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[src/trunk]: src/sys/external/bsd/common/linux Fix semantics of flush_work an...
details: https://anonhg.NetBSD.org/src/rev/ad1376000d71
branches: trunk
changeset: 993057:ad1376000d71
user: riastradh <riastradh%NetBSD.org@localhost>
date: Mon Aug 27 15:03:20 2018 +0000
description:
Fix semantics of flush_work and flush_delayed_work.
- Change return type to void.
=> Upstream it is bool, but exactly one of hundreds of callers
actually use it, and I don't think the semantics is clear.
- Make sure to wait for whichever of the current work _and_ the next
batch queued is currently there in the workqueue.
- Don't retry a cancelled callout. Cancellation in the state
DELAYED_WORK_CANCELLED is guaranteed.
diffstat:
sys/external/bsd/common/include/linux/workqueue.h | 6 +-
sys/external/bsd/common/linux/linux_work.c | 96 +++++++++++++++-------
2 files changed, 66 insertions(+), 36 deletions(-)
diffs (179 lines):
diff -r 04d65e4ea153 -r ad1376000d71 sys/external/bsd/common/include/linux/workqueue.h
--- a/sys/external/bsd/common/include/linux/workqueue.h Mon Aug 27 15:03:07 2018 +0000
+++ b/sys/external/bsd/common/include/linux/workqueue.h Mon Aug 27 15:03:20 2018 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: workqueue.h,v 1.10 2018/08/27 14:58:40 riastradh Exp $ */
+/* $NetBSD: workqueue.h,v 1.11 2018/08/27 15:03:20 riastradh Exp $ */
/*-
* Copyright (c) 2013, 2018 The NetBSD Foundation, Inc.
@@ -107,7 +107,7 @@
bool queue_work(struct workqueue_struct *, struct work_struct *);
bool cancel_work(struct work_struct *);
bool cancel_work_sync(struct work_struct *);
-bool flush_work(struct work_struct *);
+void flush_work(struct work_struct *);
void INIT_DELAYED_WORK(struct delayed_work *,
void (*)(struct work_struct *));
@@ -118,7 +118,7 @@
unsigned long ticks);
bool cancel_delayed_work(struct delayed_work *);
bool cancel_delayed_work_sync(struct delayed_work *);
-bool flush_delayed_work(struct delayed_work *);
+void flush_delayed_work(struct delayed_work *);
struct work_struct *
current_work(void);
diff -r 04d65e4ea153 -r ad1376000d71 sys/external/bsd/common/linux/linux_work.c
--- a/sys/external/bsd/common/linux/linux_work.c Mon Aug 27 15:03:07 2018 +0000
+++ b/sys/external/bsd/common/linux/linux_work.c Mon Aug 27 15:03:20 2018 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: linux_work.c,v 1.27 2018/08/27 15:03:07 riastradh Exp $ */
+/* $NetBSD: linux_work.c,v 1.28 2018/08/27 15:03:20 riastradh Exp $ */
/*-
* Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_work.c,v 1.27 2018/08/27 15:03:07 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_work.c,v 1.28 2018/08/27 15:03:20 riastradh Exp $");
#include <sys/types.h>
#include <sys/atomic.h>
@@ -754,72 +754,102 @@
flush_workqueue(system_wq);
}
-void
-flush_workqueue(struct workqueue_struct *wq)
+static void
+flush_workqueue_locked(struct workqueue_struct *wq)
{
uint64_t gen;
+ KASSERT(mutex_owned(&wq->wq_lock));
+
+ /* Get the current generation number. */
+ gen = wq->wq_gen;
+
+ /*
+ * If there's a batch of work in progress, we must wait for the
+ * worker thread to finish that batch.
+ */
+ if (wq->wq_current_work != NULL)
+ gen++;
+
+ /*
+ * If there's any work yet to be claimed from the queue by the
+ * worker thread, we must wait for it to finish one more batch
+ * too.
+ */
+ if (!TAILQ_EMPTY(&wq->wq_queue))
+ gen++;
+
+ /* Wait until the generation number has caught up. */
+ while (wq->wq_gen < gen)
+ cv_wait(&wq->wq_cv, &wq->wq_lock);
+}
+
+void
+flush_workqueue(struct workqueue_struct *wq)
+{
+
mutex_enter(&wq->wq_lock);
- if (wq->wq_current_work || !TAILQ_EMPTY(&wq->wq_queue)) {
- gen = wq->wq_gen;
- do {
- cv_wait(&wq->wq_cv, &wq->wq_lock);
- } while (gen == wq->wq_gen);
- }
+ flush_workqueue_locked(wq);
mutex_exit(&wq->wq_lock);
}
-bool
+void
flush_work(struct work_struct *work)
{
struct workqueue_struct *wq;
/* If there's no workqueue, nothing to flush. */
if ((wq = work->work_queue) == NULL)
- return false;
+ return;
flush_workqueue(wq);
- return true;
}
-bool
+void
flush_delayed_work(struct delayed_work *dw)
{
struct workqueue_struct *wq;
- bool do_flush = false;
/* If there's no workqueue, nothing to flush. */
if ((wq = dw->work.work_queue) == NULL)
- return false;
+ return;
mutex_enter(&wq->wq_lock);
- if (__predict_false(dw->work.work_queue != wq)) {
- do_flush = true;
- } else {
-retry: switch (dw->dw_state) {
+ if (__predict_true(dw->work.work_queue == wq)) {
+ switch (dw->dw_state) {
case DELAYED_WORK_IDLE:
- if (wq->wq_current_work != &dw->work) {
- TAILQ_REMOVE(&wq->wq_queue, &dw->work,
- work_entry);
- } else {
- do_flush = true;
- }
+ /*
+ * It has a workqueue assigned and the callout
+ * is idle, so it must be in progress or on the
+ * queue. In that case, wait for it to
+ * complete. Waiting for the whole queue to
+ * flush is overkill, but doesn't hurt.
+ */
+ flush_workqueue_locked(wq);
break;
case DELAYED_WORK_SCHEDULED:
case DELAYED_WORK_RESCHEDULED:
case DELAYED_WORK_CANCELLED:
+ /*
+ * The callout is still scheduled to run.
+ * Notify it that we are cancelling, and try to
+ * stop the callout before it runs.
+ *
+ * If we do stop the callout, we are now
+ * responsible for dissociating the work from
+ * the queue.
+ *
+ * Otherwise, wait for it to complete and
+ * dissociate itself -- it will not put itself
+ * on the workqueue once it is cancelled.
+ */
dw->dw_state = DELAYED_WORK_CANCELLED;
- callout_halt(&dw->dw_callout, &wq->wq_lock);
- goto retry;
+ if (!callout_halt(&dw->dw_callout, &wq->wq_lock))
+ cancel_delayed_work_done(wq, dw);
default:
panic("invalid delayed work state: %d",
dw->dw_state);
}
}
mutex_exit(&wq->wq_lock);
-
- if (do_flush)
- flush_workqueue(wq);
-
- return true;
}
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