Task Services
[Driver Development API]

Collaboration diagram for Task Services:

Task Priority Range
Maximum and minimum task priorities
#define	RTDM_TASK_LOWEST_PRIORITY   XNCORE_LOW_PRIO
#define	RTDM_TASK_HIGHEST_PRIORITY   XNCORE_HIGH_PRIO
Task Priority Modification
Raise or lower task priorities by one level
#define	RTDM_TASK_RAISE_PRIORITY   (+1)
#define	RTDM_TASK_LOWER_PRIORITY   (-1)
Typedefs
typedef void(*	rtdm_task_proc_t )(void *arg)
	Real-time task procedure.
Functions
int	rtdm_task_init (rtdm_task_t *task, const char *name, rtdm_task_proc_t task_proc, void *arg, int priority, nanosecs_rel_t period)
void	rtdm_task_destroy (rtdm_task_t *task)
void	rtdm_task_set_priority (rtdm_task_t *task, int priority)
int	rtdm_task_set_period (rtdm_task_t *task, nanosecs_rel_t period)
int	rtdm_task_wait_period (void)
int	rtdm_task_unblock (rtdm_task_t *task)
rtdm_task_t *	rtdm_task_current (void)
int	rtdm_task_sleep (nanosecs_rel_t delay)
int	rtdm_task_sleep_until (nanosecs_abs_t wakeup_time)
int	rtdm_task_sleep_abs (nanosecs_abs_t wakeup_time, enum rtdm_timer_mode mode)
void	rtdm_task_join_nrt (rtdm_task_t *task, unsigned int poll_delay)
void	rtdm_task_busy_sleep (nanosecs_rel_t delay)

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Typedef Documentation

typedef void(* rtdm_task_proc_t)(void *arg)

Real-time task procedure.

Parameters:

[in,out]

arg

argument as passed to rtdm_task_init()

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Function Documentation

void rtdm_task_busy_sleep

(

nanosecs_rel_t

delay

)

Busy-wait a specified amount of time

Parameters:

[in]

delay

Delay in nanoseconds. Note that a zero delay does not have the meaning of RTDM_TIMEOUT_INFINITE here.

Note:

The caller must not be migratable to different CPUs while executing this service. Otherwise, the actual delay will be undefined.

Environments:

This service can be called from:

• Kernel module initialization/cleanup code
• Interrupt service routine (should be avoided or kept short)
• Kernel-based task
• User-space task (RT, non-RT)

Rescheduling: never (except due to external interruptions).

rtdm_task_t* rtdm_task_current

(

void

)

Get current real-time task

Returns:

Pointer to task handle Environments: This service can be called from: - Kernel-based task

• User-space task (RT, non-RT) Rescheduling: never.

void rtdm_task_destroy

(

rtdm_task_t *

task

)

Destroy a real-time task

Parameters:

[in,out]

task

Task handle as returned by rtdm_task_init()

Note:

Passing the same task handle to RTDM services after the completion of this function is not allowed.

Environments:

This service can be called from:

• Kernel module initialization/cleanup code
• Kernel-based task
• User-space task (RT, non-RT)

Rescheduling: never.

int rtdm_task_init	(	rtdm_task_t *	task,
		const char *	name,
		rtdm_task_proc_t	task_proc,
		void *	arg,
		int	priority,
		nanosecs_rel_t	period
	)

Intialise and start a real-time task After initialising a task, the task handle remains valid and can be passed to RTDM services until either rtdm_task_destroy() or rtdm_task_join_nrt() was invoked.

Parameters:

[in,out]	task	Task handle
[in]	name	Optional task name
[in]	task_proc	Procedure to be executed by the task
[in]	arg	Custom argument passed to task_proc() on entry
[in]	priority	Priority of the task, see also Task Priority Range
[in]	period	Period in nanoseconds of a cyclic task, 0 for non-cyclic mode

Returns:

0 on success, otherwise negative error code

Environments:

This service can be called from:

• Kernel module initialization/cleanup code
• Kernel-based task
• User-space task (RT, non-RT)

Rescheduling: possible.

void rtdm_task_join_nrt	(	rtdm_task_t *	task,
		unsigned int	poll_delay
	)

Wait on a real-time task to terminate

Parameters:

[in,out]	task	Task handle as returned by rtdm_task_init()
[in]	poll_delay	Delay in milliseconds between periodic tests for the state of the real-time task. This parameter is ignored if the termination is internally realised without polling.

