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From: Tejun Heo <tj@kernel.org>
To: Andrea Righi <arighi@nvidia.com>
Cc: David Vernet <void@manifault.com>,
	Changwoo Min <changwoo@igalia.com>,
	Emil Tsalapatis <emil@etsalapatis.com>,
	David Dai <david.dai@linux.dev>,
	Yonghong Song <yonghong.song@linux.dev>,
	Alexei Starovoitov <ast@kernel.org>,
	bpf@vger.kernel.org, sched-ext@lists.linux.dev,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH sched_ext/for-7.4] sched_ext: Work around pahole 1.32 dropping scx_bpf_task_set_lazy_resched() from BTF
Date: Tue, 29 Sep 2026 09:25:02 -1000	[thread overview]
Message-ID: <arwQjsHCGl5lF7LR@slm.duckdns.org> (raw)
In-Reply-To: <arwPVufx2ZUOc_sp@gpd4>

On Tue, Sep 29, 2026 at 09:19:50PM +0200, Andrea Righi wrote:
> First of all thanks for figuring this out, it was really annoying, I've been
> holding pahole to 1.31 because of this.
> 
> I also looked a bit and it seems to be triggered specifically by the bool type.
> This is with clang 22.1.8 on x86_64 without barrier_data and only changing the
> type:
> 
>   bool  movl %esi, %ebp    -> dropped by pahole
>   u32   movl %esi, %ebp    -> ok
>   u64   movq %rsi, %r15    -> ok
> 
> With u32 the generated code is identical to the bool case, but clang keeps the
> RSI entry range, so pahole is happy.
> 
> Should we just change lazy to u32 (or use a u64 flags) instead of using
> barrier_data()?

I mean, bool is the right and I'm hoping clang can be fixed and the
workaround seems to work, so keep it as-is unless there are other reasons to
change it (e.g. this becomes a wider interface taking u64 flags or sth like
that)?

Thanks.

-- 
tejun

  reply	other threads:[~2026-09-29 19:25 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-29 17:32 Tejun Heo
2026-09-29 19:19 ` Andrea Righi
2026-09-29 19:25   ` Tejun Heo [this message]
2026-09-29 19:37     ` Andrea Righi
2026-09-29 23:11 ` Tejun Heo
2026-09-30  0:59 ` bot+bpf-ci

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