[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

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #2 from Chris Wilson <chris at chris-wilson.co.uk> ---
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@chris-wilson.co.uk

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