Messages in this thread | | | Date | Mon, 15 Nov 2010 11:39:03 -0800 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH 06/20] x86/ticketlock: make __ticket_spin_trylock common |
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On 11/13/2010 02:48 AM, Eric Dumazet wrote: > Le samedi 13 novembre 2010 à 18:17 +0800, Américo Wang a écrit : >> On Wed, Nov 03, 2010 at 10:59:47AM -0400, Jeremy Fitzhardinge wrote: >> >>> + union { >>> + struct __raw_tickets tickets; >>> + __ticketpair_t slock; >>> + } tmp, new; >>> + int ret; >>> + >>> + tmp.tickets = ACCESS_ONCE(lock->tickets); >>> + if (tmp.tickets.head != tmp.tickets.tail) >>> + return 0; >>> + >>> + new.slock = tmp.slock + (1 << TICKET_SHIFT); >>> + >>> + ret = cmpxchg(&lock->ticketpair, tmp.slock, new.slock) == tmp.slock; >>> + barrier(); /* just make nothing creeps before lock is claimed */ >> This one should be smp_wmb(), right? No CONFIG_X86_OOSTORE protected. > cmpxchg() is a full memory barrier, no need for smp_wmb() or barrier()
Agreed.
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