[RFC/PATCH 4/3] rt: PI-workqueue: fixup the barrier prio

[Peter Zijlstra]

small fix to the PI stuff,
we lost the prio of the barrier waiter.
---

Index: linux-2.6/kernel/workqueue.c
===================================================================
--- linux-2.6.orig/kernel/workqueue.c
+++ linux-2.6/kernel/workqueue.c
@@ -264,6 +264,7 @@ struct wq_full_barrier {
 	struct plist_head		worklist;
 	struct wq_full_barrier 		*prev_barrier;
 	int				prev_prio;
+	int				waiter_prio;
 	struct cpu_workqueue_struct 	*cwq;
 	struct completion		done;
 };
@@ -291,6 +292,7 @@ again:
 		prio = work->entry.prio;
 		if (unlikely(worklist != &cwq->worklist)) {
 			prio = min(prio, cwq->barrier->prev_prio);
+			prio = min(prio, cwq->barrier->waiter_prio);
 			prio = min(prio, plist_first(&cwq->worklist)->prio);
 		}
 
@@ -393,14 +395,15 @@ static void wq_full_barrier_func(struct 
 	struct wq_full_barrier *barrier =
 		container_of(work, struct wq_full_barrier, work);
 	struct cpu_workqueue_struct *cwq = barrier->cwq;
+	int prio = MAX_PRIO;
 
 	spin_lock_irq(&cwq->lock);
 	barrier->prev_barrier = cwq->barrier;
 	if (cwq->barrier) {
-		barrier->prev_prio = min(cwq->barrier->prev_prio,
-				plist_first(&cwq->barrier->worklist)->prio);
-	} else
-		barrier->prev_prio = MAX_PRIO;
+		prio = min(prio, cwq->barrier->waiter_prio);
+		prio = min(prio, plist_first(&cwq->barrier->worklist)->prio);
+	}
+	barrier->prev_prio = prio;
 	cwq->barrier = barrier;
 	spin_unlock_irq(&cwq->lock);
 }
@@ -415,6 +418,7 @@ static void insert_wq_full_barrier(struc
 	plist_head_splice(&cwq->worklist, &barr->worklist);
 	barr->cwq = cwq;
 	init_completion(&barr->done);
+	barr->waiter_prio = current->normal_prio;
 
 	insert_work(cwq, &barr->work, 0, current->normal_prio, 1);
 }

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