lkml.org 
[lkml]   [2013]   [Jan]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[ 29/47] ftrace: Do not function trace inlined functions
Date
3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Steven Rostedt <srostedt@redhat.com>

commit 45959ee7aa645815a5ce303a0ea1e48a21e67c6a upstream.

When gcc inlines a function, it does not mark it with the mcount
prologue, which in turn means that inlined functions are not traced
by the function tracer. But if CONFIG_OPTIMIZE_INLINING is set, then
gcc is allowed not to inline a function that is marked inline.

Depending on the options and the compiler, a function may or may
not be traced by the function tracer, depending on whether gcc
decides to inline a function or not. This has caused several
problems in the pass becaues gcc is not always consistent with
what it decides to inline between different gcc versions.

Some places should not be traced (like paravirt native_* functions)
and these are mostly marked as inline. When gcc decides not to
inline the function, and if that function should not be traced, then
the ftrace function tracer will suddenly break when it use to work
fine. This becomes even harder to debug when different versions of
gcc will not inline that function, making the same kernel and config
work for some gcc versions and not work for others.

By making all functions marked inline to not be traced will remove
the ambiguity that gcc adds when it comes to tracing functions marked
inline. All gcc versions will be consistent with what functions are
traced and having volatile working code will be removed.

Note, only the inline macro when CONFIG_OPTIMIZE_INLINING is set needs
to have notrace added, as the attribute __always_inline will force
the function to be inlined and then not traced.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/linux/compiler-gcc.h | 5 +++++
1 file changed, 5 insertions(+)

--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -50,6 +50,11 @@
# define inline inline __attribute__((always_inline))
# define __inline__ __inline__ __attribute__((always_inline))
# define __inline __inline __attribute__((always_inline))
+#else
+/* A lot of inline functions can cause havoc with function tracing */
+# define inline inline notrace
+# define __inline__ __inline__ notrace
+# define __inline __inline notrace
#endif

#define __deprecated __attribute__((deprecated))



\
 
 \ /
  Last update: 2013-01-10 00:41    [W:0.204 / U:2.340 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site