[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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