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[ Upstream commit2de42f79bb] Consider the following scenario: 1. nonblocking enable crtc 2. wait for the event 3. nonblocking disable crtc On i915 this can lead to a spurious -EBUSY from step 3 on account of non-enabled planes getting the fake_commit in step 1 and we don't complete the fake_commit-> flip_done until drm_atomic_helper_commit_hw_done() which can happen a long time after the flip event was sent out. This will become somewhat easy to hit on SKL+ once we start to add all the planes for the crtc to every modeset commit for the purposes of forcing a watermark register programming [1]. To make the race a little less pronounced let's complete fake_commit->flip_done after drm_atomic_helper_wait_for_flip_done(). For the single crtc case this should make the race quite theoretical, assuming drm_atomic_helper_wait_for_flip_done() actually has to wait for the real commit flip_done. In case the real commit flip_done gets completed singificantly before drm_atomic_helper_wait_for_flip_done(), or we are dealing with multiple crtcs whose vblanks don't line up nicely the race still exists. [1] https://patchwork.freedesktop.org/patch/262670/ Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Fixes:080de2e5be("drm/atomic: Check for busy planes/connectors before setting the commit") Testcase: igt/kms_cursor_legacy/*nonblocking-modeset-vs-cursor-atomic Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20181122143412.11655-1-ville.syrjala@linux.intel.com Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.