On Mon 2016-02-08 10:49:28, Steven Rostedt wrote:

On Mon, 8 Feb 2016 16:23:06 +0100
Petr Mladek [off-list ref] wrote:

quoted

quoted

From 2b0fcb678d7720d03f9c9f233b61ed9ed4d420b3 Mon Sep 17 00:00:00 2001  

From: Petr Mladek <pmladek@suse.com>
Date: Mon, 8 Feb 2016 16:03:03 +0100
Subject: [PATCH] ftrace: Allow to explicitly disable the build of the dynamic
 ftrace with regs

This patch allows to explicitly disable
CONFIG_DYNAMIC_FTRACE_WITH_REGS. We will need to do so on
PPC with a broken gcc. This situation will be detected at
buildtime and could not be handled by Kbuild automatically.

Wait. Can it be detected at build time? That is, does it cause a build
error? If so, then you can have Kbuild automatically detect this and
set the proper value. We do this with 'asm goto'. There's tricks in the
build system that can change the configs based on if a compiler is
broken or not.

Just to be sure.

Do you suggest to define CONFIG_DYNAMIC_FTRACE_WITH_REGS
via a check in Makefile and rename it to e.g.
CC_FTRACE_WITH_REGS.

Or should we define another variable, e.g.
CC_BROKEN_DYNAMC_FTRACE_WITH_REGS? And then replace all occurences in
the code by something like:

-#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+#if defined(CONFIG_DYNAMIC_FTRACE_WITH_REGS) && \
+    !defined(CC_BROKEN_DYNAMC_FTRACE_WITH_REGS)

?

Best Regards,
Petr