Re: [Ksummit-discuss] [TECH TOPIC] printk redesign

[Mauro Carvalho Chehab <mchehab@s-opensource.com>]

Em Mon, 19 Jun 2017 12:26:51 -0400
Steven Rostedt <rostedt@goodmis.org> escreveu:

> On Mon, 19 Jun 2017 17:20:55 +0200
> Andrew Lunn <andrew@lunn.ch> wrote:
> 
> 
> > > 4) All other kernel information that's not critical at all, and perhaps
> > > doesn't even need to be serialized. At least, not against the above.
> > > This could be cached, and outputted at a later time than when the
> > > printk() was called.    
> > 
> > Developers machine probably have different requirements to production
> > machines. When debugging during code development, i want the debug
> > output to be in the correct order, independent of the level. If you
> > are going to cause reordering, you might want to add a sequence number
> > to each output, so it is possible to put it back into the correct
> > order. And it needs to be clear when output is out of order.  

Even for developers, ensuring the correct order is a must.

If someone reports me a bug that the Kernel crashed because of some
driver, I would ask him to enable debug messages and send the crash
logs with it enabled. 

> Perhaps a kernel command line option could force this.

I'd say that a Kconfig option can also be used for that. In
the case of media, we have a config option that enables extra
debugging features (CONFIG_VIDEO_ADV_DEBUG). It seems that other
subsystems have similar things:

	$ grep ADV .config|grep DEB
	CONFIG_PM_ADVANCED_DEBUG=y
	CONFIG_BATMAN_ADV_DEBUGFS=y
	CONFIG_BATMAN_ADV_DEBUG=y
	CONFIG_VIDEO_ADV_DEBUG=y

Well, if any of such options are selected, I'd say that ordering
the logs should be the default.

Thanks,
Mauro