Re: [PATCH sched_ext/for-7.4] sched_ext: Work around pahole 1.32 dropping scx_bpf_task_set_lazy_resched() from BTF

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] sched: build failure due to misapplied patch in scx_bpf_task_set_dsq_vtime()
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commit 16f6b2129331609ed5db39cd3ea7260f54a1df1f
Author: Tejun Heo <tj@kernel.org>

sched_ext: Work around pahole 1.32 dropping scx_bpf_task_set_lazy_resched() from BTF

This commit works around an issue with pahole 1.32 by forcing the lazy
argument onto the stack using barrier_data() so its location doesn't
name a register.

Link: https://lore.kernel.org/r/20260925213619.2187751-1-yonghong.song@linux.dev

> diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
> index 6b037d27c99d3..feaa784d7a0dc 100644
> --- a/kernel/sched/ext/ext.c
> +++ b/kernel/sched/ext/ext.c
> @@ -10119,6 +10119,11 @@ __bpf_kfunc bool scx_bpf_task_set_dsq_vtime(struct task_struct *p, u64 vtime,
>  {
>  	struct scx_sched *sch;
>  
> +	/*
> +	 * clang's register locations for @lazy make pahole 1.32 drop this kfunc
> +	 * from BTF. Keep @lazy in memory so its location names no register.
> +	 */
> +	barrier_data(&lazy);

[Severity: Low]
Will this cause a build failure? It looks like the lazy variable is not
declared in scx_bpf_task_set_dsq_vtime().

Could it be that this patch was mistakenly applied to 
scx_bpf_task_set_dsq_vtime() instead of scx_bpf_task_set_lazy_resched()? 
They appear to share identical context lines, meaning the patch might have
matched guard(rcu)(); followed by sch = scx_prog_sched(aux); in the wrong
function.

>  	guard(rcu)();
>  	sch = scx_prog_sched(aux);
>  	if (unlikely(!sch || !scx_task_on_sched(sch, p)))
>  		return false;

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Sashiko AI review · https://sashiko.dev/#/patchset/7c139810be5ffc9764ed4236efc28794@kernel.org?part=1