On Mon, Jun 10, 2013 at 05:08:25PM -0400, Steven Rostedt wrote:
> On Sun, 2013-06-09 at 12:36 -0700, Paul E. McKenney wrote:
> >
> > +#else /* #ifndef CONFIG_TICKET_LOCK_QUEUED */
> > +
> > +bool tkt_spin_pass(arch_spinlock_t *ap, struct __raw_tickets inc);
> > +
> > +static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
> > +{
> > + register struct __raw_tickets inc = { .tail = 2 };
> > +
> > + inc = xadd(&lock->tickets, inc);
> > + for (;;) {
> > + if (inc.head == inc.tail || tkt_spin_pass(lock, inc))
> > + break;
> > + inc.head = ACCESS_ONCE(lock->tickets.head);
> > + }
> > + barrier(); /* smp_mb() on Power or ARM. */
> > +}
> > +
> > +#endif /* #else #ifndef CONFIG_TICKET_LOCK_QUEUED */
> > +
>
> To avoid the above code duplication, I would have this instead:
Nice! I have updated accordingly.
Thanx, Paul
> #ifdef CONFIG_TICKET_LOCK_QUEUED
>
> bool tkt_spin_pass(arch_spinlock_t *ap, struct __raw_tickets inc);
> #define __TKT_SPIN_INC 2
>
> #else
>
> static inline bool tkt_spin_pass(arch_spinlock_t *ap, struct
> __raw_tickets inc)
> {
> return false;
> }
>
> #define __TKT_SPIN_INC 1
>
> #endif
>
> static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
> {
> register struct __raw_tickets inc = { .tail = __TKT_SPIN_INC };
>
> inc = xadd(&lock->tickets, inc);
>
> for (;;) {
> if (inc.head == inc.tail || tkt_spin_pass(lock, inc))
> break;
> cpu_relax();
> inc.head = ACCESS_ONCE(lock->tickets.head);
> }
> barrier; /* make sure nothing creeps before the lock is taken */
> }
>
> -- Steve
>
>
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