Note:

Passing the same task handle to RTDM services after the completion of this function is not allowed.

This service does not trigger the termination of the targeted task. The user has to take of this, otherwise rtdm_task_join_nrt() will never return.

Environments:

This service can be called from:

• Kernel module initialization/cleanup code
• User-space task (non-RT)

Rescheduling: possible.

int rtdm_task_set_period	(	rtdm_task_t *	task,
		nanosecs_rel_t	period
	)

Adjust real-time task period

Parameters:

[in,out]	task	Task handle as returned by rtdm_task_init()
[in]	period	New period in nanoseconds of a cyclic task, 0 for non-cyclic mode Environments: This service can be called from: - Kernel module initialization/cleanup code Interrupt service routine Kernel-based task User-space task (RT, non-RT) Rescheduling: possible.

void rtdm_task_set_priority	(	rtdm_task_t *	task,
		int	priority
	)

Adjust real-time task priority

Parameters:

[in,out]	task	Task handle as returned by rtdm_task_init()
[in]	priority	New priority of the task, see also Task Priority Range Environments: This service can be called from: - Kernel module initialization/cleanup code Interrupt service routine Kernel-based task User-space task (RT, non-RT) Rescheduling: possible.

int rtdm_task_sleep

(

nanosecs_rel_t

delay

)

Sleep a specified amount of time

Parameters:

[in]

delay

Delay in nanoseconds, see RTDM_TIMEOUT_xxx for special values.

Returns:

0 on success, otherwise:

• -EINTR is returned if calling task has been unblock by a signal or explicitly via rtdm_task_unblock().

• -EPERM may be returned if an illegal invocation environment is detected.

Environments:

This service can be called from:

• Kernel-based task
• User-space task (RT)

Rescheduling: always.

int rtdm_task_sleep_abs	(	nanosecs_abs_t	wakeup_time,
		enum rtdm_timer_mode	mode
	)

Sleep until a specified absolute time

Parameters:

[in]	wakeup_time	Absolute timeout in nanoseconds
[in]	mode	Selects the timer mode, see RTDM_TIMERMODE_xxx for details

Returns:

0 on success, otherwise: - -EINTR is returned if calling task has been unblock by a signal or explicitly via rtdm_task_unblock().

• -EPERM may be returned if an illegal invocation environment is detected.

• -EINVAL is returned if an invalid parameter was passed.

Environments:

This service can be called from:

• Kernel-based task
• User-space task (RT)

Rescheduling: always, unless the specified time already passed.

int rtdm_task_sleep_until

(

nanosecs_abs_t

wakeup_time

)

Sleep until a specified absolute time

Deprecated:

Use rtdm_task_sleep_abs instead!

Parameters:

[in]

wakeup_time

Absolute timeout in nanoseconds

Returns:

0 on success, otherwise:

• -EINTR is returned if calling task has been unblock by a signal or explicitly via rtdm_task_unblock().

• -EPERM may be returned if an illegal invocation environment is detected.

Environments:

This service can be called from:

• Kernel-based task
• User-space task (RT)

Rescheduling: always, unless the specified time already passed.

int rtdm_task_unblock

(

rtdm_task_t *

task

)

Activate a blocked real-time task

Returns:

Non-zero is returned if the task was actually unblocked from a pending wait state, 0 otherwise.

Environments:

This service can be called from:

• Kernel module initialization/cleanup code
• Interrupt service routine
• Kernel-based task
• User-space task (RT, non-RT)

Rescheduling: possible.

int rtdm_task_wait_period

(

void

)

Wait on next real-time task period

Returns:

0 on success, otherwise: - -EINVAL is returned if calling task is not in periodic mode.

• -ETIMEDOUT is returned if a timer overrun occurred, which indicates that a previous release point has been missed by the calling task.

Environments:

This service can be called from:

• Kernel-based task
• User-space task (RT)

Rescheduling: always, unless a timer overrun occured.

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