Subject: Re: -mprofile-kernel vs. notrace in ppc64(le) Linux kernels

From: Anton Blanchard <[email-masked]>
Date: Sun, 27 Sep 2015 09:03:48 +1000

Hi,

> On Sat, Sep 26, 2015 at 04:30:08PM +0200, Torsten Duwe wrote:
> > As I mentioned earlier this year, it's a bad idea to call _mcount
> > from MMU helper functions (e.g. hash_page...), when the
> > profiling/tracing/ live-patching/whatever framewok might in turn
> > cause another such fault. Jikos suggested to use fine-grained
> > control of these functions with the "notrace" keyword in the Linux
> > kernel. It is mapped to GCC's (4.8, FWIW)
> > __attribute__((no_instrument_function)), which, to my surprise,
> > works for -p and -pg nicely, but does not affect -mprofile-kernel
> > at all!
> 
> That is surprising; please file a GCC bug.

This sounds like the issue below, fixed by Pat.

Anton
--

commit ccebc2aad32917f3371ae6d5774f689c86ace0b2
Author: pthaugen <pthaugen@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Wed Jan 15 23:48:12 2014 +0000

    	* config/rs6000/rs6000.c (rs6000_output_function_prologue): Check if
    	current procedure should be profiled.

    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@206650 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2781bd0..0788036 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2014-01-15  Pat Haugen  <[email-masked]>
+
+	* config/rs6000/rs6000.c (rs6000_output_function_prologue): Check if
+	current procedure should be profiled.
+
 2014-01-15  Andrew Pinski  <[email-masked]>
 
 	* config/aarch64/aarch64.c (aarch64_register_move_cost): Correct cost
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 289b52c..a479219 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -23198,7 +23198,7 @@ rs6000_output_function_prologue (FILE *file,
   /* Output -mprofile-kernel code.  This needs to be done here instead of
      in output_function_profile since it must go after the ELFv2 ABI
      local entry point.  */
-  if (TARGET_PROFILE_KERNEL)
+  if (TARGET_PROFILE_KERNEL && crtl->profile)
     {
       gcc_assert (DEFAULT_ABI == ABI_AIX || DEFAULT_ABI == ABI_ELFv2);
       gcc_assert (!TARGET_32BIT);