[7/7] drm/i915: GEM operations need to be done under the big lock
diff mbox

Message ID 1452521321-4032-8-git-send-email-tvrtko.ursulin@linux.intel.com
State New
Headers show

Commit Message

Tvrtko Ursulin Jan. 11, 2016, 2:08 p.m. UTC
From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

VMA creation and GEM list management need the big lock.

v2:

Mutex unlock ended on the wrong path somehow. (0-day, Julia Lawall)

Not to mention drm_gem_object_unreference was there in existing
code with no mutex held.

v3:

Some callers of i915_gem_object_create_stolen_for_preallocated
already hold the lock so move the mutex into the other caller
as well.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/i915_gem_stolen.c | 3 +++
 drivers/gpu/drm/i915/intel_display.c   | 8 ++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

Comments

Chris Wilson Jan. 11, 2016, 2:38 p.m. UTC | #1
On Mon, Jan 11, 2016 at 02:08:41PM +0000, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> 
> VMA creation and GEM list management need the big lock.
> 
> v2:
> 
> Mutex unlock ended on the wrong path somehow. (0-day, Julia Lawall)
> 
> Not to mention drm_gem_object_unreference was there in existing
> code with no mutex held.
> 
> v3:
> 
> Some callers of i915_gem_object_create_stolen_for_preallocated
> already hold the lock so move the mutex into the other caller
> as well.

intel_pm.c valleyview_setup_pctx?
-Chris
Tvrtko Ursulin Jan. 11, 2016, 2:47 p.m. UTC | #2
On 11/01/16 14:38, Chris Wilson wrote:
> On Mon, Jan 11, 2016 at 02:08:41PM +0000, Tvrtko Ursulin wrote:
>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>
>> VMA creation and GEM list management need the big lock.
>>
>> v2:
>>
>> Mutex unlock ended on the wrong path somehow. (0-day, Julia Lawall)
>>
>> Not to mention drm_gem_object_unreference was there in existing
>> code with no mutex held.
>>
>> v3:
>>
>> Some callers of i915_gem_object_create_stolen_for_preallocated
>> already hold the lock so move the mutex into the other caller
>> as well.
>
> intel_pm.c valleyview_setup_pctx?

Already holds it traced by the WARN_ON at its top.

Regards,

Tvrtko
Chris Wilson Jan. 11, 2016, 3 p.m. UTC | #3
On Mon, Jan 11, 2016 at 02:47:17PM +0000, Tvrtko Ursulin wrote:
> 
> On 11/01/16 14:38, Chris Wilson wrote:
> >On Mon, Jan 11, 2016 at 02:08:41PM +0000, Tvrtko Ursulin wrote:
> >>From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> >>
> >>VMA creation and GEM list management need the big lock.
> >>
> >>v2:
> >>
> >>Mutex unlock ended on the wrong path somehow. (0-day, Julia Lawall)
> >>
> >>Not to mention drm_gem_object_unreference was there in existing
> >>code with no mutex held.
> >>
> >>v3:
> >>
> >>Some callers of i915_gem_object_create_stolen_for_preallocated
> >>already hold the lock so move the mutex into the other caller
> >>as well.
> >
> >intel_pm.c valleyview_setup_pctx?
> 
> Already holds it traced by the WARN_ON at its top.

Which is a nice little mutex inversion of its own. :|
i.e. rpm vs struct_mutex bug
-Chris

Patch
diff mbox

diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
index c384dc9c8a63..a97a5e762c0f 100644
--- a/drivers/gpu/drm/i915/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
@@ -635,6 +635,9 @@  i915_gem_object_create_stolen_for_preallocated(struct drm_device *dev,
 	if (!drm_mm_initialized(&dev_priv->mm.stolen))
 		return NULL;
 
+	if (WARN_ON_ONCE(!mutex_is_locked(&dev->struct_mutex)))
+		return NULL;
+
 	DRM_DEBUG_KMS("creating preallocated stolen object: stolen_offset=%x, gtt_offset=%x, size=%x\n",
 			stolen_offset, gtt_offset, size);
 
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index b4cf9ce16155..073d6c99406b 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2534,12 +2534,16 @@  intel_alloc_initial_plane_obj(struct intel_crtc *crtc,
 	if (size_aligned * 2 > dev_priv->gtt.stolen_usable_size)
 		return false;
 
+	mutex_lock(&dev->struct_mutex);
+
 	obj = i915_gem_object_create_stolen_for_preallocated(dev,
 							     base_aligned,
 							     base_aligned,
 							     size_aligned);
-	if (!obj)
+	if (!obj) {
+		mutex_unlock(&dev->struct_mutex);
 		return false;
+	}
 
 	obj->tiling_mode = plane_config->tiling;
 	if (obj->tiling_mode == I915_TILING_X)
@@ -2552,12 +2556,12 @@  intel_alloc_initial_plane_obj(struct intel_crtc *crtc,
 	mode_cmd.modifier[0] = fb->modifier[0];
 	mode_cmd.flags = DRM_MODE_FB_MODIFIERS;
 
-	mutex_lock(&dev->struct_mutex);
 	if (intel_framebuffer_init(dev, to_intel_framebuffer(fb),
 				   &mode_cmd, obj)) {
 		DRM_DEBUG_KMS("intel fb init failed\n");
 		goto out_unref_obj;
 	}
+
 	mutex_unlock(&dev->struct_mutex);
 
 	DRM_DEBUG_KMS("initial plane fb obj %p\n", obj);