drm/i915: Move drm_framebuffer_unreference out of struct_mutex for flips

intel_user_framebuffer_destroy() requires the struct_mutex for its
object bookkeeping, so this means that all calls to
drm_framebuffer_unreference must not hold that lock.

Regression from commit ab8d66752a9c28cd6c94fa173feacdfc1554aa03
Author: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Date:   Mon Feb 2 15:44:15 2015 +0000

    drm/i915: Track old framebuffer instead of object

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89166
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
[danvet: Clarify commit message slightly.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 70c95d3..75e8c8c 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9306,7 +9306,6 @@ static void intel_unpin_work_fn(struct work_struct *__work)
        mutex_lock(&dev->struct_mutex);
        intel_unpin_fb_obj(intel_fb_obj(work->old_fb));
        drm_gem_object_unreference(&work->pending_flip_obj->base);
-       drm_framebuffer_unreference(work->old_fb);
 
        intel_fbc_update(dev);
 
@@ -9315,6 +9314,7 @@ static void intel_unpin_work_fn(struct work_struct *__work)
        mutex_unlock(&dev->struct_mutex);
 
        intel_frontbuffer_flip_complete(dev, INTEL_FRONTBUFFER_PRIMARY(pipe));
+       drm_framebuffer_unreference(work->old_fb);
 
        BUG_ON(atomic_read(&to_intel_crtc(work->crtc)->unpin_work_count) == 0);
        atomic_dec(&to_intel_crtc(work->crtc)->unpin_work_count);
@@ -9978,10 +9978,6 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
        if (atomic_read(&intel_crtc->unpin_work_count) >= 2)
                flush_workqueue(dev_priv->wq);
 
-       ret = i915_mutex_lock_interruptible(dev);
-       if (ret)
-               goto cleanup;
-
        /* Reference the objects for the scheduled work. */
        drm_framebuffer_reference(work->old_fb);
        drm_gem_object_reference(&obj->base);
@@ -9991,6 +9987,10 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 
        work->pending_flip_obj = obj;
 
+       ret = i915_mutex_lock_interruptible(dev);
+       if (ret)
+               goto cleanup;
+
        atomic_inc(&intel_crtc->unpin_work_count);
        intel_crtc->reset_counter = atomic_read(&dev_priv->gpu_error.reset_counter);
 
@@ -10055,13 +10055,14 @@ cleanup_unpin:
        intel_unpin_fb_obj(obj);
 cleanup_pending:
        atomic_dec(&intel_crtc->unpin_work_count);
+       mutex_unlock(&dev->struct_mutex);
+cleanup:
        crtc->primary->fb = old_fb;
        update_state_fb(crtc->primary);
+
+       drm_gem_object_unreference_unlocked(&obj->base);
        drm_framebuffer_unreference(work->old_fb);
-       drm_gem_object_unreference(&obj->base);
-       mutex_unlock(&dev->struct_mutex);
 
-cleanup:
        spin_lock_irq(&dev->event_lock);
        intel_crtc->unpin_work = NULL;
        spin_unlock_irq(&dev->event_lock);