3379c04cfa
For modern drivers the DRM core doesn't use struct_mutex at all, which
means it's defacto a driver-private lock. But since we still need it
for legacy drivers we can't initialize it in drivers, which means all
the different instances share one lockdep key. Despite that they might
be placed in totally different places in the locking hierarchy.
This results in a lot of bogus lockdep splats when running stuff on
systems with multiple gpus. Partially remedy the situation by only
doing might_lock checks on drivers that do use struct_mutex still for
gem locking.
A more complete solution would be to do the mutex_init in the drm core
only for legacy drivers, plus add it to each modern driver that still
needs it, which would also give each its own lockdep key. Trying to do
that dynamically doesn't work, because lockdep requires it's keys to
be statically allocated.
v2: {} everywhere (Chris)
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170715095328.25671-1-daniel.vetter@ffwll.ch
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.