Re: [PATCH 1/3] printk: Fix kdb_trap_printk placement

[Petr Mladek]

Hi,

I thought about this a lot from several angles. And I would prefer
sligly different placement, see the patch below.

On Thu 2017-09-28 14:18:24, Peter Zijlstra wrote:
> Some people figured vprintk_emit() makes for a nice API and exported
> it, bypassing the kdb trap.

Sigh, printk() API is pretty complicated and this export
made it much worse. Well, there are two things:

First, kdb_trap_printk name is a bit misleading. It is not a
generic trap of any printk message. Instead it seems to be
used to redirect only particular messages from some existing
functions, e.g. show_regs() called from kdb_dumpregs().

Second, it seems that the only user of the exported vprintk_emit()
is dev_vprintk_emit(). I believe that code using this wrapper
is not called in the sections where kdb_trap_printk is incremented.

As a result, I think that we do not need to handle kdb_trap_printk
in vprintk_emit().


> This still leaves vprintk_nmi() outside of the kbd reach, should that
> be fixed too?

I think that it is safe after all, see the commit message in the patch
below.