[Bug 109605] [CI][SHARDS]: igt at gem_mmap_gtt@hang - incomplete/timeout - i915 0000:00:02.0: i915_reset_device timed out, cancelling all in-flight rendering.

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=109605

Martin Peres <martin.peres at free.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED

--- Comment #3 from Martin Peres <martin.peres at free.fr> ---
(In reply to Chris Wilson from comment #2)
> commit aeaaa55c7368ea0e7c195baa35dea37b806efb11
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date:   Tue Feb 12 13:08:30 2019 +0000
> 
>     drm/i915: Recursive i915_reset_trylock() verboten
>     
>     We cannot nest i915_reset_trylock() as the inner may wait for the
>     I915_RESET_BACKOFF which in turn is waiting upon sync_srcu who is
>     waiting for our outermost lock. As we take the reset srcu around the
>     fence update, we have to defer taking it in i915_gem_fault() until after
>     we acquire the pin on the fence to avoid nesting. This is a little ugly,
>     but still works. If a reset occurs between i915_vma_pin_fence() and the
>     second reset lock, the reset will restore the fence register back to the
>     pinned value before the reset lock allows us to proceed (our mmap won't
>     be revoked as we haven't yet marked it as being a userfault as that
>     requires us to hold the reset lock), so the pagefault is still
>     serialised with the revocation in reset.
>     
>     Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109605
>     Fixes: 2caffbf11762 ("drm/i915: Revoke mmaps and prevent access to fence
> registers across reset")
>     Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>     Cc: Mika Kuoppala <mika.kuoppala at intel.com>
>     Reviewed-by: Mika Kuoppala <mika.kuoppala at intel.com>
>     Link:
> https://patchwork.freedesktop.org/patch/msgid/20190212130831.14425-1-
> chris at chris-wilson.co.uk

10 runs without any issues, as opposed to multiple failures per run. Seems like
it was the right fix! Thanks!

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