drm/tegra: dc: Fix a potential race on page-flip completion

Page-flip completion could race with page-flip submission, so extend the
critical section to include all accesses to page-flip related data.

Reported-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index 5a6d43dfeb8d107e13ee2fe3b108b5669923bd29..ef36f9d5e35ee8b0a36691419567109f4846c563 100644 (file)
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -814,8 +814,12 @@ static void tegra_dc_finish_page_flip(struct tegra_dc *dc)
        unsigned long flags, base;
        struct tegra_bo *bo;
 
-       if (!dc->event)
+       spin_lock_irqsave(&drm->event_lock, flags);
+
+       if (!dc->event) {
+               spin_unlock_irqrestore(&drm->event_lock, flags);
                return;
+       }
 
        bo = tegra_fb_get_plane(crtc->primary->fb, 0);
 
@@ -825,12 +829,12 @@ static void tegra_dc_finish_page_flip(struct tegra_dc *dc)
        tegra_dc_writel(dc, 0, DC_CMD_STATE_ACCESS);
 
        if (base == bo->paddr + crtc->primary->fb->offsets[0]) {
-               spin_lock_irqsave(&drm->event_lock, flags);
                drm_crtc_send_vblank_event(crtc, dc->event);
                drm_crtc_vblank_put(crtc);
                dc->event = NULL;
-               spin_unlock_irqrestore(&drm->event_lock, flags);
        }
+
+       spin_unlock_irqrestore(&drm->event_lock, flags);
 }
 
 void tegra_dc_cancel_page_flip(struct drm_crtc *crtc, struct drm_file *file)