Received-SPF: pass (google.com: domain of linux-kernel+bounces-153935-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Feedback-ID: iad51458e:Fastmail
Date: Mon, 22 Apr 2024 12:45:25 -0700
From: Boqun Feng <boqun.feng@gmail.com>
To: Uros Bizjak <ubizjak@gmail.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>, Will Deacon <will@kernel.org>,
	Waiman Long <longman@redhat.com>
Subject: Re: [PATCH] locking/pvqspinlock/x86: Use _Q_LOCKED_VAL in
 PV_UNLOCK_ASM macro
Message-ID: <Zia-VeObR-m6Bf39@boqun-archlinux>
References: <20240422151752.53997-1-ubizjak@gmail.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240422151752.53997-1-ubizjak@gmail.com>

On Mon, Apr 22, 2024 at 05:17:35PM +0200, Uros Bizjak wrote:
> Use _Q_LOCKED_VAL instead of hardcoded $0x1 in PV_UNLOCK_ASM macro.
> 
> No functional changes intended.
> 
> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Will Deacon <will@kernel.org>
> Cc: Waiman Long <longman@redhat.com>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> ---
>  arch/x86/include/asm/qspinlock_paravirt.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/qspinlock_paravirt.h b/arch/x86/include/asm/qspinlock_paravirt.h
> index 466af57b8ed6..0a985784be9b 100644
> --- a/arch/x86/include/asm/qspinlock_paravirt.h
> +++ b/arch/x86/include/asm/qspinlock_paravirt.h
> @@ -40,7 +40,7 @@ __PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock_slowpath, ".spinlock.text");
>  #define PV_UNLOCK_ASM							\
>  	FRAME_BEGIN							\
>  	"push  %rdx\n\t"						\
> -	"mov   $0x1,%eax\n\t"						\
> +	"mov   $" __stringify(_Q_LOCKED_VAL) ",%eax\n\t"		\
>  	"xor   %edx,%edx\n\t"						\
>  	LOCK_PREFIX "cmpxchg %dl,(%rdi)\n\t"				\
>  	"jne   .slowpath\n\t"						\

There is also a "cmp $0x1,%al" afterwards.

Regards,
Boqun

> -- 
> 2.42.0
>