linux-kernel - Re: [PATCH] printk: Print cpu number along with time

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Message-ID: <alpine.LNX.2.00.1404250020370.8903@pobox.suse.cz>
Date:	Fri, 25 Apr 2014 00:21:20 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	David Rientjes <rientjes@...gle.com>
cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jörn Engel <joern@...fs.org>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org,
	peterz@...radead.org, akpm@...ux-foundation.org, cxie@...hat.com,
	Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH] printk: Print cpu number along with time

On Thu, 24 Apr 2014, David Rientjes wrote:

> > Well, if you have dmesg dump from panic that happens every other year, and 
> > you have to do post-mortem analysis on it, I am pretty sure you would love 
> > to be able to figure out how the stack traces would look like without 
> > inter-CPU interleaving. And I am pretty sure you wouldn't want to 
> > insert/enable a tracepoint and wait another two years for the bug to 
> > trigger again.
> 
> Sounds like the appropriate fix would be to serialize stack dumping to the 
> kernel log.

That's rather difficult, as it can be done both from NMI and non-NMI 
contexts, and those are very hard to synchronize.

-- 
Jiri Kosina
SUSE Labs
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