On Fri, Feb 7, 2014 at 10:28 PM, Torsten Duwe <d...@lst.de> wrote:
> Ticket locks for ppc, version 2. Changes since v1:
> * The atomically exchanged entity is always 32 bits.
> * asm inline string variations thus removed.
> * Carry the additional holder hint only #if defined(CONFIG_PPC_SPLPAR)
>
> Signed-off-by: Torsten Duwe <d...@suse.de>
> --
[...]
> +static __always_inline void arch_spin_lock(arch_spinlock_t *lock)
> {
> + register struct __raw_tickets old, tmp,
> + inc = { .tail = TICKET_LOCK_INC };
> +
> CLEAR_IO_SYNC;
> - while (1) {
> - if (likely(__arch_spin_trylock(lock) == 0))
> - break;
> + __asm__ __volatile__(
> +"1: lwarx %0,0,%4 # arch_spin_lock\n"
> +" add %1,%3,%0\n"
> + PPC405_ERR77(0, "%4")
> +" stwcx. %1,0,%4\n"
> +" bne- 1b"
> + : "=&r" (old), "=&r" (tmp), "+m" (lock->tickets)
> + : "r" (inc), "r" (&lock->tickets)
> + : "cc");
> +
> + if (likely(old.head == old.tail))
> + goto out;
> +
> + for (;;) {
> + unsigned count = 100;
I am sure you wanted to tune the total loops to typical lock holding time ...
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