[Bug 101600] [BAT][PNV,BLB] i915_reset_device timed out, cancelling all in-flight rendering. provokes a dmesg-warn

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101600

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|WONTFIX                     |WORKSFORME

--- Comment #10 from Chris Wilson <chris at chris-wilson.co.uk> ---
dmesg spam be silenced (by avoiding the mutex deadlock in this and only this
scenario):

commit 8d52e447807b350b98ffb4e64bc2fcc1f181c5be
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Sat Jun 23 11:39:51 2018 +0100

    drm/i915: Defer modeset cleanup to a secondary task

    If we avoid cleaning up the old state immediately in
    intel_atomic_commit_tail() and defer it to a second task, we can avoid
    taking heavily contended locks when the caller is ready to procede.
    Subsequent modesets will wait for the cleanup operation (either directly
    via the ordered modeset wq or indirectly through the atomic helperr)
    which keeps the number of inflight cleanup tasks in check.

    As an example, during reset an immediate modeset is performed to disable
    the displays before the HW is reset, which must avoid struct_mutex to
    avoid recursion. Moving the cleanup to a separate task, defers acquiring
    the struct_mutex to after the GPU is running again, allowing it to
    complete. Even in a few patches time (optimist!) when we no longer
    require struct_mutex to unpin the framebuffers, it will still be good
    practice to minimise the number of contention points along reset. The
    mutex dependency still exists (as one modeset flushes the other), but in
    the short term it resolves the deadlock for simple reset cases.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101600
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Link:
https://patchwork.freedesktop.org/patch/msgid/20180623103951.23889-1-chris@chris-wilson.co.uk
    Acked-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
    Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>

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