On Wed, 16 Sep 2015, Steven Rostedt wrote:

On Wed, 16 Sep 2015 22:01:06 +0200 (CEST)
Thomas Gleixner [off-list ref] wrote:

quoted

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.

quoted

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