Re: [PATCH v3 10/17] perf build: Pre-generate BPF skeleton tooling during umbrella prepare phase

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The `bpf-skel-prepare` target relies on an undefined variable `$(bpf_skel_deps)`, causing the pre-generation to be silently skipped and introducing a parallel build race condition.
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commit aa0df16c70b52c768c1153976cf365e149c64c2f
Author: Ian Rogers <irogers@google.com>

perf build: Pre-generate BPF skeleton tooling during umbrella prepare phase

This commit decouples BPF skeleton tooling generation by attaching a new
bpf-skel-prepare target to the umbrella prepare target. This is intended
to compile bpftool and dump vmlinux.h early to eliminate sub-make startup
bottlenecks.

> diff --git a/tools/perf/bpf_skel.mak b/tools/perf/bpf_skel.mak
> index 30924ad140c49..1fbd8dfefa5eb 100644
> --- a/tools/perf/bpf_skel.mak
> +++ b/tools/perf/bpf_skel.mak
> @@ -15,6 +15,10 @@ ifeq ($(CONFIG_PERF_BPF_SKEL),y)
>  BPFTOOL := $(SKEL_TOOL_TMP_OUT)/bootstrap/bpftool
>  VMLINUX_H := $(SKEL_TOOL_OUT)/vmlinux.h
>  
> +.PHONY: bpf-skel-prepare
> +bpf-skel-prepare: $(bpf_skel_deps)

Is $(bpf_skel_deps) defined anywhere?

It looks like this variable is never defined, meaning bpf-skel-prepare
evaluates with no prerequisites and executes as a no-op during the prepare
phase.

If bpftool and vmlinux.h are not pre-generated here, will concurrent
sub-makes that independently include bpf_skel.mak simultaneously attempt
to evaluate and build the missing $(BPFTOOL) dependency?

This could cause multiple independent Make instances to concurrently enter
../bpf/bpftool and write to the same output directories, leading to parallel
build corruption and failures.

> +	@:

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Sashiko AI review · https://sashiko.dev/#/patchset/20260514163409.927816-1-irogers@google.com?part=10