On 03/05/2013 09:11 PM, Lai Jiangshan wrote: > On 03/03/13 01:11, Srivatsa S. Bhat wrote: >> 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... > > > "lockdep" and "preempt" are handled in lg_local_unlock(&lgrw->lglock); > Ah, ok.. I had missed that. 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