[Bug 104209] [CI] igt at gem_userptr_blits@map-fixed-invalidate-gup - dmesg-warn: WARNING: possible circular locking dependency detected

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=104209

--- Comment #3 from Daniel Vetter <daniel at ffwll.ch> ---
Repeating my analysis from the mail thread: This looks real:

https://www.spinics.net/lists/intel-gfx/msg150141.html

In both cases of the circle we seem to hit exactly the same gtt/drm_device
mapping locks. One way to break this is to make sure we do not call
flush_workqueue on a range which isn't userptr-mapped (which automatically
avoids gtt mmaps, since those are not allowed for userptr, or at least should).
That option still has the classification problem, and I'm honestly not sure
it's actually deadlock-free.

Or we have to somehow get rid of the flush_work from the mmu_notifier callback
entirely. Safest option, but I dunno how right now.

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