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During igt_reset_nop_engine, it was observed that an unexpected failed engine reset lead to us busywaiting on the stop-ring semaphore (set during the reset preparations) on the first request afterwards. There was no explicit MI_ARB_CHECK in this sequence as the presumption was that the failed MI_SEMAPHORE_WAIT would itself act as an arbitration point. It did not in this circumstance, so force it. This patch is based on the assumption that the MI_SEMAPHORE_WAIT failure to arbitrate is a rare Tigerlake bug, similar to the lite-restore vs semaphore issues previously seen in the CS. The explicit MI_ARB_CHECK should always ensure that there is at least one arbitration point in the request before the MI_SEMAPHORE_WAIT to trigger the IDLE->ACTIVE event. Upon processing that event, we will clear the stop-ring flag and release the semaphore from its busywait. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20210112100759.32698-2-chris@chris-wilson.co.uk
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.
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.