SYSMON_TASKQ(9) BSD Kernel Developer's Manual SYSMON_TASKQ(9)NAME
sysmon_taskq -- general purpose system monitoring task queue
sysmon_task_queue_sched(u_int pri, void (*func)(void *), void *arg);
The machine-independent sysmon_taskq provides a simple general purpose task queue. It can be used to run callbacks that require thread con-
text, but do not warrant the use of a more fine-grained solution.
Although the intended usage is related to the context of system monitoring and power management, also other comparable functions are suitable
The necessary internal data structures are initialized during system startup by sysmon_task_queue_preinit(). Before actual usage, a machine-
dependent procedure should finish the initialization by calling sysmon_task_queue_init(). This will create a kernel thread that can be later
halted by sysmon_task_queue_fini(). All scheduled tasks are executed before the queue is halted.
The sysmon_task_queue_sched() enqueues func to be executed at the priority pri. If pri is 0, the scheduled function will be placed as the
last element in the queue. The single argument passed to func is specified by arg.
Upon successful completion, sysmon_task_queue_sched() returns 0. Otherwise, the following error values are returned:
[EINVAL] An invalid parameter was specified.
[ENOMEM] There was not enough memory.
SEE ALSO queue(3), kthread(9), workqueue(9)AUTHORS
Jason R. Thorpe <thorpej@NetBSD.org>
BSD January 24, 2010 BSD
Check Out this Related Man Page
taskq(9F) Kernel Functions for Drivers taskq(9F)NAME
taskq, ddi_taskq_create, ddi_taskq_destroy, ddi_taskq_dispatch, ddi_taskq_wait, ddi_taskq_suspend, taskq_suspended, ddi_taskq_resume - Ker-
nel task queue operations
ddi_taskq_t *ddi_taskq_create(dev_info_t *dip, const char *name,
int nthreads, pri_t pri, uint_t cflags);
void ddi_taskq_destroy(ddi_taskq_t *tq);
int ddi_taskq_dispatch(ddi_taskq_t *tq, void (* func)(void *),
void *arg, uint_t dflags);
void ddi_taskq_wait(ddi_taskq_t *tq);
void ddi_taskq_suspend(ddi_taskq_t *tq);
boolean_t ddi_taskq_suspended(ddi_taskq_t *tq);
void ddi_taskq_resume(ddi_taskq_t *tq);
Solaris DDI specific (Solaris DDI)
dip Pointer to the device's dev_info structure. May be NULL for kernel modules that do not have an associated dev_info
name Descriptive string. Only alphanumeric characters can be used in name and spaces are not allowed. The name should be
nthreads Number of threads servicing the task queue. Note that the request ordering is guaranteed (tasks are processed in the order
scheduled) if the taskq is created with a single servicing thread.
pri Priority of threads servicing the task queue. Drivers and modules should specify TASKQ_DEFAULTPRI.
cflags Should pass 0 as flags.
func Callback function to call.
arg Argument to the callback function.
dflags Possible dflags are:
DDI_SLEEP Allow sleeping (blocking) until memory is available.
DDI_NOSLEEP Return DDI_FAILURE immediately if memory is not available.
tq Pointer to a task queue (ddi_taskq_t *).
tp Pointer to a thread structure.
A kernel task queue is a mechanism for general-purpose asynchronous task scheduling that enables tasks to be performed at a later time by
another thread. There are several reasons why you may utilize asynchronous task scheduling:
1. You have a task that isn't time-critical, but a current code path that is.
2. You have a task that may require grabbing locks that a thread already holds.
3. You have a task that needs to block (for example, to wait for memory), but a have a thread that cannot block in its current con-
4. You have a code path that can't complete because of a specific condition, but also can't sleep or fail. In this case, the task
is immediately queued and then is executed after the condition disappears.
5. A task queue is just a simple way to launch multiple tasks in parallel.
A task queue consists of a list of tasks, together with one or more threads to service the list. If a task queue has a single service
thread, all tasks are guaranteed to execute in the order they were dispatched. Otherwise they can be executed in any order. Note that since
tasks are placed on a list, execution of one task and should not depend on the execution of another task or a deadlock may occur. A taskq
created with a single servicing thread guarantees that all the tasks are serviced in the order in which they are scheduled.
The ddi_taskq_create() function creates a task queue instance.
The ddi_taskq_dispatch() function places taskq on the list for later execution. The dflag argument specifies whether it is allowed sleep
waiting for memory. DDI_SLEEP dispatches can sleep and are guaranteed to succeed. DDI_NOSLEEP dispatches are guaranteed not to sleep but
may fail (return DDI_FAILURE) if resources are not available.
The ddi_taskq_destroy() function waits for any scheduled tasks to complete, then destroys the taskq. The caller should guarantee that no
new tasks are scheduled for the closing taskq.
The ddi_taskq_wait() function waits for all previously scheduled tasks to complete. Note that this function does not stop any new task dis-
The ddi_taskq_suspend() function suspends all task execution until ddi_taskq_resume() is called. Although ddi_taskq_suspend() attempts to
suspend pending tasks, there are no guarantees that they will be suspended. The only guarantee is that all tasks dispatched after
ddi_taskq_suspend() will not be executed. Because it will trigger a deadlock, the ddi_taskq_suspend() function should never be called by a
task executing on a taskq.
The ddi_taskq_suspended() function returns B_TRUE if taskq is suspended, and B_FALSE otherwise. It is intended to ASSERT that the task
queue is suspended.
The ddi_taskq_resume() function resumes task queue execution.
The ddi_taskq_create() function creates an opaque handle that is used for all other taskq operations. It returns a taskq pointer on success
and NULL on failure.
The ddi_taskq_dispatch() function returns DDI_FAILURE if it can't dispatch a task and returns DDI_SUCCESS if dispatch succeeded.
The ddi_taskq_suspended() function returns B_TRUE if taskq is suspended. Otherwise B_FALSE is returned.
All functions may be called from the user or kernel contexts.
Addtionally, the ddi_taskq_dispatch function may be called from the interrupt context only if the DDI_NOSLEEP flag is set.
SunOS 5.11 1 Mar 2005 taskq(9F)