Re: [PATCH] ARM: ftrace: Ensure code modifications are synchronisedacross all cpus

From: Steven Rostedt
Date: Fri Dec 07 2012 - 10:28:47 EST

On Fri, 2012-12-07 at 14:55 +0000, Jon Medhurst (Tixy) wrote:
> > But also realize that function tracing is special :-) We have no cases
> > like this. The instruction being replaced is a call to mcount. In fact,
> > we replace it at boot with a nop. And this method only replaces that nop
> > into a call to function tracer, or replaces the call to function tracer
> > back to a nop. Always at the start of the function, and never involved
> > with conditionals. This limitation that function tracing imposes on what
> > we replace makes things a bit more sane in how we replace it.
> Then perhaps the method you suggest will work on ARM :-). However, that
> is not something I personally propose to implement at this time. (I was
> doing my good Samaritan act by trying to fix the crashes which another
> team was getting when trying to use ftrace.)

I'm not NACKing your previous patch, I was just suggesting to bring ARM
up to the future :-)

I have no problems with the patch, but I just want to put it out there
that there's better ways. It's part of the remove stomp_machine()
crusade ;-)

-- Steve

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