On Wed, Dec 8, 2010 at 2:49 AM, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> wrote: > On Wed, 2010-12-08 at 02:24 +1100, Nick Piggin wrote: >> >> repeat: >> spin_lock(&parent->d_lock); >> spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); >> /* do stuff */ >> spin_unlock(&parent->d_lock); >> spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_); >> parent = dentry; >> spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); >> goto repeat; > > shouldn't that be s/this_parent/parent/ ? Yes, typo in my pseudo code. > So what you're trying to do is: > > A -> B -> C -> ... > > lock A > lock B, nested > unlock A > flip B from nested to top > lock C, nested > unlock B > flip C from nested to top > lock ... > > Anyway, the way to write that is something like: > > lock_set_subclass(&detry->d_lock.dep_map, 0, _RET_IP_); > > Which will reset the subclass of the held lock from DENTRY_D_LOCK_NESTED > to 0. OK, thanks. My version should not have caused any problems though, right? Any idea what might have caused Dave's crash? > This is also used in double_unlock_balance(), we go into > double_lock_balance() with this_rq locked and want to lock busiest, > because of the lock ordering we might need to unlock this_rq and lock > busiest first, at which point this_rq is nested. > > On unlock we thus need to map this_rq back to subclass 0 (which it had > before double_lock_balance(), because otherwise subsequent lock > operations will be done against the subclass and confuse things. Thanks, Nick -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
