From: Will Deacon <will.deacon@arm.com>
To: "Yandong.Zhao" <yandong77520@gmail.com>
Cc: Dave.Martin@arm.com, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, ard.biesheuvel@linaro.org,
catalin.marinas@arm.com, zhaoyd@thundersoft.com,
zhaoxb@thundersoft.com, fanlc0801@thundersoft.com
Subject: Re: [PATCH] arm64: neon: Fix function may_use_simd() return error status
Date: Wed, 11 Jul 2018 13:05:19 +0100 [thread overview]
Message-ID: <20180711120519.GC15725@arm.com> (raw)
In-Reply-To: <1531307188-12032-1-git-send-email-yandong77520@gmail.com>
On Wed, Jul 11, 2018 at 07:06:28PM +0800, Yandong.Zhao wrote:
> From: Yandong Zhao <yandong77520@gmail.com>
>
> It does not matter if the caller of may_use_simd() migrates to
> another cpu after the call, but it is still important that the
> kernel_neon_busy percpu instance that is read matches the cpu the
> task is running on at the time of the read.
>
> This means that raw_cpu_read() is not sufficient. kernel_neon_busy
> may appear true if the caller migrates during the execution of
> raw_cpu_read() and the next task to be scheduled in on the initial
> cpu calls kernel_neon_begin().
>
> This patch replaces raw_cpu_read() with this_cpu_read() to protect
> against this race.
>
> Fixes: cb84d11e1625 ("arm64: neon: Remove support for nested or hardirq kernel-mode NEON")
> Reviewed-by: Dave Martin <Dave.Martin@arm.com>
> Signed-off-by: Yandong Zhao <yandong77520@gmail.com>
> ---
> arch/arm64/include/asm/simd.h | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
Does this need to go to stable?
Will
next prev parent reply other threads:[~2018-07-11 12:04 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-11 11:06 [PATCH] arm64: neon: Fix function may_use_simd() return error status Yandong.Zhao
2018-07-11 12:05 ` Will Deacon [this message]
2018-07-11 12:58 ` Dave Martin
-- strict thread matches above, loose matches on Subject: below --
2018-07-12 3:29 Yandong.Zhao
2018-07-12 9:56 ` Dave Martin
2018-07-11 1:09 Yandong.Zhao
2018-07-11 7:20 ` Ard Biesheuvel
2018-07-11 15:47 ` Mark Rutland
2018-07-11 16:03 ` Will Deacon
2018-07-11 16:07 ` Mark Rutland
2018-07-11 10:55 ` Dave Martin
2018-07-10 2:21 Yandong.Zhao
2018-07-10 13:11 ` Dave Martin
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