linux-kernel - Re: [PATCH 2/2] ARM: mcs_spinlock: Drop smp_wmb in arch_mcs_spin_lock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20210127222241.GC848@willie-the-truck>
Date:   Wed, 27 Jan 2021 22:22:42 +0000
From:   Will Deacon <will@...nel.org>
To:     Alexander A Sverdlin <alexander.sverdlin@...ia.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] ARM: mcs_spinlock: Drop smp_wmb in
 arch_mcs_spin_lock_contended()

On Wed, Jan 27, 2021 at 09:01:09PM +0100, Alexander A Sverdlin wrote:
> From: Alexander Sverdlin <alexander.sverdlin@...ia.com>
> 
> Drop smp_wmb in arch_mcs_spin_lock_contended() after adding in into
> ARCH-independent code.
> 
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...ia.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