Re: [PATCH v2] libtraceevent: avoid racing recursive builds of both libraries

On Mon,  6 Apr 2026 14:28:55 +0800
CaoRuichuang <[email protected]> wrote:

Sorry for the late reply, I've been quite busy on the kernel side of things.

> A top-level parallel build currently starts separate recursive makes for
> libtraceevent.a and libtraceevent.so. Both sub-makes rebuild the same
> object files in the same output directory, which can corrupt the .o
> files and make the final link fail with file format errors.
> 
> The src/ Makefile already builds libtraceevent.so as part of the
> libtraceevent.a target. Reflect that at the top level too by making the
> shared library target depend on the static library target, so parallel
> requests for either or both libraries funnel through a single recursive
> make.
> 
> This fixes repeated `make -j8`, `make -j8 libs`, and
> `make -j8 libtraceevent.a libtraceevent.so` failures in a Linux VM,
> where the unfixed tree reproduces the race within a few runs.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217428
> Signed-off-by: CaoRuichuang <[email protected]>
> ---
>  Makefile | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index e1a10a0..6649303 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -211,8 +211,7 @@ libs: libtraceevent.a libtraceevent.so
>  $(LIBTRACEEVENT_STATIC): force
>  	$(Q)$(call descend,$(src)/src,$@)
>  
> -$(LIBTRACEEVENT_SHARED): force
> -	$(Q)$(call descend,$(src)/src,libtraceevent.so)
> +$(LIBTRACEEVENT_SHARED): $(LIBTRACEEVENT_STATIC)

As you state in the change log, "Makefile already builds
libtraceevent.so as part of the libtraceevent.a target", wouldn't that
mean the above should be:

$(LIBTRACEEVENT_STATIC): $(LIBTRACEEVENT_SHARED)

$(LIBTRACEEVENT_SHARED): force
	$(Q)$(call descend,$(src)/src,libtraceevent.so)

??

BTW, thanks for working on this. Sorry I couldn't get to it earlier.

-- Steve


>  
>  $(bdir)/libtraceevent.so: $(bdir)/libtraceevent.so.$(EP_VERSION)
>  	@ln -sf $(<F) $@