Re: [PATCH v2 2/2] kbuild: trace functions in subdirectories of lib/

[Steven Rostedt]

On Tue,  7 Jul 2020 18:21:17 +0900
Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote:

>   ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> 
> exists here in sub-directories of lib/ to keep the behavior of
> commit 2464a609ded0 ("ftrace: do not trace library functions").
> 
> Since that commit, not only the objects in lib/ but also the ones in
> the sub-directories are excluded from ftrace (although the commit
> description did not explicitly mention this).
> 
> However, most of library functions in sub-directories are not so hot.
> Re-add them to ftrace.

I'm OK with this change, but note, it wasn't just the hot path that I
disabled ftrace on lib for, but some of these calls are done very early
at boot up. It may have been PowerPC that I was stumbling over. The
issue is that they would call mcount before the kernel was mapped
properly, and the system would crash.

My PowerPC box no longer boots so I can't test this anymore. But a lot
has changed since 2008, and all this may very well be OK.

-- Steve