of: fix recursive locking in of_get_next_available_child()

of_get_next_available_child() acquires devtree_lock, then calls of_device_is_available() which calls of_get_property() which calls of_find_property() which tries to re-acquire devtree_lock, thus causing deadlock. To avoid this, create a new __of_device_is_available() which calls __of_get_property() instead, which calls __of_find_property(), which does not take the lock,. Update of_get_next_available_child() to call the new __of_device_is_available() since it already owns the lock. Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

of: fix recursive locking in of_get_next_available_child()
of_get_next_available_child() acquires devtree_lock, then calls of_device_is_available() which calls of_get_property() which calls of_find_property() which tries to re-acquire devtree_lock, thus causing deadlock. To avoid this, create a new __of_device_is_available() which calls __of_get_property() instead, which calls __of_find_property(), which does not take the lock,. Update of_get_next_available_child() to call the new __of_device_is_available() since it already owns the lock. Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Stephen Warren · Grant Likely
1 parent bfc4a58986
Showing 1 changed file with 25 additions and 5 deletions Side-by-side Diff
drivers/of/base.c
@@ -290,19 +290,19 @@
 EXPORT_SYMBOL(of_machine_is_compatible);
  
 /**
- *  of_device_is_available - check if a device is available for use
+ *  __of_device_is_available - check if a device is available for use
  *
- *  @device: Node to check for availability
+ *  @device: Node to check for availability, with locks already held
  *
  *  Returns 1 if the status property is absent or set to "okay" or "ok",
  *  0 otherwise
  */
-int of_device_is_available(const struct device_node *device)
+static int __of_device_is_available(const struct device_node *device)
 {
 	const char *status;
 	int statlen;
  
-	status = of_get_property(device, "status", &statlen);
+	status = __of_get_property(device, "status", &statlen);
 	if (status == NULL)
 		return 1;
  
@@ -313,6 +313,26 @@
  
 	return 0;
 }
+
+/**
+ *  of_device_is_available - check if a device is available for use
+ *
+ *  @device: Node to check for availability
+ *
+ *  Returns 1 if the status property is absent or set to "okay" or "ok",
+ *  0 otherwise
+ */
+int of_device_is_available(const struct device_node *device)
+{
+	unsigned long flags;
+	int res;
+
+	raw_spin_lock_irqsave(&devtree_lock, flags);
+	res = __of_device_is_available(device);
+	raw_spin_unlock_irqrestore(&devtree_lock, flags);
+	return res;
+
+}
 EXPORT_SYMBOL(of_device_is_available);
  
 /**
@@ -404,7 +424,7 @@
 	raw_spin_lock(&devtree_lock);
 	next = prev ? prev->sibling : node->child;
 	for (; next; next = next->sibling) {
-		if (!of_device_is_available(next))
+		if (!__of_device_is_available(next))
 			continue;
 		if (of_node_get(next))
 			break;
...	...	@@ -290,19 +290,19 @@
290	290	EXPORT_SYMBOL(of_machine_is_compatible);
291	291
292	292	/**
293		- * of_device_is_available - check if a device is available for use
	293	+ * __of_device_is_available - check if a device is available for use
294	294	*
295		- * @device: Node to check for availability
	295	+ * @device: Node to check for availability, with locks already held
296	296	*
297	297	* Returns 1 if the status property is absent or set to "okay" or "ok",
298	298	* 0 otherwise
299	299	*/
300		-int of_device_is_available(const struct device_node *device)
	300	+static int __of_device_is_available(const struct device_node *device)
301	301	{
302	302	const char *status;
303	303	int statlen;
304	304
305		- status = of_get_property(device, "status", &statlen);
	305	+ status = __of_get_property(device, "status", &statlen);
306	306	if (status == NULL)
307	307	return 1;
308	308
...	...	@@ -313,6 +313,26 @@
313	313
314	314	return 0;
315	315	}
	316	+
	317	+/**
	318	+ * of_device_is_available - check if a device is available for use
	319	+ *
	320	+ * @device: Node to check for availability
	321	+ *
	322	+ * Returns 1 if the status property is absent or set to "okay" or "ok",
	323	+ * 0 otherwise
	324	+ */
	325	+int of_device_is_available(const struct device_node *device)
	326	+{
	327	+ unsigned long flags;
	328	+ int res;
	329	+
	330	+ raw_spin_lock_irqsave(&devtree_lock, flags);
	331	+ res = __of_device_is_available(device);
	332	+ raw_spin_unlock_irqrestore(&devtree_lock, flags);
	333	+ return res;
	334	+
	335	+}
316	336	EXPORT_SYMBOL(of_device_is_available);
317	337
318	338	/**
...	...	@@ -404,7 +424,7 @@
404	424	raw_spin_lock(&devtree_lock);
405	425	next = prev ? prev->sibling : node->child;
406	426	for (; next; next = next->sibling) {
407		- if (!of_device_is_available(next))
	427	+ if (!__of_device_is_available(next))
408	428	continue;
409	429	if (of_node_get(next))
410	430	break;