Re: [PATCH] printk/tracing: Do not trace printk_nmi_enter()

[Sergey Senozhatsky]

On (09/07/18 16:03), Peter Zijlstra wrote:
> > 
> > I would even argue that placing printk_nmi_enter() between
> > lockdep_off() and ftrace_nmi_enter() is wrong because if in the future
> > printk_nmi_enter() were to do any ftrace tracing, it wont be caught, as
> > it was by having it before lockdep_off().
> > 
> > printk_nmi_enter() should not muck with IRQ state, nor should it do any
> > ftrace tracing. Since ftrace mucks with IRQ state when it gets enabled
> > or disabled, it will screw up lockdep, and lockdep will complain. That
> > way we can use lockdep not being off to catch this bug.
> 
> The very bestest solution is to rm -rf printk ;-)

Talented, capable and tremendously clever people had spent decades on
making printk what it is today. I feel responsible for respecting that
effort and, thus, my vote would be to keep printk around for a while.
... we also support !CONFIG_PRINTK builds ;)

	-ss