Re: [RFC] printk/sysrq: Don't play with console_loglevel

[Sergey Senozhatsky]

On (06/06/19 09:10), Petr Mladek wrote:
> > > > > > Provide KERN_UNSUPPRESSED printk() annotation for such legacy places.
> > > > > > Make sysrq print the headers unsuppressed instead of changing
> > > > > > console_loglevel.
> > > 
> > > I like this idea. console_loglevel is temporary manipulated only
> > > when some messages should or should never appear on the console.
> > > Storing this information in the message flags would help
> > > to solve all the related races.
> > 
> > I don't really like the whole system-wide console_loglevel manipulation
> > thing,
> 
> Just to be sure. I wanted to say that I like the idea with
> KERN_UNSUPRESSED. So, I think that we are on the same page.

I understand. All I wanted to say is that KERN_UNSUPRESSED is
per-message, while the most interesting (and actually broken)
cases, IMHO, are per-context, IOW things like this one

	console_loglevel = NEW
	foo()
	  dump_stack()
	     printk
	     ...
	     printk
	console_loglevel = OLD

KERN_UNSUPRESSED does not help here. We probably can't convert
dump_stack() to KERN_UNSUPRESSED.

[..]
> Now, KERN_EMERG might alarm some monitor of console output. It might
> trigger unwanted reaction (forced reboot?) of the monitoring system
> even when sysrq was not called in emergency situation.
> 
> I am sure that we need to care about such monitors. I have to
> think more about it.

Sure.

	-ss