[src/trunk]: src/sys/external/bsd/common/linux Exercise greater care in acqui...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/de18a4314a19
branches:  trunk
changeset: 835428:de18a4314a19
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Mon Aug 27 14:59:20 2018 +0000

description:
Exercise greater care in acquiring and releasing work.

diffstat:

 sys/external/bsd/common/linux/linux_work.c |  47 ++++++++++++++++++++++++-----
 1 files changed, 39 insertions(+), 8 deletions(-)

diffs (110 lines):

diff -r 923ec2f69b62 -r de18a4314a19 sys/external/bsd/common/linux/linux_work.c
--- a/sys/external/bsd/common/linux/linux_work.c        Mon Aug 27 14:59:04 2018 +0000
+++ b/sys/external/bsd/common/linux/linux_work.c        Mon Aug 27 14:59:20 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: linux_work.c,v 1.16 2018/08/27 14:58:57 riastradh Exp $        */
+/*     $NetBSD: linux_work.c,v 1.17 2018/08/27 14:59:20 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 1.16 2018/08/27 14:58:57 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_work.c,v 1.17 2018/08/27 14:59:20 riastradh Exp $");
 
 #include <sys/types.h>
 #include <sys/atomic.h>
@@ -60,6 +60,11 @@
 
 static void __dead     linux_workqueue_thread(void *);
 static void            linux_workqueue_timeout(void *);
+static struct workqueue_struct *
+                       acquire_work(struct work_struct *,
+                           struct workqueue_struct *);
+static void            release_work(struct work_struct *,
+                           struct workqueue_struct *);
 static void            queue_delayed_work_anew(struct workqueue_struct *,
                            struct delayed_work *, unsigned long);
 
@@ -238,7 +243,7 @@
                        if (wq->wq_requeued)
                                wq->wq_requeued = false;
                        else
-                               work->work_queue = NULL;
+                               release_work(work, wq);
                        wq->wq_current_work = NULL;
                        cv_broadcast(&wq->wq_cv);
                }
@@ -278,6 +283,7 @@
                dw->dw_state = DELAYED_WORK_IDLE;
                callout_destroy(&dw->dw_callout);
                TAILQ_REMOVE(&wq->wq_delayed, dw, dw_entry);
+               release_work(&dw->work, wq);
                break;
        default:
                panic("delayed work callout in bad state: %p", dw);
@@ -316,6 +322,33 @@
        work->func = fn;
 }
 
+static struct workqueue_struct *
+acquire_work(struct work_struct *work, struct workqueue_struct *wq)
+{
+       struct workqueue_struct *wq0;
+
+       KASSERT(mutex_owned(&wq->wq_lock));
+
+       wq0 = atomic_cas_ptr(&work->work_queue, NULL, wq);
+       if (wq0 == NULL) {
+               membar_enter();
+               KASSERT(work->work_queue == wq);
+       }
+
+       return wq0;
+}
+
+static void
+release_work(struct work_struct *work, struct workqueue_struct *wq)
+{
+
+       KASSERT(work->work_queue == wq);
+       KASSERT(mutex_owned(&wq->wq_lock));
+
+       membar_exit();
+       work->work_queue = NULL;
+}
+
 bool
 schedule_work(struct work_struct *work)
 {
@@ -332,8 +365,7 @@
        KASSERT(wq != NULL);
 
        mutex_enter(&wq->wq_lock);
-       if (__predict_true((wq0 = atomic_cas_ptr(&work->work_queue, NULL, wq))
-               == NULL)) {
+       if (__predict_true((wq0 = acquire_work(work, wq)) == NULL)) {
                TAILQ_INSERT_TAIL(&wq->wq_queue, work, work_entry);
                newly_queued = true;
        } else {
@@ -462,8 +494,7 @@
        bool newly_queued;
 
        mutex_enter(&wq->wq_lock);
-       if (__predict_true((wq0 = atomic_cas_ptr(&dw->work.work_queue, NULL,
-                       wq)) == NULL)) {
+       if (__predict_true((wq0 = acquire_work(&dw->work, wq)) == NULL)) {
                KASSERT(dw->dw_state == DELAYED_WORK_IDLE);
                queue_delayed_work_anew(wq, dw, ticks);
                newly_queued = true;
@@ -484,7 +515,7 @@
        bool timer_modified;
 
        mutex_enter(&wq->wq_lock);
-       if ((wq0 = atomic_cas_ptr(&dw->work.work_queue, NULL, wq)) == NULL) {
+       if ((wq0 = acquire_work(&dw->work, wq)) == NULL) {
                KASSERT(dw->dw_state == DELAYED_WORK_IDLE);
                queue_delayed_work_anew(wq, dw, ticks);
                timer_modified = false;