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

From: Tingwei Zhang <[email-masked]>
Date: Wed, 5 Aug 2020 10:54:39 +0800

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 <[email-masked]>
Tested-by: Mike Leach <[email-masked]>
---
 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);
+		}
 	}
+	if (!try_module_get(csdev->dev.parent->driver->owner))
+		goto err;
+	get_device(csdev->dev.parent);
 	pm_runtime_get_sync(csdev->dev.parent);
+	return 0;
+err:
+	for (i--; i >= 0; i--) {
+		struct coresight_device *child;
+
+		child  = csdev->pdata->conns[i].child_dev;
+		if (child && child->type == CORESIGHT_DEV_TYPE_HELPER) {
+			pm_runtime_put(child->dev.parent);
+			put_device(child->dev.parent);
+			module_put(child->dev.parent->driver->owner);
+		}
+	}
+	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);
 	for (i = 0; i < csdev->pdata->nr_outport; i++) {
 		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) {
 			pm_runtime_put(child->dev.parent);
+			put_device(child->dev.parent);
+			module_put(child->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);
 
-- 
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a Linux Foundation Collaborative Project

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