Task Services
[Driver Development API]

Collaboration diagram for Task Services:


Task Priority Range

Maximum and minimum task priorities

#define RTDM_TASK_LOWEST_PRIORITY   XNSCHED_LOW_PRIO
#define RTDM_TASK_HIGHEST_PRIORITY   XNSCHED_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)
 Intialise and start a real-time task.
void rtdm_task_destroy (rtdm_task_t *task)
 Destroy a real-time task.
void rtdm_task_set_priority (rtdm_task_t *task, int priority)
 Adjust real-time task priority.
int rtdm_task_set_period (rtdm_task_t *task, nanosecs_rel_t period)
 Adjust real-time task period.
int rtdm_task_wait_period (void)
 Wait on next real-time task period.
int rtdm_task_unblock (rtdm_task_t *task)
 Activate a blocked real-time task.
rtdm_task_t * rtdm_task_current (void)
 Get current real-time task.
int rtdm_task_sleep (nanosecs_rel_t delay)
 Sleep a specified amount of time.
int rtdm_task_sleep_until (nanosecs_abs_t wakeup_time)
 Sleep until a specified absolute time.
int rtdm_task_sleep_abs (nanosecs_abs_t wakeup_time, enum rtdm_timer_mode mode)
 Sleep until a specified absolute time.
void rtdm_task_join_nrt (rtdm_task_t *task, unsigned int poll_delay)
 Wait on a real-time task to terminate.
void rtdm_task_busy_sleep (nanosecs_rel_t delay)
 Busy-wait a specified amount of time.

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()

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.

References xnpod_delete_thread(), xnpod_init_thread(), xnpod_set_thread_periodic(), and xnpod_start_thread().

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.

References XNZOMBIE.

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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