patches/of-fixup-resursive-locking-code-paths.patch

Subject: OF: Fixup resursive locking code paths
From: Paul Gortmaker <paul.gortmaker@windriver.com>
Date: Fri, 25 Jan 2013 13:21:47 -0500

From: Thomas Gleixner <tglx@linutronix.de>

There is no real reason to use a rwlock for devtree_lock. It even
could be a mutex, but unfortunately it's locked from cpu hotplug
paths which can't schedule :(

So it needs to become a raw lock on rt as well.  The devtree_lock would
be the only user of a raw_rw_lock, so we are better off cleaning up the
recursive locking paths which allows us to convert devtree_lock to a
read_lock.

Here we do the standard thing of introducing __foo() as the "raw"
version of foo(), so that we can take better control of the locking.
The "raw" versions are not exported and are for internal use within
the file itself.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: devicetree-discuss@lists.ozlabs.org
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Rob Herring <rob.herring@calxeda.com>
Link: http://lkml.kernel.org/r/1359138107-14159-1-git-send-email-paul.gortmaker@windriver.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---

[This has been living in the RT tree for several releases, and I've
 put it on top of 3.8-rc4 mainline and tested it independently there
 on a ppc sbc8548 board as well.  So it would be nice to get this in 3.9]

 drivers/of/base.c |   91 +++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 70 insertions(+), 21 deletions(-)

--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -164,16 +164,14 @@ void of_node_put(struct device_node *nod
 EXPORT_SYMBOL(of_node_put);
 #endif /* CONFIG_OF_DYNAMIC */
 
-struct property *of_find_property(const struct device_node *np,
-				  const char *name,
-				  int *lenp)
+static struct property *__of_find_property(const struct device_node *np,
+					   const char *name, int *lenp)
 {
 	struct property *pp;
 
 	if (!np)
 		return NULL;
 
-	read_lock(&devtree_lock);
 	for (pp = np->properties; pp; pp = pp->next) {
 		if (of_prop_cmp(pp->name, name) == 0) {
 			if (lenp)
@@ -181,6 +179,18 @@ struct property *of_find_property(const
 			break;
 		}
 	}
+
+	return pp;
+}
+
+struct property *of_find_property(const struct device_node *np,
+				  const char *name,
+				  int *lenp)
+{
+	struct property *pp;
+
+	read_lock(&devtree_lock);
+	pp = __of_find_property(np, name, lenp);
 	read_unlock(&devtree_lock);
 
 	return pp;
@@ -214,8 +224,20 @@ EXPORT_SYMBOL(of_find_all_nodes);
  * Find a property with a given name for a given node
  * and return the value.
  */
+static const void *__of_get_property(const struct device_node *np,
+				     const char *name, int *lenp)
+{
+	struct property *pp = __of_find_property(np, name, lenp);
+
+	return pp ? pp->value : NULL;
+}
+
+/*
+ * Find a property with a given name for a given node
+ * and return the value.
+ */
 const void *of_get_property(const struct device_node *np, const char *name,
-			 int *lenp)
+			    int *lenp)
 {
 	struct property *pp = of_find_property(np, name, lenp);
 
@@ -226,13 +248,13 @@ EXPORT_SYMBOL(of_get_property);
 /** Checks if the given "compat" string matches one of the strings in
  * the device's "compatible" property
  */
-int of_device_is_compatible(const struct device_node *device,
-		const char *compat)
+static int __of_device_is_compatible(const struct device_node *device,
+				     const char *compat)
 {
 	const char* cp;
 	int cplen, l;
 
-	cp = of_get_property(device, "compatible", &cplen);
+	cp = __of_get_property(device, "compatible", &cplen);
 	if (cp == NULL)
 		return 0;
 	while (cplen > 0) {
@@ -245,6 +267,20 @@ int of_device_is_compatible(const struct
 
 	return 0;
 }
+
+/** Checks if the given "compat" string matches one of the strings in
+ * the device's "compatible" property
+ */
+int of_device_is_compatible(const struct device_node *device,
+		const char *compat)
+{
+	int res;
+
+	read_lock(&devtree_lock);
+	res = __of_device_is_compatible(device, compat);
+	read_unlock(&devtree_lock);
+	return res;
+}
 EXPORT_SYMBOL(of_device_is_compatible);
 
 /**
@@ -518,7 +554,8 @@ struct device_node *of_find_compatible_n
 		if (type
 		    && !(np->type && (of_node_cmp(np->type, type) == 0)))
 			continue;
-		if (of_device_is_compatible(np, compatible) && of_node_get(np))
+		if (__of_device_is_compatible(np, compatible) &&
+		    of_node_get(np))
 			break;
 	}
 	of_node_put(from);
@@ -562,15 +599,9 @@ out:
 }
 EXPORT_SYMBOL(of_find_node_with_property);
 
-/**
- * of_match_node - Tell if an device_node has a matching of_match structure
- *	@matches:	array of of device match structures to search in
- *	@node:		the of device structure to match against
- *
- *	Low level utility function used by device matching.
- */
-const struct of_device_id *of_match_node(const struct of_device_id *matches,
-					 const struct device_node *node)
+static
+const struct of_device_id *__of_match_node(const struct of_device_id *matches,
+					   const struct device_node *node)
 {
 	if (!matches)
 		return NULL;
@@ -584,14 +615,32 @@ const struct of_device_id *of_match_node
 			match &= node->type
 				&& !strcmp(matches->type, node->type);
 		if (matches->compatible[0])
-			match &= of_device_is_compatible(node,
-						matches->compatible);
+			match &= __of_device_is_compatible(node,
+							   matches->compatible);
 		if (match)
 			return matches;
 		matches++;
 	}
 	return NULL;
 }
+
+/**
+ * of_match_node - Tell if an device_node has a matching of_match structure
+ *	@matches:	array of of device match structures to search in
+ *	@node:		the of device structure to match against
+ *
+ *	Low level utility function used by device matching.
+ */
+const struct of_device_id *of_match_node(const struct of_device_id *matches,
+					 const struct device_node *node)
+{
+	const struct of_device_id *match;
+
+	read_lock(&devtree_lock);
+	match = __of_match_node(matches, node);
+	read_unlock(&devtree_lock);
+	return match;
+}
 EXPORT_SYMBOL(of_match_node);
 
 /**
@@ -619,7 +668,7 @@ struct device_node *of_find_matching_nod
 	read_lock(&devtree_lock);
 	np = from ? from->allnext : of_allnodes;
 	for (; np; np = np->allnext) {
-		if (of_match_node(matches, np) && of_node_get(np)) {
+		if (__of_match_node(matches, np) && of_node_get(np)) {
 			if (match)
 				*match = matches;
 			break;