drm/i915: don't set unpin_work if vblank_get fails

This fixes a race where we may try to finish a page flip and decrement
the refcount even if our vblank_get failed and we ended up with a
spurious flip pending interrupt.

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=34211.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index d544de9..91b5f87 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7189,11 +7189,16 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
        work->old_fb_obj = intel_fb->obj;
        INIT_WORK(&work->work, intel_unpin_work_fn);
 
+       ret = drm_vblank_get(dev, intel_crtc->pipe);
+       if (ret)
+               goto free_work;
+
        /* We borrow the event spin lock for protecting unpin_work */
        spin_lock_irqsave(&dev->event_lock, flags);
        if (intel_crtc->unpin_work) {
                spin_unlock_irqrestore(&dev->event_lock, flags);
                kfree(work);
+               drm_vblank_put(dev, intel_crtc->pipe);
 
                DRM_DEBUG_DRIVER("flip queue: crtc already busy\n");
                return -EBUSY;
@@ -7212,10 +7217,6 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 
        crtc->fb = fb;
 
-       ret = drm_vblank_get(dev, intel_crtc->pipe);
-       if (ret)
-               goto cleanup_objs;
-
        work->pending_flip_obj = obj;
 
        work->enable_stall_check = true;
@@ -7238,7 +7239,6 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 
 cleanup_pending:
        atomic_sub(1 << intel_crtc->plane, &work->old_fb_obj->pending_flip);
-cleanup_objs:
        drm_gem_object_unreference(&work->old_fb_obj->base);
        drm_gem_object_unreference(&obj->base);
        mutex_unlock(&dev->struct_mutex);
@@ -7247,6 +7247,8 @@ cleanup_objs:
        intel_crtc->unpin_work = NULL;
        spin_unlock_irqrestore(&dev->event_lock, flags);
 
+       drm_vblank_put(dev, intel_crtc->pipe);
+free_work:
        kfree(work);
 
        return ret;