[Buildroot] [PATCH v2] package/linux-tools/linux-tool-perf.mk.in: fix doc build issue

[Buildroot] [PATCH v2] package/linux-tools/linux-tool-perf.mk.in: fix doc build issue

[Markus Mayer via buildroot]

Address potential document build issue when BR2_PER_PACKAGE_DIRECTORIES
is enabled.

The perf package wants to prevent the documentation from being built,
since it won't be installed anyway. The trick is to create an empty
GNUmakefile in the proper place. It did this by using a POST_PATCH hook.

The reason this approach works when BR2_PER_PACKAGE_DIRECTORIES is off
is that the build system ensures only one package builds at a time, so
Linux's "extract" stage and Linux Tool's "patch" stage can never execute
in parallel.

However, with per-package builds enabled, there is no guarantee that
Linux has finished extracting by the time the linux-tool's POST_PATCH
hook runs. This means the creation of GNUmakefile could silently be
skipped if that portion of the source code hadn't been extracted yet.
If, in addition to this, asciidoc happened to be installed on the build
host (/usr/bin/asciidoc), perf would detect this and enable the doc
build stage. At actual build time, it would use host-python3 (not the
host's system Python), which does NOT have asciidoc, and the build would
fail.

  INSTALL libperf_headers
  SYSHDR  /local/users/jenkins/workspace/[...]/libperf/arch/[...]/unistd_64.h
  INSTALL libbpf_headers
fatal: not a git repository: '.'
  ASCIIDOC /local/users/jenkins/workspace/[...]/tools/perf/perf-amd-ibs.xml
fatal: not a git repository: '.'
[...]
  ASCIIDOC /local/users/jenkins/workspace/[...]/tools/perf/perf-data.xml
/local/users/jenkins/workspace/buildroot/[...]/host/bin/python3:
No module named asciidoc
make[5]: *** [Makefile:275: [...]/perf-data.xml] Error 1

Turning the POST_PATCH hook into a PRE_CONFIGURE hook solves this timing
problem and guarantees that the "fake" GNUmakefile can be injected into
$(LINUX_DIR)/tools/perf/Documentation as intended.

Signed-off-by: Markus Mayer <markus.mayer@broadcom.com>
---
 package/linux-tools/linux-tool-perf.mk.in | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

The primary reason for v2 is the updated email address. While I was at it, I
made the comment a little clearer. The actual code change is identical to
before.

https://lists.buildroot.org/pipermail/buildroot/2026-September/810498.html

diff --git a/package/linux-tools/linux-tool-perf.mk.in b/package/linux-tools/linux-tool-perf.mk.in
index 8c91c2cc6b0f..3271fd5683eb 100644
--- a/package/linux-tools/linux-tool-perf.mk.in
+++ b/package/linux-tools/linux-tool-perf.mk.in
@@ -141,12 +141,17 @@ endif
 # distributions.
 # We name it 'GNUmakefile' so that GNU make will use it instead of
 # the existing 'Makefile'.
+#
+# This must be a PRE_CONFIGURE hook, not a POST_PATCH hook. Only the
+# configure step is ordered after "linux" (via LINUX_TOOLS_DEPENDENCIES).
+# For a POST_PATCH hook, tools/perf/Documentation/Makefile is not
+# guaranteed to exist yet.
 define PERF_DISABLE_DOCUMENTATION
 	if [ -f $(LINUX_DIR)/tools/perf/Documentation/Makefile ]; then \
 		printf "%%:\n\t@:\n" >$(LINUX_DIR)/tools/perf/Documentation/GNUmakefile; \
 	fi
 endef
-LINUX_TOOLS_POST_PATCH_HOOKS += PERF_DISABLE_DOCUMENTATION
+LINUX_TOOLS_PRE_CONFIGURE_HOOKS += PERF_DISABLE_DOCUMENTATION
 
 # O must be redefined here to overwrite the one used by Buildroot for
 # out of tree build. We build perf in $(LINUX_DIR)/tools/perf/ and not just
-- 
2.55.0

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Re: [Buildroot] [PATCH v2] package/linux-tools/linux-tool-perf.mk.in: fix doc build issue

[Florian Fainelli via buildroot]

On 10/15/26 15:29, Markus Mayer via buildroot wrote:
> Address potential document build issue when BR2_PER_PACKAGE_DIRECTORIES
> is enabled.
> 
> The perf package wants to prevent the documentation from being built,
> since it won't be installed anyway. The trick is to create an empty
> GNUmakefile in the proper place. It did this by using a POST_PATCH hook.
> 
> The reason this approach works when BR2_PER_PACKAGE_DIRECTORIES is off
> is that the build system ensures only one package builds at a time, so
> Linux's "extract" stage and Linux Tool's "patch" stage can never execute
> in parallel.
> 
> However, with per-package builds enabled, there is no guarantee that
> Linux has finished extracting by the time the linux-tool's POST_PATCH
> hook runs. This means the creation of GNUmakefile could silently be
> skipped if that portion of the source code hadn't been extracted yet.
> If, in addition to this, asciidoc happened to be installed on the build
> host (/usr/bin/asciidoc), perf would detect this and enable the doc
> build stage. At actual build time, it would use host-python3 (not the
> host's system Python), which does NOT have asciidoc, and the build would
> fail.
> 
>    INSTALL libperf_headers
>    SYSHDR  /local/users/jenkins/workspace/[...]/libperf/arch/[...]/unistd_64.h
>    INSTALL libbpf_headers
> fatal: not a git repository: '.'
>    ASCIIDOC /local/users/jenkins/workspace/[...]/tools/perf/perf-amd-ibs.xml
> fatal: not a git repository: '.'
> [...]
>    ASCIIDOC /local/users/jenkins/workspace/[...]/tools/perf/perf-data.xml
> /local/users/jenkins/workspace/buildroot/[...]/host/bin/python3:
> No module named asciidoc
> make[5]: *** [Makefile:275: [...]/perf-data.xml] Error 1
> 
> Turning the POST_PATCH hook into a PRE_CONFIGURE hook solves this timing
> problem and guarantees that the "fake" GNUmakefile can be injected into
> $(LINUX_DIR)/tools/perf/Documentation as intended.
> 
> Signed-off-by: Markus Mayer <markus.mayer@broadcom.com>

Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
-- 
Florian

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