Comment 5 for bug 1789913

Hmm, still not much detail but here tis:

commit f79e5368512b72bb463925983d265b070261b7aa
Author: Jim Qu <email address hidden>
Date: Mon Aug 27 13:37:38 2018 +0800

    modesetting: code refactor for PRIME sync

    The X will be crashed on the system with other DDX driver,
    such as amdgpu.

    show the log like:

    randr: falling back to unsynchronized pixmap sharing
    (EE)
    (EE) Backtrace:
    (EE) 0: /usr/lib/xorg/Xorg (xorg_backtrace+0x4e)
    (EE) 1: /usr/lib/xorg/Xorg (0x55cb0151a000+0x1b5ce9)
    (EE) 2: /lib/x86_64-linux-gnu/libpthread.so.0 (0x7f1587a1d000+0x11390)
    (EE)
    (EE) Segmentation fault at address 0x0
    (EE)

    The issue is that modesetting as the master, and amdgpu as the slave.
    Thus, when the master attempts to access pSlavePixPriv in ms_dirty_update(),
    problems result due to the fact that it's accessing AMD's 'ppriv' using the
    modesetting structure definition.

    Apart from fixing crash issue, the patch fix other issue in master interface
    in which driver should refer to master pixmap.

    Signed-off-by: Jim Qu <email address hidden>
    Reviewed-by: Alex Goins <email address hidden>