From: Alexander Gordeev <agordeev@linux.ibm.com>
To: Heiko Carstens <hca@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org
Subject: Re: [PATCH 2/4] s390/percpu: Drop unused output register from arch_this_cpu_add()
Date: Mon, 12 Oct 2026 16:34:44 +0200 [thread overview]
Message-ID: <23b62609-3744-4b6b-8a80-3ae1b0edd07c-agordeev@linux.ibm.com> (raw)
In-Reply-To: <20261012114249.2898572-3-hca@linux.ibm.com>
On Mon, Oct 12, 2026 at 01:42:47PM +0200, Heiko Carstens wrote:
> The laa/laag instructions return the old memory content, but
> arch_this_cpu_add() does not need it. Instead of allocating a dedicated
> output register old__ just to discard the returned value, change the
> val__ constraint from "d" to "+&d" so it is used as input/output
> register.
>
> This reduces register pressure.
>
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
> arch/s390/include/asm/percpu.h | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
next prev parent reply other threads:[~2026-10-12 14:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-12 11:42 [PATCH 0/4] s390/percpu: More small improvements Heiko Carstens
2026-10-12 11:42 ` [PATCH 1/4] s390/percpu: Use asm_inline for arch_this_cpu_add() Heiko Carstens
2026-10-12 12:41 ` Alexander Gordeev
2026-10-12 11:42 ` [PATCH 2/4] s390/percpu: Drop unused output register from arch_this_cpu_add() Heiko Carstens
2026-10-12 13:24 ` Alexander Gordeev
2026-10-12 14:16 ` Heiko Carstens
2026-10-12 14:34 ` Alexander Gordeev [this message]
2026-10-12 11:42 ` [PATCH 3/4] s390/percpu: Drop unused output register from arch_this_cpu_to_op() Heiko Carstens
2026-10-12 14:35 ` Alexander Gordeev
2026-10-12 11:42 ` [PATCH 4/4] s390/percpu: Implement this_cpu_try_cmpxchg() Heiko Carstens
2026-10-12 15:11 ` Alexander Gordeev
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