Re: [PATCH v7 06/25] coresight: add try_get_module() in coresight_grab_device()

When coresight device is in an active session, driver module of
that device should not be removed. Use try_get_module() in
coresight_grab_device() to prevent module to be unloaded.
Use get_device()/put_device() to protect device data
in the middle of active session.

Signed-off-by: Tingwei Zhang <redacted>
Tested-by: Mike Leach <redacted>
---
  drivers/hwtracing/coresight/coresight.c | 39 +++++++++++++++++++++----
  1 file changed, 34 insertions(+), 5 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index b7151c5f81b1..1626bc885dfe 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c

@@ -640,7 +640,7 @@ struct coresight_device *coresight_get_sink_by_id(u32 id)
   * don't appear on the trace path, they should be handled along with the
   * the master device.
   */
-static void coresight_grab_device(struct coresight_device *csdev)
+static int coresight_grab_device(struct coresight_device *csdev)
  {
  	int i;
  

@@ -648,10 +648,30 @@ static void coresight_grab_device(struct coresight_device *csdev)
  		struct coresight_device *child;
  
  		child  = csdev->pdata->conns[i].child_dev;
-		if (child && child->type == CORESIGHT_DEV_TYPE_HELPER)
+		if (child && child->type == CORESIGHT_DEV_TYPE_HELPER) {
+			if (!try_module_get(child->dev.parent->driver->owner))
+				goto err;
+			get_device(child->dev.parent);
  			pm_runtime_get_sync(child->dev.parent);
+		}
  	}

+	}
+	return -ENODEV;
  }
  
  /*

@@ -663,12 +683,17 @@ static void coresight_drop_device(struct coresight_device *csdev)
  	int i;
  
  	pm_runtime_put(csdev->dev.parent);
+	put_device(csdev->dev.parent);
+	module_put(csdev->dev.parent->driver->owner);

  	}
  }
  

@@ -687,7 +712,7 @@ static int _coresight_build_path(struct coresight_device *csdev,
  				 struct coresight_device *sink,
  				 struct list_head *path)
  {
-	int i;
+	int i, ret;
  	bool found = false;
  	struct coresight_node *node;
  

@@ -721,7 +746,11 @@ static int _coresight_build_path(struct coresight_device *csdev,
  	if (!node)
  		return -ENOMEM;
  
-	coresight_grab_device(csdev);
+	ret = coresight_grab_device(csdev);
+	if (ret) {
+		kfree(node);
+		return ret;
+	}
  	node->csdev = csdev;
  	list_add(&node->link, path);