linux-kernel - Re: [PATCH] generic arch_futex_atomic_op

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Date:   Mon, 15 Jul 2019 15:13:32 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Vasily Averin <vvs@...tuozzo.com>
cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] generic arch_futex_atomic_op_inuser() cleanup

On Mon, 15 Jul 2019, Vasily Averin wrote:

> Access to 'op' variable does not require pagefault_disable(),
> 'ret' variable should be initialized before using,
> 'oldval' variable can be replaced by constant.
> 
> Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
> ---
>  include/asm-generic/futex.h | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/include/asm-generic/futex.h b/include/asm-generic/futex.h
> index 8666fe7f35d7..e9a9655d786d 100644
> --- a/include/asm-generic/futex.h
> +++ b/include/asm-generic/futex.h
> @@ -118,9 +118,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
>  static inline int
>  arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
>  {
> -	int oldval = 0, ret;
> -
> -	pagefault_disable();
> +	int ret = 0;

The variable is clearly initialized before using in 'default:', but the
whole function is pretty useless. It's guaranteed to return -ENOSYS and
does nothing else than disabling/enabling pagefaults for no reason.

Thanks,

	tglx