchdog to
print if we did ever hit the BUG_ON() deadlock (or any other crash while the
tasklet lock is held).

 -- Keir