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Date: Sat, 2 Mar 2013 18:20:03 +0100 From: Oleg Nesterov <oleg@...hat.com> To: Lai Jiangshan <laijs@...fujitsu.com> Cc: Michel Lespinasse <walken@...gle.com>, "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>, Lai Jiangshan <eag0628@...il.com>, linux-doc@...r.kernel.org, peterz@...radead.org, fweisbec@...il.com, linux-kernel@...r.kernel.org, namhyung@...nel.org, mingo@...nel.org, linux-arch@...r.kernel.org, linux@....linux.org.uk, xiaoguangrong@...ux.vnet.ibm.com, wangyun@...ux.vnet.ibm.com, paulmck@...ux.vnet.ibm.com, nikunj@...ux.vnet.ibm.com, linux-pm@...r.kernel.org, rusty@...tcorp.com.au, rostedt@...dmis.org, rjw@...k.pl, vincent.guittot@...aro.org, tglx@...utronix.de, linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org, sbw@....edu, tj@...nel.org, akpm@...ux-foundation.org, linuxppc-dev@...ts.ozlabs.org Subject: Re: [PATCH V2] lglock: add read-preference local-global rwlock On 03/02, Lai Jiangshan wrote: > > +void lg_rwlock_local_read_unlock(struct lgrwlock *lgrw) > +{ > + switch (__this_cpu_read(*lgrw->reader_refcnt)) { > + case 1: > + __this_cpu_write(*lgrw->reader_refcnt, 0); > + lg_local_unlock(&lgrw->lglock); > + return; > + case FALLBACK_BASE: > + __this_cpu_write(*lgrw->reader_refcnt, 0); > + read_unlock(&lgrw->fallback_rwlock); > + rwlock_release(&lg->lock_dep_map, 1, _RET_IP_); I guess "case 1:" should do rwlock_release() too. Otherwise, at first glance looks correct... However, I still think that FALLBACK_BASE only adds the unnecessary complications. But even if I am right this is subjective of course, please feel free to ignore. And btw, I am not sure about lg->lock_dep_map, perhaps we should use fallback_rwlock->dep_map ? We need rwlock_acquire_read() even in the fast-path, and this acquire_read should be paired with rwlock_acquire() in _write_lock(), but it does spin_acquire(lg->lock_dep_map). Yes, currently this is the same (afaics) but perhaps fallback_rwlock->dep_map would be more clean. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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