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

Nick Piggin
2008-08-30T05:28:18Z

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@novell.com>
> Cc: Nick Piggin <npiggin@suse.de>
>
> ---
> 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");
>
>
>