svn commit: r262064 - in stable/9: share/man/man9 sys/kern sys/sys

Andriy Gapon avg at FreeBSD.org
Mon Feb 17 15:29:48 UTC 2014


Author: avg
Date: Mon Feb 17 15:29:46 2014
New Revision: 262064
URL: http://svnweb.freebsd.org/changeset/base/262064

Log:
  MFC r258713,262062: add taskqueue_drain_all

Modified:
  stable/9/share/man/man9/Makefile
  stable/9/share/man/man9/taskqueue.9
  stable/9/sys/kern/subr_taskqueue.c
  stable/9/sys/sys/taskqueue.h
Directory Properties:
  stable/9/share/man/man9/   (props changed)
  stable/9/sys/   (props changed)
  stable/9/sys/sys/   (props changed)

Modified: stable/9/share/man/man9/Makefile
==============================================================================
--- stable/9/share/man/man9/Makefile	Mon Feb 17 15:24:49 2014	(r262063)
+++ stable/9/share/man/man9/Makefile	Mon Feb 17 15:29:46 2014	(r262064)
@@ -1308,6 +1308,7 @@ MLINKS+=sysctl_ctx_init.9 sysctl_ctx_ent
 MLINKS+=SYSINIT.9 SYSUNINIT.9
 MLINKS+=taskqueue.9 TASK_INIT.9 \
 	taskqueue.9 TASK_INITIALIZER.9 \
+	taskqueue.9 taskqueue_block.9 \
 	taskqueue.9 taskqueue_cancel.9 \
 	taskqueue.9 taskqueue_create.9 \
 	taskqueue.9 taskqueue_create_fast.9 \
@@ -1315,13 +1316,15 @@ MLINKS+=taskqueue.9 TASK_INIT.9 \
 	taskqueue.9 TASKQUEUE_DEFINE.9 \
 	taskqueue.9 TASKQUEUE_DEFINE_THREAD.9 \
 	taskqueue.9 taskqueue_drain.9 \
+	taskqueue.9 taskqueue_drain_all.9 \
 	taskqueue.9 taskqueue_enqueue.9 \
 	taskqueue.9 taskqueue_enqueue_fast.9 \
 	taskqueue.9 TASKQUEUE_FAST_DEFINE.9 \
 	taskqueue.9 TASKQUEUE_FAST_DEFINE_THREAD.9 \
 	taskqueue.9 taskqueue_free.9 \
 	taskqueue.9 taskqueue_member.9 \
-	taskqueue.9 taskqueue_run.9
+	taskqueue.9 taskqueue_run.9 \
+	taskqueue.9 taskqueue_unblock.9
 MLINKS+=time.9 boottime.9 \
 	time.9 time_second.9 \
 	time.9 time_uptime.9

Modified: stable/9/share/man/man9/taskqueue.9
==============================================================================
--- stable/9/share/man/man9/taskqueue.9	Mon Feb 17 15:24:49 2014	(r262063)
+++ stable/9/share/man/man9/taskqueue.9	Mon Feb 17 15:29:46 2014	(r262064)
@@ -28,7 +28,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 4, 2012
+.Dd January 24, 2014
 .Dt TASKQUEUE 9
 .Os
 .Sh NAME
@@ -75,6 +75,12 @@ struct timeout_task;
 .Fn taskqueue_drain "struct taskqueue *queue" "struct task *task"
 .Ft void
 .Fn taskqueue_drain_timeout "struct taskqueue *queue" "struct timeout_task *timeout_task"
+.Ft void
+.Fn taskqueue_drain_all "struct taskqueue *queue"
+.Ft void
+.Fn taskqueue_block "struct taskqueue *queue"
+.Ft void
+.Fn taskqueue_unblock "struct taskqueue *queue"
 .Ft int
 .Fn taskqueue_member "struct taskqueue *queue" "struct thread *td"
 .Ft void
@@ -227,6 +233,73 @@ function is used to wait for the schedul
 There is no guarantee that the task will not be
 enqueued after call to
 .Fn taskqueue_drain .
+If the caller wants to put the task into a known state,
+then before calling
+.Fn taskqueue_drain
+the caller should use out-of-band means to ensure that the task
+would not be enqueued.
+For example, if the task is enqueued by an interrupt filter, then
+the interrupt could be disabled.
+.Pp
+The
+.Fn taskqueue_drain_all
+function is used to wait for all pending and running tasks that
+are enqueued on the taskqueue to finish.
+The caller must arrange that the tasks are not re-enqueued.
+Note that
+.Fn taskqueue_drain_all
+currently does not handle tasks with delayed enqueueing.
+.Pp
+The
+.Fn taskqueue_block
+function blocks the taskqueue.
+It prevents any enqueued but not running tasks from being executed.
+Future calls to
+.Fn taskqueue_enqueue
+will enqueue tasks, but the tasks will not be run until
+.Fn taskqueue_unblock
+is called.
+Please note that
+.Fn taskqueue_block
+does not wait for any currently running tasks to finish.
+Thus, the
+.Fn taskqueue_block
+does not provide a guarantee that
+.Fn taskqueue_run
+is not running after
+.Fn taskqueue_block
+returns, but it does provide a guarantee that
+.Fn taskqueue_run
+will not be called again
+until
+.Fn taskqueue_unblock
+is called.
+If the caller requires a guarantee that
+.Fn taskqueue_run
+is not running, then this must be arranged by the caller.
+Note that if
+.Fn taskqueue_drain
+is called on a task that is enqueued on a taskqueue that is blocked by
+.Fn taskqueue_block ,
+then
+.Fn taskqueue_drain
+can not return until the taskqueue is unblocked.
+This can result in a deadlock if the thread blocked in
+.Fn taskqueue_drain
+is the thread that is supposed to call
+.Fn taskqueue_unblock .
+Thus, use of
+.Fn taskqueue_drain
+after
+.Fn taskqueue_block
+is discouraged, because the state of the task can not be known in advance.
+The same caveat applies to
+.Fn taskqueue_drain_all .
+.Pp
+The
+.Fn taskqueue_unblock
+function unblocks the previously blocked taskqueue.
+All enqueued tasks can be run after this call.
 .Pp
 The
 .Fn taskqueue_member

