Messages in this thread | | | Subject | Re: [PATCH RFC 02/12] x86/ticketlock: convert spin loop to C | From | Peter Zijlstra <> | Date | Mon, 02 Aug 2010 17:07:19 +0200 |
| |
On Fri, 2010-07-16 at 18:03 -0700, Jeremy Fitzhardinge wrote: > + register union { > + struct __raw_tickets tickets; > + unsigned short slock; > + } inc = { .slock = 1 << TICKET_SHIFT };
register arch_spinlock_t inc = { .tickets = { .head = 1, .tail = 0 } };
>From a quick look you can basically replace all TICKET_SHIFT usage (1 << TICKET_SHIFT) with such a constant.
[ Also, does gcc really listen to the register hint these days? ]
> + asm volatile (LOCK_PREFIX "xaddw %w0, %1\n" > + : "+Q" (inc), "+m" (lock->slock) : : "memory", "cc");
"+Q" (inc->slock)
> + for (;;) { > + if (inc.tickets.head == inc.tickets.tail) > + return; > + cpu_relax(); > + inc.tickets.head = ACCESS_ONCE(lock->tickets.head); > + } > + barrier(); /* make sure nothing creeps before the lock is taken */ > }
How will it ever get to that barrier() ?
| |