linux-kernel - Re: [RFC PATCH] tools/sched_ext: Use u64 for kind field to fix ARM64 atomic ops

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Message-ID: <CAB8ipk8H65Kn+Cg8cVuLCwgcvWP_Q4tXUS1hqr_cSweV=DZFtQ@mail.gmail.com>
Date: Tue, 10 Feb 2026 09:48:23 +0800
From: Xuewen Yan <xuewen.yan94@...il.com>
To: Tejun Heo <tj@...nel.org>
Cc: Xuewen Yan <xuewen.yan@...soc.com>, void@...ifault.com, arighi@...dia.com, 
	changwoo@...lia.com, guohua.yan@...soc.com, ke.wang@...soc.com, 
	di.shen@...soc.com, sched-ext@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	bpf@...r.kernel.org
Subject: Re: [RFC PATCH] tools/sched_ext: Use u64 for kind field to fix ARM64
 atomic ops

On Tue, Feb 10, 2026 at 3:11 AM Tejun Heo <tj@...nel.org> wrote:
>
> On Mon, Feb 09, 2026 at 04:55:36PM +0800, Xuewen Yan wrote:
> > From: Guohua Yan <guohua.yan@...soc.com>
> >
> > There are following compile errors in arm64:
> >
> > bpftools/CORE/scx_simple.bpf.c:144:2: error: unsupported atomic operation, please use 64 bit version
> >   144 |         UEI_RECORD(uei, ei);
> >       |         ^
> >
> > Convert kind from int to u64 to resolve ARM64 atomic operation
> > limitations. ARM64 primarily supports 64-bit atomic operations.
>
> Alexei says this is llvm bpf backend error and the answer is to upgrade to a
> modern llvm that defaults to -mcpu=v3.

Thank you for the insight. We'll upgrade our LLVM toolchain and test
with -mcpu=v3.
Appreciate your guidance on this backend issue.

Thanks！