Re: [PATCH 03/20] x86/ticketlock: Use C for __ticket_spin_unlock

[Paolo Bonzini]

On 11/13/2010 11:05 AM, Américo Wang wrote:
> On Wed, Nov 03, 2010 at 10:59:44AM -0400, Jeremy Fitzhardinge wrote:
> >   * On PPro SMP or if we are using OOSTORE, we use a locked operation to unlock
> >   * (PPro errata 66, 92)
> >   */
> > -# define UNLOCK_LOCK_PREFIX LOCK_PREFIX
> > +static __always_inline void __ticket_unlock_release(struct arch_spinlock *lock)
> > +{
> > +	if (sizeof(lock->tickets.head) == sizeof(u8))
> > +		asm (LOCK_PREFIX "incb %0"
> > +		     : "+m" (lock->tickets.head) : : "memory");
> > +	else
> > +		asm (LOCK_PREFIX "incw %0"
> > +		     : "+m" (lock->tickets.head) : : "memory");
>
> This 'if/else' really should be done with #ifdef, even though
> the compiler may be smart enough to remove it.

That's a sure path to bitrot.

Paolo
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