linux-kernel - Re: printk: preempt_disable with long time resulting in softlockup/RCU stall issues

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Message-ID: <1436376929.2682.85.camel@perches.com>
Date:	Wed, 08 Jul 2015 10:35:29 -0700
From:	Joe Perches <joe@...ches.com>
To:	"Luis R. Rodriguez" <mcgrof@...e.com>
Cc:	Gavin Hu <gavin.hu.2010@...il.com>, Petr Mladek <pmladek@...e.com>,
	linux-kernel@...r.kernel.org, Alex Elder <elder@...aro.org>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	Peter Hurley <peter@...leysoftware.com>,
	Tejun Heo <tj@...nel.org>, cxie4@...vell.com, cldu@...vell.com,
	xjian@...vell.com, fswu@...vell.com, Jan Kara <jack@...e.cz>
Subject: Re: printk: preempt_disable with long time resulting in
 softlockup/RCU stall issues

On Wed, 2015-07-08 at 19:04 +0200, Luis R. Rodriguez wrote:
> On Wed, Jul 08, 2015 at 05:08:35PM +0800, Gavin Hu wrote:
> > Hi,
> > 
> > Yes. We should disable the printk_limit feature when panic to avoid missing
> > messages.
> 
> Sounds like you have been looking into it and have a good idea of what you
> want to do, why not try it and send some RFC patches ?
> 
> While at it, then we could consider doing different things depending on the
> message type. KERN_EMERG would disable preemption, whereas KERN_INFO may not be
> so critical to require it.

That might be a bit difficult to implement with complete correctness
given KERN_EMERG use and continuation lines.


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