Peter Zijlstra wrote: > On Fri, Apr 06, 2018 at 09:04:18PM +0900, Tetsuo Handa wrote: > > + /* Temporary hack for handling lock imbalance. */ > > + if (__mutex_owner(&lo->lo_ctl_mutex) == current) > > + mutex_unlock(&lo->lo_ctl_mutex); > > ARGGH.. you didn't read the comment we put on that? >
Commit 5b52330bbfe63b33 ("audit: fix auditd/kernel connection state tracking") is using __mutex_owner(). ;-) Of course, regarding loop module, we will be able to add a flag variable associated with lo->lo_ctl_mutex. But that will be done after we solved the deadlock problem. I think whether we need to drop lo->lo_ctl_mutex is not clear. Maybe - err = mutex_lock_killable_nested(&lo->lo_ctl_mutex, 1); + err = mutex_lock_killable(&lo->lo_ctl_mutex); on top of this patch and listen to the lockdep? Commit f028f3b2f987ebc6 ("loop: fix circular locking in loop_clr_fd()") says A simple way to silence lockdep could be to mark the lo_ctl_mutex in ioctl to be a sub class, but this might mask some other real bugs. and we are currently hitting a deadlock problem.