Messages in this thread | | | Date | Sat, 2 Mar 2013 18:20:03 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH V2] lglock: add read-preference local-global rwlock |
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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.
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