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

Jörn Engel
2014-04-24T23:30:18Z

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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