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Owain Ainsworth reported an issue between the interaction of the hangcheck and userspace immediately (and permanently) falling back to s/w rasterisation. In order to break the mutex and begin resetting the GPU, we must abort the current operation (usually within the wait) and climb sufficiently far back up the call chain to drop the mutex. In his implementation, Owain has a loop within the ioctl handler to detect the hang and then sleep until the error handler has run. I've chosen to return to userspace and report an EAGAIN which should trigger the userspace ioctl handler to repeat the call (simply because it felt less invasive...). Before hitting a wedged GPU, we then wait upon completion of the error handler. Reported-by: Owain G. Ainsworth <zerooa@googlemail.com> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
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* For the very latest on DRI development, please see: *
* http://dri.freedesktop.org/ *
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The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).
The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:
1. The DRM provides synchronized access to the graphics hardware via
the use of an optimized two-tiered lock.
2. The DRM enforces the DRI security policy for access to the graphics
hardware by only allowing authenticated X11 clients access to
restricted regions of memory.
3. The DRM provides a generic DMA engine, complete with multiple
queues and the ability to detect the need for an OpenGL context
switch.
4. The DRM is extensible via the use of small device-specific modules
that rely extensively on the API exported by the DRM module.
Documentation on the DRI is available from:
http://dri.freedesktop.org/wiki/Documentation
http://sourceforge.net/project/showfiles.php?group_id=387
http://dri.sourceforge.net/doc/
For specific information about kernel-level support, see:
The Direct Rendering Manager, Kernel Support for the Direct Rendering
Infrastructure
http://dri.sourceforge.net/doc/drm_low_level.html
Hardware Locking for the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/hardware_locking_low_level.html
A Security Analysis of the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/security_low_level.html