[Intel-gfx] [PATCH 3/5] drm/i915: Remove struct_mutex for destroying framebuffers

[Chris Wilson]

We do not need to hold struct_mutex for destroying drm_i915_gem_objects
any longer, and with a little care taken over tracking
obj->framebuffer_references, we can relinquish BKL locking around the
destroy of intel_framebuffer.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.h          |  2 +-
 drivers/gpu/drm/i915/i915_gem_shrinker.c |  2 +-
 drivers/gpu/drm/i915/i915_gem_tiling.c   |  2 +-
 drivers/gpu/drm/i915/intel_display.c     | 10 +++++-----
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 30777dee3f9c..1b42fa9145a0 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2328,7 +2328,7 @@ struct drm_i915_gem_object {
        struct reservation_object *resv;
 
        /** References from framebuffers, locks out tiling changes. */
-       unsigned long framebuffer_references;
+       atomic_t framebuffer_references;
 
        /** Record of address bit 17 of each page at last unbind. */
        unsigned long *bit_17;
diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c 
b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index a6fc1bdc48af..3e6eabde1827 100644
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -216,7 +216,7 @@ i915_gem_shrink(struct drm_i915_private *dev_priv,
 
                        if (!(flags & I915_SHRINK_ACTIVE) &&
                            (i915_gem_object_is_active(obj) ||
-                            obj->framebuffer_references))
+                            atomic_read(&obj->framebuffer_references)))
                                continue;
 
                        if (!can_release_pages(obj))
diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c 
b/drivers/gpu/drm/i915/i915_gem_tiling.c
index 251d51b01174..07531c350ef2 100644
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -206,7 +206,7 @@ i915_gem_set_tiling(struct drm_device *dev, void *data,
        }
 
        mutex_lock(&dev->struct_mutex);
-       if (obj->pin_display || obj->framebuffer_references) {
+       if (obj->pin_display || atomic_read(&obj->framebuffer_references)) {
                err = -EBUSY;
                goto err;
        }
diff --git a/drivers/gpu/drm/i915/intel_display.c 
b/drivers/gpu/drm/i915/intel_display.c
index 318d0002d2ca..9274386fba31 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15664,14 +15664,14 @@ static void intel_setup_outputs(struct drm_device 
*dev)
 
 static void intel_user_framebuffer_destroy(struct drm_framebuffer *fb)
 {
-       struct drm_device *dev = fb->dev;
        struct intel_framebuffer *intel_fb = to_intel_framebuffer(fb);
 
        drm_framebuffer_cleanup(fb);
-       mutex_lock(&dev->struct_mutex);
-       WARN_ON(!intel_fb->obj->framebuffer_references--);
+
+       WARN_ON(atomic_read(&intel_fb->obj->framebuffer_references) == 0);
+       atomic_dec(&intel_fb->obj->framebuffer_references);
        i915_gem_object_put(intel_fb->obj);
-       mutex_unlock(&dev->struct_mutex);
+
        kfree(intel_fb);
 }
 
@@ -15916,7 +15916,7 @@ static int intel_framebuffer_init(struct drm_device 
*dev,
                return ret;
        }
 
-       intel_fb->obj->framebuffer_references++;
+       atomic_inc(&intel_fb->obj->framebuffer_references);
 
        return 0;
 }
-- 
2.10.2

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