On 03/02/2013 06:44 PM, Lai Jiangshan wrote: > From 345a7a75c314ff567be48983e0892bc69c4452e7 Mon Sep 17 00:00:00 2001 > From: Lai Jiangshan <laijs@xxxxxxxxxxxxxx> > Date: Sat, 2 Mar 2013 20:33:14 +0800 > Subject: [PATCH] lglock: add read-preference local-global rwlock > > Current lglock is not read-preference, so it can't be used on some cases > which read-preference rwlock can do. Example, get_cpu_online_atomic(). > [...] > diff --git a/kernel/lglock.c b/kernel/lglock.c > index 6535a66..52e9b2c 100644 > --- a/kernel/lglock.c > +++ b/kernel/lglock.c > @@ -87,3 +87,71 @@ void lg_global_unlock(struct lglock *lg) > preempt_enable(); > } > EXPORT_SYMBOL(lg_global_unlock); > + > +#define FALLBACK_BASE (1UL << 30) > + > +void lg_rwlock_local_read_lock(struct lgrwlock *lgrw) > +{ > + struct lglock *lg = &lgrw->lglock; > + > + preempt_disable(); > + if (likely(!__this_cpu_read(*lgrw->reader_refcnt))) { > + rwlock_acquire_read(&lg->lock_dep_map, 0, 0, _RET_IP_); > + if (unlikely(!arch_spin_trylock(this_cpu_ptr(lg->lock)))) { > + read_lock(&lgrw->fallback_rwlock); > + __this_cpu_write(*lgrw->reader_refcnt, FALLBACK_BASE); > + return; > + } > + } > + > + __this_cpu_inc(*lgrw->reader_refcnt); > +} > +EXPORT_SYMBOL(lg_rwlock_local_read_lock); > + > +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; This should be a break, instead of a return, right? Otherwise, there will be a preempt imbalance... > + case FALLBACK_BASE: > + __this_cpu_write(*lgrw->reader_refcnt, 0); > + read_unlock(&lgrw->fallback_rwlock); > + rwlock_release(&lg->lock_dep_map, 1, _RET_IP_); > + break; > + default: > + __this_cpu_dec(*lgrw->reader_refcnt); > + break; > + } > + > + preempt_enable(); > +} Regards, Srivatsa S. Bhat -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html