dahdi_dynamic: Remove calls to __module_get().

The board drivers are the ones calling the unregister function, and
therefore we do not need to worry about them unloading while calling the
destroy callback.

When destroying spans with the ioctl, replace __module_get() with
try_module_get. This avoids hitting a BUG in module_get on kernel versions <
2.6.29.

ALSO move the call to try_module_get out of the dahdi_dynamic_release function
and into destroy. This way if the destroy callback isn't called because the
dynamic driver is unloading the dynamic device can be left on the list to be
cleaned up by the dahdi_dynamic_unregister_driver function().

Signed-off-by: Shaun Ruffell <sruffell@digium.com>

Origin: http://svnview.digium.com/svn/dahdi?view=rev&rev=10624

git-svn-id: http://svn.asterisk.org/svn/dahdi/linux/branches/2.6@10629 a0bf4364-ded3-4de4-8d8a-66a801d63aff

1 files changed, 21 insertions, 15 deletions

diff --git a/drivers/dahdi/dahdi_dynamic.c b/drivers/dahdi/dahdi_dynamic.c
index 832e283..ba6b68e 100644
--- a/drivers/dahdi/dahdi_dynamic.c
+++ b/drivers/dahdi/dahdi_dynamic.c
@@ -385,16 +385,6 @@ static void dahdi_dynamic_release(struct kref *kref)
 
 	WARN_ON(test_bit(DAHDI_FLAGBIT_REGISTERED, &d->span.flags));
 
-	if (d->pvt) {
-		if (d->driver && d->driver->destroy) {
-			__module_get(d->driver->owner);
-			d->driver->destroy(d);
-			module_put(d->driver->owner);
-		} else {
-			WARN_ON(1);
-		}
-	}
-
 	kfree(d->msgbuf);
 
 	for (x = 0; x < d->span.channels; x++)
@@ -470,6 +460,24 @@ static int _destroy_dynamic(struct dahdi_dynamic_span *dds)
 		return -EBUSY;
 	}
 
+	if (d->pvt) {
+		if (d->driver && d->driver->destroy) {
+			if (!try_module_get(d->driver->owner)) {
+				/* The driver for this device is in the
+				 * process of unloading. Leave this dynamic on
+				 * the list so it's cleaned up when the driver
+				 * unregisters. */
+				 dynamic_put(d);
+				 return -ENXIO;
+			}
+			d->driver->destroy(d);
+			module_put(d->driver->owner);
+		} else {
+			WARN_ON(1);
+		}
+		d->pvt = NULL;
+	}
+
 	dahdi_unregister_device(d->ddev);
 
 	spin_lock_irqsave(&dspan_lock, flags);
@@ -767,19 +775,17 @@ void dahdi_dynamic_unregister_driver(struct dahdi_dynamic_driver *dri)
 	list_for_each_entry_safe(d, n, &dspan_list, list) {
 		if (d->driver == dri) {
 			if (d->pvt) {
-				if (d->driver && d->driver->destroy) {
-					__module_get(d->driver->owner);
+				if (d->driver && d->driver->destroy)
 					d->driver->destroy(d);
-					module_put(d->driver->owner);
-				} else {
+				else
 					WARN_ON(1);
-				}
 			}
 			dahdi_unregister_device(d->ddev);
 			spin_lock_irqsave(&dspan_lock, flags);
 			list_del_rcu(&d->list);
 			spin_unlock_irqrestore(&dspan_lock, flags);
 			synchronize_rcu();
+			d->driver = NULL;
 			dynamic_put(d);
 		}
 	}