[PATCH] work around deadlock in add_intf

[Martin Waitz]

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hi :)

the note for cpufreq sysfs support regarding locking in add_intf
has bitten me, too

i don't have a really good idea how to change the locking
so that it just works, so i wrote a workaround

the following patch allows to add interfaces again for me,
it just deferres the actual device additions:

--- src/linux-2.5/drivers/base/intf.c   Mon Jan 13 09:49:02 2003
+++ src/linux-rc/drivers/base/intf.c    Thu Jan 16 11:13:19 2003
@@ -132,6 +132,22 @@
=20
=20
 /**
+ *     delayed_add - version of add() called via schedule_work
+ *     @_data: pointer to arguments
+ */
+static void delayed_add(void *_data)
+{
+       struct {
+               struct device_interface *intf;
+               struct device *dev;
+               struct work_struct work;
+       } *data =3D _data;
+
+       add(data->intf, data->dev);
+       kfree(data);
+}
+
+/**
  *     add_intf - add class's devices to interface.
  *     @intf:  interface.
  *
@@ -142,12 +158,24 @@
  */
 static void add_intf(struct device_interface * intf)
 {
+       struct {
+               struct device_interface *intf;
+               struct device *dev;
+               struct work_struct work;
+       } *data;
        struct device_class * cls =3D intf->devclass;
        struct list_head * entry;
=20
        down_write(&cls->subsys.rwsem);
-       list_for_each(entry,&cls->devices.list)
-               add(intf,to_dev(entry));
+       list_for_each(entry,&cls->devices.list) {
+               /* add will lock subsys.rwsem via interface_add_data, */
+               /* do it after lock is released */
+               data =3D kmalloc(sizeof(*data), GFP_KERNEL);
+               INIT_WORK(&data->work, delayed_add, data);
+               data->intf =3D intf;
+               data->dev =3D to_dev(entry);
+               schedule_work(&data->work);
+       }
        up_write(&cls->subsys.rwsem);
 }
=20

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CU,		  / Friedrich-Alexander University Erlangen, Germany
Martin Waitz	//  [Tali on IRCnet]  [tali.home.pages.de] _________
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