drm: make DRM_UNLOCKED ioctls with their own mutex
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>
3 files changed