Author: mdf
Date: Mon Nov 8 20:56:31 2010
New Revision: 215011
URL: http://svn.freebsd.org/changeset/base/215011
Log:
Add a taskqueue_cancel(9) to cancel a pending task without waiting for
it to run as taskqueue_drain(9) does.
Requested by: hselasky
Original code: jeff
Reviewed by: jhb
MFC after: 2 weeks
Modified:
head/share/man/man9/Makefile
head/share/man/man9/taskqueue.9
head/sys/kern/subr_taskqueue.c
head/sys/sys/taskqueue.h
Modified: head/share/man/man9/Makefile
==============================================================================
--- head/share/man/man9/Makefile Mon Nov 8 20:44:11 2010
(r215010)
+++ head/share/man/man9/Makefile Mon Nov 8 20:56:31 2010
(r215011)
@@ -1212,6 +1212,7 @@ MLINKS+=sysctl_ctx_init.9 sysctl_ctx_ent
sysctl_ctx_init.9 sysctl_ctx_entry_find.9 \
sysctl_ctx_init.9 sysctl_ctx_free.9
MLINKS+=taskqueue.9 TASK_INIT.9 \
+ taskqueue.9 taskqueue_cancel.9 \
taskqueue.9 taskqueue_create.9 \
taskqueue.9 taskqueue_create_fast.9 \
taskqueue.9 TASKQUEUE_DECLARE.9 \
Modified: head/share/man/man9/taskqueue.9
==============================================================================
--- head/share/man/man9/taskqueue.9 Mon Nov 8 20:44:11 2010
(r215010)
+++ head/share/man/man9/taskqueue.9 Mon Nov 8 20:56:31 2010
(r215011)
@@ -63,6 +63,8 @@ struct task {
.Fn taskqueue_enqueue "struct taskqueue *queue" "struct task *task"
.Ft int
.Fn taskqueue_enqueue_fast "struct taskqueue *queue" "struct task *task"
+.Ft int
+.Fn taskqueue_cancel "struct taskqueue *queue" "struct task *task" "u_int
*pendp"
.Ft void
.Fn taskqueue_drain "struct taskqueue *queue" "struct task *task"
.Ft int
@@ -162,6 +164,31 @@ is called on the task pointer passed to
.Fn taskqueue_enqueue .
.Pp
The
+.Fn taskqueue_cancel
+function is used to cancel a task.
+The
+.Va ta_pending
+count is cleared, and the old value returned in the reference
+parameter
+.Fa pendp ,
+if it is non- Dv NULL .
+If the task is currently running,
+.Dv EBUSY
+is returned, otherwise 0.
+To implement a blocking
+.Fn taskqueue_cancel
+that waits for a running task to finish, it could look like:
+.Bd -literal -offset indent
+while (taskqueue_cancel(tq, task, NULL) != 0)
+ taskqueue_drain(tq, task);
+.Ed
+.Pp
+Note that, as with
+.Fn taskqueue_drain ,
+the caller is responsible for ensuring that the task is not re-enqueued
+after being canceled.
+.Pp
+The
.Fn taskqueue_drain
function is used to wait for the task to finish.
There is no guarantee that the task will not be
Modified: head/sys/kern/subr_taskqueue.c
==============================================================================
--- head/sys/kern/subr_taskqueue.c Mon Nov 8 20:44:11 2010
(r215010)
+++ head/sys/kern/subr_taskqueue.c Mon Nov 8 20:56:31 2010
(r215011)
@@ -275,6 +275,24 @@ task_is_running(struct taskqueue *queue,
return (0);
}
+int
+taskqueue_cancel(struct taskqueue *queue, struct task *task, u_int *pendp)
+{
+ u_int pending;
+ int error;
+
+ TQ_LOCK(queue);
+ if ((pending = task->ta_pending) > 0)
+ STAILQ_REMOVE(&queue->tq_queue, task, task, ta_link);
+ task->ta_pending = 0;
+ error = task_is_running(queue, task) ? EBUSY : 0;
+ TQ_UNLOCK(queue);
+
+ if (pendp != NULL)
+ *pendp = pending;
+ return (error);
+}
+
void
taskqueue_drain(struct taskqueue *queue, struct task *task)
{
Modified: head/sys/sys/taskqueue.h
==============================================================================
--- head/sys/sys/taskqueue.h Mon Nov 8 20:44:11 2010 (r215010)
+++ head/sys/sys/taskqueue.h Mon Nov 8 20:56:31 2010 (r215011)
@@ -54,6 +54,8 @@ struct taskqueue *taskqueue_create(const
int taskqueue_start_threads(struct taskqueue **tqp, int count, int pri,
const char *name, ...) __printflike(4, 5);
int taskqueue_enqueue(struct taskqueue *queue, struct task *task);
+int taskqueue_cancel(struct taskqueue *queue, struct task *task,
+ u_int *pendp);
void taskqueue_drain(struct taskqueue *queue, struct task *task);
void taskqueue_free(struct taskqueue *queue);
void taskqueue_run(struct taskqueue *queue);
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