From 45959ee7aa645815a5ce303a0ea1e48a21e67c6a Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Mon, 12 Dec 2011 15:22:41 -0500 Subject: ftrace: Do not function trace inlined functions 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 --- 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 59e4028e833d..3fd17c249221 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)) -- cgit v1.2.3