On Wed, Apr 04, 2018 at 09:55:18AM -0400, Waiman Long wrote: > On 04/04/2018 09:23 AM, Theodore Y. Ts'o wrote: > > The commit 5149cbac4235: "locking/rwsem: Add DEBUG_RWSEMS to look for > > lock/unlock emismatches" (newly added in this merge window) will cause > > xfstests tests failures in generic/068 for all file systems. > > > > This is because the freeze and thaw ioctls, by design, are run in > > different processes. It looks like the concern for why > > CONFIG_DEBUG_RWSEMS was added is because read/write semaphores can > > spin --- which if the case, we need to make sure that (a) the spinlock > > code path is not used for the freeze/thaw ioctls, and (b) we don't > > trigger the debug WARN_ON. > > > > Cheers, > > > The rwsem code has an up_read_non_owner() function for this kind of > cross task lock/unlock. I think we should add the corresponding > up_write_non_owner() for that. Keep in mind this is a percpu_rwsem, not a rwsem. It's the sb_freeze_unlock() call in thaw_super() that is triggering it, and it would appear that percpu_rwsems have no concept on "non_owner" operation ATM. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
