kthread_worker: reimplement flush_kthread_work() to allow freeing the work item being...

[karo-tx-linux.git] / kernel / kthread.c

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 4bfbff36d4472d83444047bbfd030c433814ef4d..b579af57ea107af579e6a155730258166dd4e176 100644 (file)
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -360,16 +360,12 @@ repeat:
                                        struct kthread_work, node);
                list_del_init(&work->node);
        }
+       worker->current_work = work;
        spin_unlock_irq(&worker->lock);
 
        if (work) {
                __set_current_state(TASK_RUNNING);
                work->func(work);
-               smp_wmb();      /* wmb worker-b0 paired with flush-b1 */
-               work->done_seq = work->queue_seq;
-               smp_mb();       /* mb worker-b1 paired with flush-b0 */
-               if (atomic_read(&work->flushing))
-                       wake_up_all(&work->done);
        } else if (!freezing(current))
                schedule();
 
@@ -386,7 +382,7 @@ static void insert_kthread_work(struct kthread_worker *worker,
        lockdep_assert_held(&worker->lock);
 
        list_add_tail(&work->node, pos);
-       work->queue_seq++;
+       work->worker = worker;
        if (likely(worker->task))
                wake_up_process(worker->task);
 }
@@ -436,25 +432,35 @@ static void kthread_flush_work_fn(struct kthread_work *work)
  */
 void flush_kthread_work(struct kthread_work *work)
 {
-       int seq = work->queue_seq;
+       struct kthread_flush_work fwork = {
+               KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
+               COMPLETION_INITIALIZER_ONSTACK(fwork.done),
+       };
+       struct kthread_worker *worker;
+       bool noop = false;
+
+retry:
+       worker = work->worker;
+       if (!worker)
+               return;
 
-       atomic_inc(&work->flushing);
+       spin_lock_irq(&worker->lock);
+       if (work->worker != worker) {
+               spin_unlock_irq(&worker->lock);
+               goto retry;
+       }
 
-       /*
-        * mb flush-b0 paired with worker-b1, to make sure either
-        * worker sees the above increment or we see done_seq update.
-        */
-       smp_mb__after_atomic_inc();
+       if (!list_empty(&work->node))
+               insert_kthread_work(worker, &fwork.work, work->node.next);
+       else if (worker->current_work == work)
+               insert_kthread_work(worker, &fwork.work, worker->work_list.next);
+       else
+               noop = true;
 
-       /* A - B <= 0 tests whether B is in front of A regardless of overflow */
-       wait_event(work->done, seq - work->done_seq <= 0);
-       atomic_dec(&work->flushing);
+       spin_unlock_irq(&worker->lock);
 
-       /*
-        * rmb flush-b1 paired with worker-b0, to make sure our caller
-        * sees every change made by work->func().
-        */
-       smp_mb__after_atomic_dec();
+       if (!noop)
+               wait_for_completion(&fwork.done);
 }
 EXPORT_SYMBOL_GPL(flush_kthread_work);