Re: [PATCH] of: Fix locking when calling of_get_next_available_child()

Rob Herring
2013-02-11T22:28:04Z

On 02/11/2013 04:19 PM, Grant Likely wrote:
> of_get_next_available_child() obtains the devtree_lock and then calls
> of_device_is_available() which also attempts to claim the lock. This is
> obviously incorrect and causes a deadlock on boot. Fix issue by adding
> an variant of of_device_is_available() which doesn't obtain the lock.
>
> Cc: Stephen Warren <swarren@wwwdotorg.org>
> Cc: Rob Herring <robherring2@gmail.com>
> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
> ---
> drivers/of/base.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index e8d65af..4af74b7 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -297,7 +297,7 @@ EXPORT_SYMBOL(of_machine_is_compatible);
> * 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)
> +int __of_device_is_available(const struct device_node *device)
> {
> const char *status;
> int statlen;
> @@ -313,6 +313,17 @@ int of_device_is_available(const struct device_node *device)
>
> return 0;
> }
> +
> +int of_device_is_available(const struct device_node *device)

Stephen's version wins because he preserved the documentation. :)

Rob

> +{
> + unsigned long flags;
> + int rc;
> +
> + raw_spin_lock_irqsave(&devtree_lock, flags);
> + rc = __of_device_is_available(device);
> + raw_spin_unlock_irqrestore(&devtree_lock, flags);
> + return rc;
> +}
> EXPORT_SYMBOL(of_device_is_available);
>
> /**
> @@ -404,7 +415,7 @@ struct device_node *of_get_next_available_child(const struct device_node *node,
> 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;
>