linux-kernel - Re: [PATCH v3 01/29] asm-generic: add generic futex for !CONFIG

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Date:	Tue, 23 Sep 2014 18:20:08 +0800
From:	"LF.Tan" <lftan.linux@...il.com>
To:	Linux-Arch <linux-arch@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>
Cc:	Ley Foon Tan <lftan@...era.com>,
	LeyFoon Tan <lftan.linux@...il.com>,
	Chung-Lin Tang <cltang@...esourcery.com>
Subject: Re: [PATCH v3 01/29] asm-generic: add generic futex for !CONFIG_SMP

On Mon, Sep 8, 2014 at 5:22 PM, Ley Foon Tan <lftan@...era.com> wrote:
> Follow m68k futex implementation for !CONFIG_SMP.
>
> Signed-off-by: Ley Foon Tan <lftan@...era.com>
> ---
>  include/asm-generic/futex.h | 82 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 82 insertions(+)
>
> diff --git a/include/asm-generic/futex.h b/include/asm-generic/futex.h
> index 01f227e..f5650a5 100644
> --- a/include/asm-generic/futex.h
> +++ b/include/asm-generic/futex.h
> @@ -5,6 +5,87 @@
>  #include <linux/uaccess.h>
>  #include <asm/errno.h>
>
> +#ifndef CONFIG_SMP
> +static inline int
> +futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
> +{
> +       int op = (encoded_op >> 28) & 7;
> +       int cmp = (encoded_op >> 24) & 15;
> +       int oparg = (encoded_op << 8) >> 20;
> +       int cmparg = (encoded_op << 20) >> 20;
> +       int oldval, ret;
> +       u32 tmp;
> +
> +       if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
> +               oparg = 1 << oparg;
> +
> +       pagefault_disable();    /* implies preempt_disable() */
> +
> +       ret = -EFAULT;
> +       if (unlikely(get_user(oldval, uaddr) != 0))
> +               goto out_pagefault_enable;
> +
> +       ret = 0;
> +       tmp = oldval;
> +
> +       switch (op) {
> +       case FUTEX_OP_SET:
> +               tmp = oparg;
> +               break;
> +       case FUTEX_OP_ADD:
> +               tmp += oparg;
> +               break;
> +       case FUTEX_OP_OR:
> +               tmp |= oparg;
> +               break;
> +       case FUTEX_OP_ANDN:
> +               tmp &= ~oparg;
> +               break;
> +       case FUTEX_OP_XOR:
> +               tmp ^= oparg;
> +               break;
> +       default:
> +               ret = -ENOSYS;
> +       }
> +
> +       if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
> +               ret = -EFAULT;
> +
> +out_pagefault_enable:
> +       pagefault_enable();     /* subsumes preempt_enable() */
> +
> +       if (ret == 0) {
> +               switch (cmp) {
> +               case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
> +               case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
> +               case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
> +               case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
> +               case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
> +               case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
> +               default: ret = -ENOSYS;
> +               }
> +       }
> +       return ret;
> +}
> +
> +static inline int
> +futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
> +                             u32 oldval, u32 newval)
> +{
> +       u32 val;
> +
> +       if (unlikely(get_user(val, uaddr) != 0))
> +               return -EFAULT;
> +
> +       if (val == oldval && unlikely(put_user(newval, uaddr) != 0))
> +               return -EFAULT;
> +
> +       *uval = val;
> +
> +       return 0;
> +}
> +
> +#else
>  static inline int
>  futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
>  {
> @@ -54,4 +135,5 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
>         return -ENOSYS;
>  }
>
> +#endif /* CONFIG_SMP */
>  #endif
> --
> 1.8.2.1
>

Hi Arnd

Are you okay with this generic futex in asm-generic?

Regards
Ley Foon
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