| From: Steven Rostedt <srostedt@redhat.com> |
| Date: Mon, 12 Dec 2011 15:22:41 -0500 |
| Subject: ftrace: Do not function trace inlined functions |
| |
| 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: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| include/linux/compiler-gcc.h | 5 +++++ |
| 1 file changed, 5 insertions(+) |
| |
| diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h |
| index 59e4028..3fd17c2 100644 |
| --- 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)) |
