Re: [PATCH] futex: cmpxchg_futex_value_locked API change

[Martin Schwidefsky <schwidefsky@de.ibm.com>]

On Sun, 6 Mar 2011 18:11:27 -0800
Michel Lespinasse <walken@google.com> wrote:

> Aplogies for the long CC list - as this proposal involves asm changes
> in many architectures, and I have only been able to test on x86,
> I have tried to include one maintainer from every arch so they can
> hopefully double check me. I do think I got all architectures right,
> but you can never be 100% sure...
> 
> -static int __futex_atomic_cmpxchg_pt(int __user *uaddr, int oldval, int newval)
> +static int __futex_atomic_cmpxchg_pt(int *uval, int __user *uaddr,
> +				     int oldval, int newval)
>  {
>  	int ret;
> 
>  	asm volatile("0: cs   %1,%4,0(%5)\n"
> -		     "1: lr   %0,%1\n"
> +		     "1: l    %0,0\n"
>  		     "2:\n"
>  		     EX_TABLE(0b,2b) EX_TABLE(1b,2b)
>  		     : "=d" (ret), "+d" (oldval), "=m" (*uaddr)
>  		     : "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
>  		     : "cc", "memory" );
> +	*uval = oldval;
>  	return ret;
>  }

That "l %0,0" is incorrect; if you want to load a zero into %0 you can use "la %0,0".

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.