On 13/01/16 13:36, Imre Deak wrote:
On ke, 2016-01-13 at 12:46 +0000, Tvrtko Ursulin wrote:
On 11/01/16 16:56, Chris Wilson wrote:
On Mon, Jan 11, 2016 at 05:36:46PM +0200, Ville Syrjälä wrote:
On Mon, Jan 11, 2016 at 03:16:16PM +0000, Tvrtko Ursulin wrote:
Don't know, I leave this one to whoever grabbed the lock around
intel_init_gt_powersave in the first place. Maybe there was a
special
reason.. after git blame od intel_display.c eventually
completed, adding
Imre and Ville to cc.
Hmm. I don't recall the details anymore, but looking at the code
pushing
the locking down to valleyview_setup_pctx() looks entirely
reasonable to
me.
iirc, this locking only exists to keep the WARN() at bay. But it is
pedagogical, I guess.
Don't really know this area, but what about the
intel_gen6_powersave_work->valleyview_enable_rps-
valleyview_check_pctx
which dereferences the dev_priv->vlv_pctx, which is set/cleared in
valleyview_setup_pctx/valleyview_cleanup_pctx, which would now be
outside both struct_mutex and the rps lock?
dev_priv->vlv_pctx is not protected on the premise that the driver
init/cleanup functions can't race and gen6_powersave_work() is
scheduled only after intel_init_gt_powersave() and flushed
before intel_cleanup_gt_powersave().
rps_lock protects the RPS HW accesses themselves and struct_mutex was
taken for the GEM allocation. Taking it at high level around
intel_init_gt_powersave() was kind of a copy&paste in the commit you
found, there is more on that in 79f5b2c75992.
Thanks for digging this out.
It is more involved than what Chris pasted then, and while I hoped to be
able to quickly shove that into a patch, I cannot allow the time for
more the extensive analysis.
So my patch fixes the issue of struct_mutex not being held in
intel_alloc_initial_plane_obj while calling
i915_gem_object_create_stolen_for_preallocated and I'll leave
struct_mutex/rps.lock locking inversion in RPM to someone else.
Regards,
Tvrtko
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