On Sun, Mar 27, 2016 at 05:03:44AM -0700, Linus Torvalds wrote: > On Sun, Mar 27, 2016 at 1:57 AM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > > > I pulled ext4.git#dev on top of Linux v4.6-rc1... > > > > ... and did not see the call-trace. > > Unless you're using overlayfs or per-file encryption, I'm not seeing > that any of that should make any difference (but it's entirely > possible I'm missing something). > > Was it entirely repeatable before? Maybe it just happened to happen > without that update, and then happened to _not_ happen after you > rebooted with that 'dev' branch pulled in? > > Anyway, I don't think that DEBUG_LOCKS_WARN_ON() in > > kernel/locking/lockdep.c:2017 __lock_acquire > The code here is in check_no_collision(), so IIUC, there was a warning because a real chain_key collision happened. And chain_key is a hashsum of the ->class_idx of held_lock, calculated via iterate_chain_key(), and the ->class_idx of a held_lock may change from run to run IIUC, depending on the time register_lock_class() is called for the corresponding lock class. So this might be why Sedat didn't see the call-trace again. Of course, I may miss something subtle here, so add the author of check_no_collision() in CCs ;-) If I'm right, maybe we can provide more informative dmesg here rather than calling DEBUG_LOCKS_WARN_ON() directly? Regards, Boqun > would be an ext4 issue, it looks more like an internal lockdep issue. > > Adding in the lockdep people, who will set me right. > > Linus
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