On Tue, Nov 07, 2017 at 12:03:29PM +0800, Fengguang Wu wrote: > >>[ 428.512005] e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow > >>Control: RX > >>LKP: HOSTNAME vm-lkp-wsx03-openwrt-i386-8, MAC , kernel 4.14.0-rc8 158, > >>serial console /dev/ttyS0 > >>[ 429.798345] Kernel tests: Boot OK! > >>[ 430.761760] [ 430.766166] ===================================== > >>[ 430.775297] WARNING: bad unlock balance detected! > >>[ 430.784342] 4.14.0-rc8 #158 Not tainted > >>[ 430.792153] ------------------------------------- > >>[ 430.801319] pidof/1024 is trying to release lock (rcu_preempt_state) at: > >>[ 430.813514] [<c10e4348>] rcu_read_unlock_special+0x5f8/0x620 > >>[ 430.824041] but there are no more locks to release! > > > >Er... yes? What of that? Since when is rcu_read_lock() not allowed to > >be used under an rwsem?
That's not what it says, it is.. The warning is about trying to release a lock that's not held. And its right, RCU was doing that. It would acquire a lock without lockdep knowing about it and then telling lockdep about freeing it. This is fixed by commit: 02a7c234e540 ("rcu: Suppress lockdep false-positive ->boost_mtx complaints") The problem is that RCU boosting was mixing futex and !futex rt_mutex ops.