linux-kernel - Re: [PATCH v8 5/5] arm64: futex: support futex with FEAT

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Message-ID: <aMq6q1OGc3InfoNA@e129823.arm.com>
Date: Wed, 17 Sep 2025 14:42:03 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: Mark Rutland <mark.rutland@....com>
Cc: catalin.marinas@....com, will@...nel.org, broonie@...nel.org,
	maz@...nel.org, oliver.upton@...ux.dev, joey.gouly@....com,
	james.morse@....com, ardb@...nel.org, scott@...amperecomputing.com,
	suzuki.poulose@....com, yuzenghui@...wei.com,
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 5/5] arm64: futex: support futex with FEAT_LSUI

[...]
> static __always_inline int
> __lsui_cmpxchg32(u32 __user *uaddr, u32 oldval, u32 newval, u32 *oval)
> {
> 	uaddr64 = (u64 __user *)PTR_ALIGN_DOWN(uaddr, sizeof(u64));
> 	u64 oval64, nval64, orig64;
>
> 	if (get_user(oval64, uaddr64)
> 		return -EFAULT;
>
> 	if (IS_ALIGNED(addr, sizeof(u64)) == IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN))  {
> 		FIELD_MODIFY(GENMASK_U64(31, 0), &oval64, oldval);
> 		FIELD_MODIFY(GENMASK_U64(31, 0), &nval64, newval);
> 	} else {
> 		FIELD_MODIFY(GENMASK_U64(63, 32), &oval64, oldval);
> 		FIELD_MODIFY(GENMASK_U64(63, 32), &nval64, newval);
> 	}
> 	orig64 = oval64;
>
> 	if (__lsui_cmpxchg64(uaddr_al, &oval64, nval64))
> 		return -EFAULT;
>
> 	if (oval64 != orig64)
> 		return -EAGAIN;
>
> 	*oval = oldval;
> 	return 0;
> }

Oh, I misread the condition. Thanks for your suggetion.
Please ignore my previous email.

--
Sincerely,
Yeoreum Yun