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

["Jörn Engel" <joern@logfs.org>]

On Fri, 25 April 2014 00:21:20 +0200, Jiri Kosina wrote:
> 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.

It is also easy to get wrong and cause a panic() that doesn't reboot
but instead gets stuck somewhere.

Plus, you might want similar serialization for other multi-line debug
messages.  Scsi error messages come to mind, but we have many more
examples.

Jörn

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