Messages in this thread |  | | | Subject | Re: [PATCH 06/20] x86/ticketlock: make __ticket_spin_trylock common | | From | Eric Dumazet <> | | Date | Sat, 13 Nov 2010 11:48:41 +0100 |
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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()
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