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From: Will Deacon <will@kernel.org>
To: Alexander A Sverdlin <alexander.sverdlin@nokia.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org,
	Russell King <linux@armlinux.org.uk>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/2] ARM: mcs_spinlock: Drop smp_wmb in arch_mcs_spin_lock_contended()
Date: Wed, 27 Jan 2021 22:22:42 +0000	[thread overview]
Message-ID: <20210127222241.GC848@willie-the-truck> (raw)
In-Reply-To: <20210127200109.16412-2-alexander.sverdlin@nokia.com>

On Wed, Jan 27, 2021 at 09:01:09PM +0100, Alexander A Sverdlin wrote:
> From: Alexander Sverdlin <alexander.sverdlin@nokia.com>
> 
> Drop smp_wmb in arch_mcs_spin_lock_contended() after adding in into
> ARCH-independent code.
> 
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
> ---
>  arch/arm/include/asm/mcs_spinlock.h | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/arch/arm/include/asm/mcs_spinlock.h b/arch/arm/include/asm/mcs_spinlock.h
> index 529d2cf..d8fa921 100644
> --- a/arch/arm/include/asm/mcs_spinlock.h
> +++ b/arch/arm/include/asm/mcs_spinlock.h
> @@ -8,8 +8,6 @@
>  /* MCS spin-locking. */
>  #define arch_mcs_spin_lock_contended(lock)				\
>  do {									\
> -	/* Ensure prior stores are observed before we enter wfe. */	\
> -	smp_mb();							\

I think this is the right place for the barrier, not in the core code.

Will

WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org>
To: Alexander A Sverdlin <alexander.sverdlin@nokia.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Russell King <linux@armlinux.org.uk>
Subject: Re: [PATCH 2/2] ARM: mcs_spinlock: Drop smp_wmb in arch_mcs_spin_lock_contended()
Date: Wed, 27 Jan 2021 22:22:42 +0000	[thread overview]
Message-ID: <20210127222241.GC848@willie-the-truck> (raw)
In-Reply-To: <20210127200109.16412-2-alexander.sverdlin@nokia.com>

On Wed, Jan 27, 2021 at 09:01:09PM +0100, Alexander A Sverdlin wrote:
> From: Alexander Sverdlin <alexander.sverdlin@nokia.com>
> 
> Drop smp_wmb in arch_mcs_spin_lock_contended() after adding in into
> ARCH-independent code.
> 
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
> ---
>  arch/arm/include/asm/mcs_spinlock.h | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/arch/arm/include/asm/mcs_spinlock.h b/arch/arm/include/asm/mcs_spinlock.h
> index 529d2cf..d8fa921 100644
> --- a/arch/arm/include/asm/mcs_spinlock.h
> +++ b/arch/arm/include/asm/mcs_spinlock.h
> @@ -8,8 +8,6 @@
>  /* MCS spin-locking. */
>  #define arch_mcs_spin_lock_contended(lock)				\
>  do {									\
> -	/* Ensure prior stores are observed before we enter wfe. */	\
> -	smp_mb();							\

I think this is the right place for the barrier, not in the core code.

Will

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  reply	other threads:[~2021-01-27 23:06 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-27 20:01 [PATCH 1/2] qspinlock: Ensure writes are pushed out of core write buffer Alexander A Sverdlin
2021-01-27 20:01 ` Alexander A Sverdlin
2021-01-27 20:01 ` [PATCH 2/2] ARM: mcs_spinlock: Drop smp_wmb in arch_mcs_spin_lock_contended() Alexander A Sverdlin
2021-01-27 20:01   ` Alexander A Sverdlin
2021-01-27 22:22   ` Will Deacon [this message]
2021-01-27 22:22     ` Will Deacon
2021-01-27 22:21 ` [PATCH 1/2] qspinlock: Ensure writes are pushed out of core write buffer Will Deacon
2021-01-27 22:21   ` Will Deacon
2021-01-28  7:36   ` Alexander Sverdlin
2021-01-28  7:36     ` Alexander Sverdlin
2021-01-28 11:24     ` Peter Zijlstra
2021-01-28 11:24       ` Peter Zijlstra
2021-01-27 22:43 ` Peter Zijlstra
2021-01-27 22:43   ` Peter Zijlstra
2021-01-28  7:42   ` Alexander Sverdlin
2021-01-28  7:42     ` Alexander Sverdlin

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