[BUG] Revert 0b05e2d671c4 'powerpc/32: cacheable_memcpy becomes memcpy'

[Thomas Gleixner]

On Wed, 16 Sep 2015, Steven Rostedt wrote:
> On Wed, 16 Sep 2015 22:01:06 +0200 (CEST)
> Thomas Gleixner <tglx at linutronix.de> wrote:
> > So now I have to chase down that one:
> > 
> > [    0.230210] ftrace: allocating 16560 entries in 49 pages
> > [    0.273313] ------------[ cut here ]------------
> > [    0.278048] WARNING: at /home/tglx/work/kernel/tip/tip/kernel/trace/ftrace.c:1974
> 
> OK, so this is where ftrace converts the mcount to nops.
> 
> Just to be clear, there's nothing in the command line that enables any
> function tracing, is there?

Nothing on the command line.

> > Happens somewhere between the powerpc merge and rc1. System boots up
> > to userspace and then locks hard ....

Digging deeper. My assumption that it's a post powerpc merge failure
turned out to be wrong.

Some more data points. I see the above splat with

CONFIG_FUNCTION_TRACER=y
CONFIG_FUNCTION_GRAPH_TRACER=y

It goes away with 

CONFIG_FUNCTION_TRACER=y
CONFIG_FUNCTION_GRAPH_TRACER=n

But the box still does not get to the login prompt.

CONFIG_FUNCTION_TRACER=n

makes it work again.

It's not observable before the ppc merge, but I can't identify the
culprit by bisection. bisection led into lala land.

Thanks,

	tglx