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Trying to do a modeset from within a reset is fraught with danger. We can fall into a cyclic deadlock where the modeset is waiting on a previous modeset that is waiting on a request, and since the GPU hung that request completion is waiting on the reset. As modesetting doesn't allow its locks to be broken and restarted, or for its *own* reset mechanism to take over the display, we have to do something very evil instead. If we detect that we are stuck waiting to prepare the display reset (by using a very simple timeout), resort to cancelling all in-flight requests and throwing the user data into /dev/null, which is marginally better than the driver locking up and keeping that data to itself. This is not a fix; this is just a workaround that unbreaks machines until we can resolve the deadlock in a way that doesn't lose data! v2: Move the retirement from set-wegded to the i915_reset() error path, after which we no longer any delayed worker cleanup for i915_handle_error() v3: C abuse for syntactic sugar v4: Cover all waits with the timeout to catch more driver breakage References: https://bugs.freedesktop.org/show_bug.cgi?id=99093 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Mika Kuoppala <mika.kuoppala@intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20170622105625.16952-1-chris@chris-wilson.co.uk Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.