Re: [PATCH sched_ext/for-7.4] tools/sched_ext: Skip scx_lib_init_probe() without CONFIG_FUNCTION_TRACER

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The SCX_OPS_LOAD macro introduces a hard compile-time dependency on `scx_lib_init_probe` existing in the user's BPF skeleton, which will cause a C compiler error for schedulers that do not define this probe.
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--- Patch [1]: [PATCH sched_ext/for-7.4] tools/sched_ext: Skip scx_lib_init_probe() without CONFIG_FUNCTION_TRACER ---
commit fc2df7f154a3b0d6909630ef49d7036552669ee3
Author: Cheng-Yang Chou <yphbchou0911@gmail.com>

tools/sched_ext: Skip scx_lib_init_probe() without CONFIG_FUNCTION_TRACER

This commit updates the SCX_OPS_LOAD macro to conditionally disable
autoload for the scx_lib_init_probe program if function tracing is
unavailable. It also modifies the post-load loop to skip programs that
have autoload disabled.

> diff --git a/tools/sched_ext/include/scx/compat.h b/tools/sched_ext/include/scx/compat.h
> --- a/tools/sched_ext/include/scx/compat.h
> +++ b/tools/sched_ext/include/scx/compat.h

[ ... ]

>  /* See SCX_OPS_OPEN() above for backward-compatibility handling. */
>  #define SCX_OPS_LOAD(__skel, __ops_name, __scx_name, __uei_name) ({		\
>  	struct bpf_program *__prog;						\
>  	UEI_SET_SIZE(__skel, __ops_name, __uei_name);				\
> +	if (!__COMPAT_function_tracer_available())				\
> +		bpf_program__set_autoload((__skel)->progs.scx_lib_init_probe, false); \

[Severity: Medium]
Will this cause a compile-time failure for out-of-tree schedulers that do
not include a scx_lib_init_probe program?

Skeletons generated by bpftool only contain fields for BPF programs that
are actually present in the BPF object. If a user's scheduler skeleton
lacks this specific probe, (__skel)->progs.scx_lib_init_probe won't exist
in the generated struct and will trigger a C compiler error when invoking
this macro.

Could this look up the program dynamically using
bpf_object__find_program_by_name() at runtime instead, to avoid breaking
compilation for schedulers without this probe?

>  	SCX_BUG_ON(__scx_name##__load((__skel)), "Failed to load skel");	\

[ ... ]

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Sashiko AI review · https://sashiko.dev/#/patchset/20260824155051.20841-1-yphbchou0911@gmail.com?part=1