[PATCH 1/4] Task notifier: Allow the removal of a notifier from the notifier handler

[Christoph Lameter <christoph@lameter.com>]

Allow a notifier to remove itself from the notifier list.

This is done by retrieving the pointer to the next notifier from the list before the
notifier call. If a notifier removes itself in the current kernel then the 
pointer to the current notifier is invalid and notifier_call_chain 
will fail.

Signed-off-by: Christoph Lameter <christoph@lameter.com>

Index: linux-2.6.13-rc3/kernel/sys.c
===================================================================
--- linux-2.6.13-rc3.orig/kernel/sys.c	2005-07-12 21:46:46.000000000 -0700
+++ linux-2.6.13-rc3/kernel/sys.c	2005-07-28 11:26:00.000000000 -0700
@@ -171,15 +171,18 @@
 {
 	int ret=NOTIFY_DONE;
 	struct notifier_block *nb = *n;
+	struct notifier_block *next;
 
 	while(nb)
 	{
-		ret=nb->notifier_call(nb,val,v);
+		/* Determining next here allows the notifier to unregister itself */
+		next = nb->next;
+		ret = nb->notifier_call(nb,val,v);
 		if(ret&NOTIFY_STOP_MASK)
 		{
 			return ret;
 		}
-		nb=nb->next;
+		nb = next;
 	}
 	return ret;
 }
-
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