On 5/13/2014 7:58 AM, Grant Likely wrote:
> Make of_find_node_by_path() handle aliases as prefixes. To make this
> work the name search is refactored to search by path component instead
> of by full string. This should be a more efficient search, and it makes
> it possible to start a search at a subnode of a tree.
>
> Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>
> [grant.likely: Rework to not require allocating at runtime]
> Acked-by: Rob Herring <robh@xxxxxxxxxx>
> Signed-off-by: Grant Likely <grant.likely@xxxxxxxxxx>
> ---
> drivers/of/base.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 56 insertions(+), 4 deletions(-)
Was this patch created against a tree that has modifications to device tree
locking?
I get a hang due to deadlock when I apply it. Patch to verify the
cause is below.
From: Frank Rowand <frank.rowand@xxxxxxxxxxxxxx>
Do not apply this patch -- it is not a valid fix. The point of this patch
is to confirm the cause of a bug.
Problem seen on 3.15-rc1 with dragonboard platform patches added.
The dragonboard hangs on boot the very first time that of_find_node_by_path()
is called:
of_find_node_by_path()
raw_spin_lock_irqsave(&devtree_lock, flags)
np = __of_find_node_by_path(np, path)
for_each_child_of_node(parent, child) {
// This is a define:
#define for_each_child_of_node(parent, child) \
for (child = of_get_next_child(parent, NULL); child != NULL; \
// Resulting in a deadlock when of_get_next_child()
// attempts to lock the same lock:
raw_spin_lock_irqsave(&devtree_lock, flags)
When this patch is applied, the first lock is commented out so the
deadlock does not occur and the boot completes.
Not-signed-off-by: Frank Rowand <frank.rowand@xxxxxxxxxxxxxx>
---
drivers/of/base.c | 4 ++++
1 file changed, 4 insertions(+)
Index: b/drivers/of/base.c
===================================================================
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -835,13 +835,17 @@ struct device_node *of_find_node_by_path
}
/* Step down the tree matching path components */
+#if 0
raw_spin_lock_irqsave(&devtree_lock, flags);
+#endif
while (np && *path == '/') {
path++; /* Increment past '/' delimiter */
np = __of_find_node_by_path(np, path);
path = strchrnul(path, '/');
}
+#if 0
raw_spin_unlock_irqrestore(&devtree_lock, flags);
+#endif
return np;
}
EXPORT_SYMBOL(of_find_node_by_path);
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