drm/msm/atomic: Drop per-CRTC locks in reverse order

lockdep dislikes seeing locks unwound in a non-nested fashion.

Fixes: b3d91800d9ac ("drm/msm: Fix race condition in msm driver with async layer updates")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>

diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c
index 575e9af9b6fc9b3a2158747e5fa8bc3f06091944..93d39608a073983d3008475165522e6f6fbeb554 100644 (file)
--- a/drivers/gpu/drm/msm/msm_atomic.c
+++ b/drivers/gpu/drm/msm/msm_atomic.c
@@ -67,7 +67,7 @@ static void unlock_crtcs(struct msm_kms *kms, unsigned int crtc_mask)
 {
        struct drm_crtc *crtc;
 
-       for_each_crtc_mask(kms->dev, crtc, crtc_mask)
+       for_each_crtc_mask_reverse(kms->dev, crtc, crtc_mask)
                mutex_unlock(&kms->commit_lock[drm_crtc_index(crtc)]);
 }
 

diff --git a/drivers/gpu/drm/msm/msm_kms.h b/drivers/gpu/drm/msm/msm_kms.h
index 2049847b66428cc4b1a88a4cec3bb3644a65ab90..977ea96e383bb1ecec411541b62d68f936ca2996 100644 (file)
--- a/drivers/gpu/drm/msm/msm_kms.h
+++ b/drivers/gpu/drm/msm/msm_kms.h
@@ -196,4 +196,8 @@ int dpu_mdss_init(struct drm_device *dev);
        drm_for_each_crtc(crtc, dev) \
                for_each_if (drm_crtc_mask(crtc) & (crtc_mask))
 
+#define for_each_crtc_mask_reverse(dev, crtc, crtc_mask) \
+       drm_for_each_crtc_reverse(crtc, dev) \
+               for_each_if (drm_crtc_mask(crtc) & (crtc_mask))
+
 #endif /* __MSM_KMS_H__ */

diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 59b51a09cae6b8683e0b9abafe9560c145d74dac..cd42f79b28909b4776960814ed3ebbe884fcbd81 100644 (file)
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -1266,4 +1266,14 @@ static inline struct drm_crtc *drm_crtc_find(struct drm_device *dev,
 #define drm_for_each_crtc(crtc, dev) \
        list_for_each_entry(crtc, &(dev)->mode_config.crtc_list, head)
 
+/**
+ * drm_for_each_crtc_reverse - iterate over all CRTCs in reverse order
+ * @crtc: a &struct drm_crtc as the loop cursor
+ * @dev: the &struct drm_device
+ *
+ * Iterate over all CRTCs of @dev.
+ */
+#define drm_for_each_crtc_reverse(crtc, dev) \
+       list_for_each_entry_reverse(crtc, &(dev)->mode_config.crtc_list, head)
+
 #endif /* __DRM_CRTC_H__ */