[PATCH] devres: WARN() and return, don't crash on device_del() of uninitialized device

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

I just debugged an obscure crash caused by a device_del() of a all NULL'd
out struct device (in usb-serial) and found that a patch like this one would
have saved me time (in addition to improved chances of a bug report from
users hitting similar driver bugs).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

 drivers/base/devres.c |    5 +++++
 1 file changed, 5 insertions(+)

--- linux-work.orig/drivers/base/devres.c	2009-05-25 16:43:46.000000000 +1000
+++ linux-work/drivers/base/devres.c	2009-05-25 16:46:36.000000000 +1000
@@ -428,6 +428,11 @@ int devres_release_all(struct device *de
 {
 	unsigned long flags;
 
+	/* Looks like an uninitialized device structure */
+	if (dev->devres_head.next == NULL) {
+		WARN(1);
+		return -ENODEV;
+	}
 	spin_lock_irqsave(&dev->devres_lock, flags);
 	return release_nodes(dev, dev->devres_head.next, &dev->devres_head,
 			     flags);