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>

1 files changed, 10 insertions, 38 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index c5cf15e1eb57..1874c7418319 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -702,7 +702,7 @@ struct rq {
 #endif
 
 #ifdef CONFIG_SMP
-        struct task_struct *wake_list;
+        struct llist_head wake_list;
 #endif
 };
 
@@ -2698,42 +2698,26 @@ static int ttwu_remote(struct task_struct *p, int wake_flags)
 }
 
 #ifdef CONFIG_SMP
-static void sched_ttwu_do_pending(struct task_struct *list)
+static void sched_ttwu_pending(void)
 {
         struct rq *rq = this_rq();
+        struct llist_node *llist = llist_del_all(&rq->wake_list);
+        struct task_struct *p;
 
         raw_spin_lock(&rq->lock);
 
-        while (list) {
-                struct task_struct *p = list;
-                list = list->wake_entry;
+        while (llist) {
+                p = llist_entry(llist, struct task_struct, wake_entry);
+                llist = llist_next(llist);
                 ttwu_do_activate(rq, p, 0);
         }
 
         raw_spin_unlock(&rq->lock);
 }
 
-#ifdef CONFIG_HOTPLUG_CPU
-
-static void sched_ttwu_pending(void)
-{
-        struct rq *rq = this_rq();
-        struct task_struct *list = xchg(&rq->wake_list, NULL);
-
-        if (!list)
-                return;
-
-        sched_ttwu_do_pending(list);
-}
-
-#endif /* CONFIG_HOTPLUG_CPU */
-
 void scheduler_ipi(void)
 {
-        struct rq *rq = this_rq();
-        struct task_struct *list = xchg(&rq->wake_list, NULL);
-
-        if (!list)
+        if (llist_empty(&this_rq()->wake_list))
                 return;
 
         /*
@@ -2750,25 +2734,13 @@ void scheduler_ipi(void)
          * somewhat pessimize the simple resched case.
          */
         irq_enter();
-        sched_ttwu_do_pending(list);
+        sched_ttwu_pending();
         irq_exit();
 }
 
 static void ttwu_queue_remote(struct task_struct *p, int cpu)
 {
-        struct rq *rq = cpu_rq(cpu);
-        struct task_struct *next = rq->wake_list;
-
-        for (;;) {
-                struct task_struct *old = next;
-
-                p->wake_entry = next;
-                next = cmpxchg(&rq->wake_list, old, p);
-                if (next == old)
-                        break;
-        }
-
-        if (!next)
+        if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list))
                 smp_send_reschedule(cpu);
 }