Re: [PATCH] arm64: neon: Fix function may_use_simd() return error status

[Will Deacon]

On Wed, Jul 11, 2018 at 07:06:28PM +0800, Yandong.Zhao wrote:
> From: Yandong Zhao <yandong77520@xxxxxxxxx>
> 
> 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@xxxxxxx>
> Signed-off-by: Yandong Zhao <yandong77520@xxxxxxxxx>
> ---
>  arch/arm64/include/asm/simd.h | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

Does this need to go to stable?

Will