sched: Convert to struct llist

Use the generic llist primitives.

We had a private lockless list implementation in the scheduler in the wake-list
code, now that we have a generic llist implementation that provides all required
operations, switch to it.

This patch is not expected to change any behavior.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1315836353.26517.42.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/sched.h

@@ -90,6 +90,7 @@ struct sched_param {
 #include <linux/task_io_accounting.h>
 #include <linux/latencytop.h>
 #include <linux/cred.h>
+#include <linux/llist.h>
 
 #include <asm/processor.h>
 
@@ -1225,7 +1226,7 @@ struct task_struct {
 	unsigned int ptrace;
 
 #ifdef CONFIG_SMP
-	struct task_struct *wake_entry;
+	struct llist_node wake_entry;
 	int on_cpu;
 #endif
 	int on_rq;