[PATCH] make attribute_container_unregister() unconditionally wait for list empty

[James Smart]

James,

>> > > Isn't a better way to handle it simply to give
>> > > transport_container_unregister() the semantics everyone is expecting
>> > > (i.e. to wait for everything to be tidied up and gone)?  That way none
>> > > of the transport classes needs updating, and we don't have to handle the
>> > > rather nasty release and unload races.
> 
> I was thinking of a wait_event driven system checking for 
> list_empty(cont->containers.k_list)

I hope this is more in line with what you were thinking.....

-- james s


Signed-off-by: James Smart <[EMAIL PROTECTED]>


diff -upNr a/drivers/base/attribute_container.c 
b/drivers/base/attribute_container.c
--- a/drivers/base/attribute_container.c        2007-08-16 02:59:50.000000000 
-0400
+++ b/drivers/base/attribute_container.c        2007-08-17 05:02:03.000000000 
-0400
@@ -19,6 +19,7 @@
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/sched.h>
 
 #include "base.h"
 
@@ -75,6 +76,8 @@ int
 attribute_container_register(struct attribute_container *cont)
 {
        INIT_LIST_HEAD(&cont->node);
+       init_waitqueue_head(&cont->cont_wait);
+       cont->flags &= ~ATTRIBUTE_CONTAINER_EVENT_PENDING;
        klist_init(&cont->containers,internal_container_klist_get,
                   internal_container_klist_put);
                
@@ -89,23 +92,26 @@ EXPORT_SYMBOL_GPL(attribute_container_re
 /**
  * attribute_container_unregister - remove a container registration
  *
+ * Semantics have now changed - we never return until the list goes empty
+ * 
  * @cont: previously registered container to remove
  */
 int
 attribute_container_unregister(struct attribute_container *cont)
 {
-       int retval = -EBUSY;
        mutex_lock(&attribute_container_mutex);
        spin_lock(&cont->containers.k_lock);
-       if (!list_empty(&cont->containers.k_list))
-               goto out;
-       retval = 0;
-       list_del(&cont->node);
- out:
+       if (!list_empty(&cont->containers.k_list)) 
+               cont->flags |= ATTRIBUTE_CONTAINER_EVENT_PENDING;
        spin_unlock(&cont->containers.k_lock);
        mutex_unlock(&attribute_container_mutex);
-       return retval;
-               
+       wait_event(cont->cont_wait,
+                        !(cont->flags & ATTRIBUTE_CONTAINER_EVENT_PENDING));
+       mutex_lock(&attribute_container_mutex);
+       list_del(&cont->node);
+       mutex_unlock(&attribute_container_mutex);
+
+       return 0;
 }
 EXPORT_SYMBOL_GPL(attribute_container_unregister);
 
@@ -234,6 +240,15 @@ attribute_container_remove_device(struct
                                class_device_unregister(&ic->classdev);
                        }
                }
+
+               if (cont->flags & ATTRIBUTE_CONTAINER_EVENT_PENDING) {
+                       spin_lock(&cont->containers.k_lock);
+                       if (list_empty(&cont->containers.k_list)) 
+                               cont->flags &= 
+                                       ~ATTRIBUTE_CONTAINER_EVENT_PENDING;
+                       spin_unlock(&cont->containers.k_lock);
+                       wake_up(&cont->cont_wait);
+               }
        }
        mutex_unlock(&attribute_container_mutex);
 }
diff -upNr a/include/linux/attribute_container.h 
b/include/linux/attribute_container.h
--- a/include/linux/attribute_container.h       2007-08-16 03:00:10.000000000 
-0400
+++ b/include/linux/attribute_container.h       2007-08-17 03:46:01.000000000 
-0400
@@ -20,7 +20,9 @@ struct attribute_container {
        struct class_device_attribute **attrs;
        int (*match)(struct attribute_container *, struct device *);
 #define        ATTRIBUTE_CONTAINER_NO_CLASSDEVS        0x01
+#define        ATTRIBUTE_CONTAINER_EVENT_PENDING       0x02
        unsigned long           flags;
+       wait_queue_head_t       cont_wait;
 };
 
 static inline int



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