Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

[Linus Torvalds]

On Wed, Apr 4, 2018 at 10:13 AM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> Something like this will even prevent modules from disabling the printk
> hash...

That still seems broken.

The *natural* thing to do would seem to be to tie the hash to the
printk state, kind of like the percpu buffers that safe_printk() and
friends use.

Modifying the hash global is fundamentally broken, since some problem
that happens *during* tracing - on another CPU entirely - would now
have the hashing disabled.

So at the *very* least this would need to be percpu logic, but even
that is honestly broken since an NMI might come in and want to printk
too.

Why don't you just use %px? That avoids all of these hacks.

So NAK on this stupid "enable and disable hashing that is
fundamentally broken" approach.

                     Linus