Modified: stable/9/sys/kern/subr_taskqueue.c
==============================================================================
--- stable/9/sys/kern/subr_taskqueue.c	Mon Feb 17 15:24:49 2014	(r262063)
+++ stable/9/sys/kern/subr_taskqueue.c	Mon Feb 17 15:29:46 2014	(r262064)
@@ -264,6 +264,15 @@ taskqueue_enqueue_timeout(struct taskque
 	return (res);
 }
 
+static void
+taskqueue_drain_running(struct taskqueue *queue)
+{
+
+	while (!TAILQ_EMPTY(&queue->tq_active))
+		TQ_SLEEP(queue, &queue->tq_active, &queue->tq_mutex,
+		    PWAIT, "-", 0);
+}
+
 void
 taskqueue_block(struct taskqueue *queue)
 {
@@ -316,6 +325,8 @@ taskqueue_run_locked(struct taskqueue *q
 		wakeup(task);
 	}
 	TAILQ_REMOVE(&queue->tq_active, &tb, tb_link);
+	if (TAILQ_EMPTY(&queue->tq_active))
+		wakeup(&queue->tq_active);
 }
 
 void
@@ -400,6 +411,25 @@ taskqueue_drain(struct taskqueue *queue,
 }
 
 void
+taskqueue_drain_all(struct taskqueue *queue)
+{
+	struct task *task;
+
+	if (!queue->tq_spin)
+		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, __func__);
+
+	TQ_LOCK(queue);
+	task = STAILQ_LAST(&queue->tq_queue, task, ta_link);
+	if (task != NULL)
+		while (task->ta_pending != 0)
+			TQ_SLEEP(queue, task, &queue->tq_mutex, PWAIT, "-", 0);
+	taskqueue_drain_running(queue);
+	KASSERT(STAILQ_EMPTY(&queue->tq_queue),
+	    ("taskqueue queue is not empty after draining"));
+	TQ_UNLOCK(queue);
+}
+
+void
 taskqueue_drain_timeout(struct taskqueue *queue,
     struct timeout_task *timeout_task)
 {

Modified: stable/9/sys/sys/taskqueue.h
==============================================================================
--- stable/9/sys/sys/taskqueue.h	Mon Feb 17 15:24:49 2014	(r262063)
+++ stable/9/sys/sys/taskqueue.h	Mon Feb 17 15:29:46 2014	(r262064)
@@ -71,6 +71,7 @@ int	taskqueue_cancel_timeout(struct task
 void	taskqueue_drain(struct taskqueue *queue, struct task *task);
 void	taskqueue_drain_timeout(struct taskqueue *queue,
 	    struct timeout_task *timeout_task);
+void	taskqueue_drain_all(struct taskqueue *queue);
 void	taskqueue_free(struct taskqueue *queue);
 void	taskqueue_run(struct taskqueue *queue);
 void	taskqueue_block(struct taskqueue *queue);


More information about the svn-src-stable-9 mailing list