Re: [PATCH 00/10] printk: Avoid deadlock in NMI + vprintk_emit() cleanup

[Jan Kara]

On Fri 29-05-15 13:50:45, Andrew Morton wrote:
> On Mon, 25 May 2015 14:46:23 +0200 Petr Mladek <pmladek@xxxxxxx> wrote:
> 
> > The main source of deadlocks caused by printk() in NMI context has been
> > solved by the commit a9edc88093287 ("x86/nmi: Perform a safe NMI stack
> > trace on all CPUs").
> > 
> > But there are still few warnings printed in the NMI code that could
> > case a deadlock. For example, see the freeze discussed at
> > https://lkml.org/lkml/2015/5/20/481
> 
> I'm not (yet) convinced that we want the entire patchset btw.  Do we
> really want to try to semi-support printk from NMI?  With a rather
> nasty set of hacks?
> 
> Why not just delete the offending printks?
  And what about WARN_ONs and BUG_ONs? Delete as well? Or just don't print
anything when we are in NMI? I agree that NMI is so problematic context
that restricting printk there makes some sence. OTOH propagating
information from NMI to user is useful as well so I'm somewhat undecided.

								Honza
-- 
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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