Re: [PATCH] x86: fix ticket spin lock asm constraints

[Nick Piggin]

Hi,

All these ticket lock patches look pretty good to me. Thanks for going over
it so thoroughly.

On Fri, Aug 29, 2008 at 12:54:59PM +0100, Jan Beulich wrote:
> In addition to these changes I doubt the 'volatile' on all the ticket
> lock asm()-s are really necessary.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
> Cc: Nick Piggin <npiggin@xxxxxxx>
> 
> ---
>  include/asm-x86/spinlock.h |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> --- linux-2.6.27-rc5/include/asm-x86/spinlock.h	2008-08-21 14:37:34.000000000 +0200
> +++ 2.6.27-rc5-x86-spinlock-constraints/include/asm-x86/spinlock.h	2008-08-19 12:43:22.000000000 +0200
> @@ -101,7 +101,7 @@ static __always_inline int __ticket_spin
>  		     "1:"
>  		     "sete %b1\n\t"
>  		     "movzbl %b1,%0\n\t"
> -		     : "=&a" (tmp), "=Q" (new), "+m" (lock->slock)
> +		     : "=&a" (tmp), "=&Q" (new), "+m" (lock->slock)
>  		     :
>  		     : "memory", "cc");
>  
> @@ -146,7 +146,7 @@ static __always_inline void __ticket_spi
>  		     /* don't need lfence here, because loads are in-order */
>  		     "jmp 1b\n"
>  		     "2:"
> -		     : "+Q" (inc), "+m" (lock->slock), "=r" (tmp)
> +		     : "+r" (inc), "+m" (lock->slock), "=&r" (tmp)
>  		     :
>  		     : "memory", "cc");
>  }
> @@ -166,7 +166,7 @@ static __always_inline int __ticket_spin
>  		     "1:"
>  		     "sete %b1\n\t"
>  		     "movzbl %b1,%0\n\t"
> -		     : "=&a" (tmp), "=r" (new), "+m" (lock->slock)
> +		     : "=&a" (tmp), "=&q" (new), "+m" (lock->slock)
>  		     :
>  		     : "memory", "cc");
>  
> 
> 
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