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As we may unwind incomplete requests (for preemption) prior to processing the CSB and the schedule-out events, we may update rq->engine (resetting it to point back to the parent virtual engine) prior to calling execlists_schedule_out(), invalidating the assertion that the request still points to the inflight engine. (The likelihood of this is increased if the CSB interrupt processing is pushed to the ksoftirqd for being too slow and direct submission overtakes it.) Tvrtko summarised it as: "So unwind from direct submission resets rq->engine and races with process_csb from the tasklet which notices request has actually completed." Reported-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com> Fixes:df40306902("drm/i915/execlists: Lift process_csb() out of the irq-off spinlock") Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Vinay Belgaumkar <vinay.belgaumkar@intel.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190907105046.19934-1-chris@chris-wilson.co.uk (cherry picked from commitd810583fc2) Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
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.