Re: [PATCH v3] libtraceevent: avoid racing recursive builds of both libraries

On Mon,  1 Jun 2026 16:20:24 +0800
Cao Ruichuang <[email protected]> wrote:

> 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 has the static library depend on the shared
> library before running objcopy. Reflect that dependency at the top level
> too by also making the static library target depend on the shared library
> target. This serializes parallel top-level requests for both libraries
> while preserving the shared-before-static build order and the existing
> forced static-library recursive make.
> 
> This fixes the object-file race seen when top-level parallel builds
> request both libraries, for example via `make -j8 libs` or
> `make -j8 libtraceevent.a libtraceevent.so`.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217428
> Assisted-by: Codex:gpt-5.5
> Signed-off-by: Cao Ruichuang <[email protected]>

Thanks for the updates.

For future version updates, please start a new email thread and do not
reply to the old one. It makes it easier to manage for maintainers.

Also, the tracing code uses capital letters to start subjects:

  [PATCH v3] libtraceevent: Avoid racing recursive builds of both libraries

> ---
> Changes in v3:

In order to still keep the trail of versions, you can use lore with the
Message-ID of the previous email version:

Changes since v2: https://lore.kernel.org/all/[email protected]/

If all looks good, I'll go ahead and apply your patches.

Thanks again,

-- Steve

> - Follow Steven's review and make the top-level static library target
>   depend on the shared library target, matching src/Makefile's dependency
>   direction.
> - Preserve the existing forced static-library recursive make while
>   serializing parallel top-level requests shared-before-static.
> 
> Tested on x86_64 Linux with GNU Make 4.3, GCC 11.5.0, and GNU objcopy
> 2.35.2:
> - make -j8 libs
> - make -j8 libtraceevent.a libtraceevent.so
> - 20 iterations of: make clean && make -j8 libs
> - 10 iterations of: make clean && make -j8 libtraceevent.a libtraceevent.so
> - make -j8
> - make -j8 test
> 
>  Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index e1a10a0..d1ceaee 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -208,7 +208,7 @@ libtraceevent.so: $(bdir) $(LIBTRACEEVENT_SHARED)
>  
>  libs: libtraceevent.a libtraceevent.so
>  
> -$(LIBTRACEEVENT_STATIC): force
> +$(LIBTRACEEVENT_STATIC): force $(LIBTRACEEVENT_SHARED)
>  	$(Q)$(call descend,$(src)/src,$@)
>  
>  $(LIBTRACEEVENT_SHARED): force