Among other potential issues, this fixes a race between output polling
and status_show() that could cause a load detection false positive
with the nouveau driver.

Signed-off-by: Francisco Jerez <curroje...@riseup.net>
---
 drivers/gpu/drm/drm_sysfs.c |   71 ++++++++++++++++++++++++++++---------------
 1 files changed, 46 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index 85da4c4..25a9d9e 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -157,9 +157,13 @@ static ssize_t status_show(struct device *device,
                           char *buf)
 {
        struct drm_connector *connector = to_drm_connector(device);
+       struct drm_device *dev = connector->dev;
        enum drm_connector_status status;
 
+       mutex_lock(&dev->mode_config.mutex);
        status = connector->funcs->detect(connector, true);
+       mutex_unlock(&dev->mode_config.mutex);
+
        return snprintf(buf, PAGE_SIZE, "%s\n",
                        drm_get_connector_status_name(status));
 }
@@ -173,9 +177,11 @@ static ssize_t dpms_show(struct device *device,
        uint64_t dpms_status;
        int ret;
 
+       mutex_lock(&dev->mode_config.mutex);
        ret = drm_connector_property_get_value(connector,
                                            dev->mode_config.dpms_property,
                                            &dpms_status);
+       mutex_unlock(&dev->mode_config.mutex);
        if (ret)
                return 0;
 
@@ -199,25 +205,27 @@ static ssize_t edid_show(struct file *filp, struct 
kobject *kobj,
 {
        struct device *connector_dev = container_of(kobj, struct device, kobj);
        struct drm_connector *connector = to_drm_connector(connector_dev);
+       struct drm_device *dev = connector->dev;
        unsigned char *edid;
-       size_t size;
+       size_t size, n = 0;
 
+       mutex_lock(&dev->mode_config.mutex);
        if (!connector->edid_blob_ptr)
-               return 0;
+               goto out;
 
        edid = connector->edid_blob_ptr->data;
        size = connector->edid_blob_ptr->length;
        if (!edid)
-               return 0;
+               goto out;
 
        if (off >= size)
-               return 0;
-
-       if (off + count > size)
-               count = size - off;
-       memcpy(buf, edid + off, count);
+               goto out;
 
-       return count;
+       n = min(count, size - (size_t)off);
+       memcpy(buf, edid + off, n);
+out:
+       mutex_unlock(&dev->mode_config.mutex);
+       return n;
 }
 
 static ssize_t modes_show(struct device *device,
@@ -225,13 +233,16 @@ static ssize_t modes_show(struct device *device,
                           char *buf)
 {
        struct drm_connector *connector = to_drm_connector(device);
+       struct drm_device *dev = connector->dev;
        struct drm_display_mode *mode;
        int written = 0;
 
+       mutex_lock(&dev->mode_config.mutex);
        list_for_each_entry(mode, &connector->modes, head) {
                written += snprintf(buf + written, PAGE_SIZE - written, "%s\n",
                                    mode->name);
        }
+       mutex_unlock(&dev->mode_config.mutex);
 
        return written;
 }
@@ -245,7 +256,9 @@ static ssize_t subconnector_show(struct device *device,
        struct drm_property *prop = NULL;
        uint64_t subconnector;
        int is_tv = 0;
-       int ret;
+       int ret = 0;
+
+       mutex_lock(&dev->mode_config.mutex);
 
        switch (connector->connector_type) {
                case DRM_MODE_CONNECTOR_DVII:
@@ -260,21 +273,24 @@ static ssize_t subconnector_show(struct device *device,
                        break;
                default:
                        DRM_ERROR("Wrong connector type for this property\n");
-                       return 0;
+                       goto out;
        }
 
        if (!prop) {
                DRM_ERROR("Unable to find subconnector property\n");
-               return 0;
+               goto out;
        }
 
        ret = drm_connector_property_get_value(connector, prop, &subconnector);
        if (ret)
-               return 0;
+               goto out;
 
-       return snprintf(buf, PAGE_SIZE, "%s", is_tv ?
-                       drm_get_tv_subconnector_name((int)subconnector) :
-                       drm_get_dvi_i_subconnector_name((int)subconnector));
+       ret = snprintf(buf, PAGE_SIZE, "%s", is_tv ?
+                      drm_get_tv_subconnector_name((int)subconnector) :
+                      drm_get_dvi_i_subconnector_name((int)subconnector));
+out:
+       mutex_unlock(&dev->mode_config.mutex);
+       return ret;
 }
 
 static ssize_t select_subconnector_show(struct device *device,
@@ -286,7 +302,9 @@ static ssize_t select_subconnector_show(struct device 
*device,
        struct drm_property *prop = NULL;
        uint64_t subconnector;
        int is_tv = 0;
-       int ret;
+       int ret = 0;
+
+       mutex_lock(&dev->mode_config.mutex);
 
        switch (connector->connector_type) {
                case DRM_MODE_CONNECTOR_DVII:
@@ -301,21 +319,24 @@ static ssize_t select_subconnector_show(struct device 
*device,
                        break;
                default:
                        DRM_ERROR("Wrong connector type for this property\n");
-                       return 0;
+                       goto out;
        }
 
        if (!prop) {
                DRM_ERROR("Unable to find select subconnector property\n");
-               return 0;
+               goto out;
        }
 
        ret = drm_connector_property_get_value(connector, prop, &subconnector);
        if (ret)
-               return 0;
+               goto out;
 
-       return snprintf(buf, PAGE_SIZE, "%s", is_tv ?
-                       drm_get_tv_select_name((int)subconnector) :
-                       drm_get_dvi_i_select_name((int)subconnector));
+       ret = snprintf(buf, PAGE_SIZE, "%s", is_tv ?
+                      drm_get_tv_select_name((int)subconnector) :
+                      drm_get_dvi_i_select_name((int)subconnector));
+out:
+       mutex_unlock(&dev->mode_config.mutex);
+       return ret;
 }
 
 static struct device_attribute connector_attrs[] = {
-- 
1.6.4.4

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