drm_getclient, drm_getstats and drm_getmap (with a few minor
adjustments) do not need global mutex, so fix that and
make the said ioctls DRM_UNLOCKED. Details:
drm_getclient: the only thing that should be protected here
is dev->filelist and that is already protected everywhere with
dev->struct_mutex.
drm_getstats: there is no need for any mutex here because the
loop runs through quasi-static (set at load time only)
data, and the actual count access is done with atomic_read()
drm_getmap already uses dev->struct_mutex to protect
dev->maplist, which also used to protect the same structure
everywhere else except at three places:
* drm_getsarea, which doesn't grab *any* mutex before
touching dev->maplist (so no drm_global_mutex doesn't help
here either; different issue for a different patch).
However, drivers seem to call it only at
initialization time so it probably doesn't matter
* drm_master_destroy, which is called from drm_master_put,
which in turn is protected with dev->struct_mutex
everywhere else in drm module, so we are good here too.
* drm_getsareactx, which releases the dev->struct_mutex
too early, but this patch includes the fix for that.
v2: * incorporate comments received from Daniel Vetter
* include the (long) explanation above to make it clear what
we are doing (and why), also at Daniel Vetter's request
* tighten up mutex grab/release locations to only
encompass real critical sections, rather than some
random code around them
Signed-off-by: Ilija Hadzic <ihadzic@research.bell-labs.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
************************************************************
* For the very latest on DRI development, please see: *
* http://dri.freedesktop.org/ *
************************************************************
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
09b4ea47d1