/*
* Timer Manager - rtems_timer_initiate_server directive along with
* the Timer Server Body and support routines
*
* COPYRIGHT (c) 1989-2002.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.OARcorp.com/rtems/license.html.
*
* $Id$
*/
#include <rtems/system.h>
#include <rtems/rtems/status.h>
#include <rtems/rtems/support.h>
#include <rtems/score/object.h>
#include <rtems/score/thread.h>
#include <rtems/rtems/timer.h>
#include <rtems/score/tod.h>
#include <rtems/score/watchdog.h>
#include <rtems/rtems/tasks.h>
#include <rtems/rtems/support.h>
#include <rtems/score/thread.h>
/*
* The following chains contain the list of interval timers that are
* executed in the context of the Timer Server.
*
* NOTE: These are prototyped in rtems/timer/timer.h but since we
* do not actually use them until after the Timer Server is
* initiated, we can actually declare them here and avoid forcing
* them into the minimum footprint.
*/
Chain_Control _Timer_Ticks_chain;
Chain_Control _Timer_Seconds_chain;
/*
* These variables keep track of the last time the Timer Server actually
* processed the chain.
*/
Watchdog_Interval _Timer_Server_seconds_last_time;
Watchdog_Interval _Timer_Server_ticks_last_time;
/*
* The timer used to control when the Timer Server wakes up to service
* "when" timers.
*/
Watchdog_Control _Timer_Seconds_timer;
/*PAGE
*
* _Timer_Server_body
*
* This is the server for task based timers. This task executes whenever
* a task-based timer should fire. It services both "after" and "when"
* timers. It is not created automatically but must be created explicitly
* by the application before task-based timers may be initiated.
*
* Input parameters:
* Ignored - the task argument is ignored
*
* Output parameters: NONE
*/
Thread _Timer_Server_body(
unsigned32 ignored
)
{
/*
* Initialize the "last time" markers to indicate the timer that
* the server was initiated.
*/
_Timer_Server_ticks_last_time = _Watchdog_Ticks_since_boot;
_Timer_Server_seconds_last_time = _TOD_Seconds_since_epoch;
_Thread_Disable_dispatch();
while(1) {
/*
* Block until there is something to do.
*/
_Thread_Set_state( _Timer_Server, STATES_DELAYING );
_Timer_Server_reset_ticks_timer();
_Timer_Server_reset_seconds_timer();
_Thread_Enable_dispatch();
/*
* At this point, at least one of the timers this task relies
* upon has fired. Stop them both while we process any outstanding
* timers. Before we block, we will restart them.
*/
_Timer_Server_stop_ticks_timer();
_Timer_Server_stop_seconds_timer();
/*
* Disable dispatching while processing the timers since we want
* to mimic the environment that non-task-based TSRs execute in.
* This ensures that the primary difference is that _ISR_Nest_level
* is 0 for task-based timers and non-zero for the others.
*/
_Thread_Disable_dispatch();
_Timer_Server_process_ticks_chain();
_Timer_Server_process_seconds_chain();
}
}
/*PAGE
*
* rtems_timer_initiate_server
*
* This directive creates and starts the server for task-based timers.
* It must be invoked before any task-based timers can be initiated.
*
* Input parameters:
* priority - timer server priority
* stack_size - stack size in bytes
* attribute_set - timer server attributes
*
* Output parameters:
* RTEMS_SUCCESSFUL - if successful
* error code - if unsuccessful
*/
rtems_status_code rtems_timer_initiate_server(
unsigned32 priority,
unsigned32 stack_size,
rtems_attribute attribute_set
)
{
rtems_id id;
rtems_status_code status;
rtems_task_priority _priority;
/*
* Make sure the requested priority is valid.
*/
_priority = priority;
if ( priority == RTEMS_TIMER_SERVER_DEFAULT_PRIORITY )
_priority = 0;
else if ( !_RTEMS_tasks_Priority_is_valid( priority ) )
return RTEMS_INVALID_PRIORITY;
/*
* Just to make sure the test versus create/start operation are atomic.
*/
_Thread_Disable_dispatch();
if ( _Timer_Server ) {
_Thread_Enable_dispatch();
return RTEMS_INCORRECT_STATE;
}
/*
* Create the Timer Server with the name the name of "TIME". The attribute
* RTEMS_SYSTEM_TASK allows us to set a priority to 0 which will makes it
* higher than any other task in the system. It can be viewed as a low
* priority interrupt. It is also always NO_PREEMPT so it looks like
* an interrupt to other tasks.
*
* We allow the user to override the default priority because the Timer
* Server can invoke TSRs which must adhere to language run-time or
* other library rules. For example, if using a TSR written in Ada the
* Server should run at the same priority as the priority Ada task.
* Otherwise, the priority ceiling for the mutex used to protect the
* GNAT run-time is violated.
*/
status = rtems_task_create(
0x4954454d, /* "TIME" */
_priority, /* create with priority 1 since 0 is illegal */
stack_size, /* let user specify stack size */
RTEMS_NO_PREEMPT, /* no preempt is like an interrupt */
/* user may want floating point but we need */
/* system task specified for 0 priority */
attribute_set | RTEMS_SYSTEM_TASK,
&id /* get the id back */
);
if (status) {
_Thread_Enable_dispatch();
return status;
}
status = rtems_task_start(
id, /* the id from create */
(rtems_task_entry) _Timer_Server_body, /* the timer server entry point */
0 /* there is no argument */
);
if (status) {
/*
* One would expect a call to rtems_task_delete() here to clean up
* but there is actually no way (in normal circumstances) that the
* start can fail. The id and starting address are known to be
* be good. If this service fails, something is weirdly wrong on the
* target such as a stray write in an ISR or incorrect memory layout.
*/
_Thread_Enable_dispatch();
return status;
}
/*
* We work with the TCB pointer, not the ID, so we need to convert
* to a TCB pointer from here out.
*
* NOTE: Setting the pointer to the Timer Server TCB to a value other than
* NULL indicates that task-based timer support is initialized.
*/
_Timer_Server = (Thread_Control *)_Objects_Get_local_object(
&_RTEMS_tasks_Information,
_Objects_Get_index(id)
);
/*
* Initialize the timer lists that the server will manage.
*/
_Chain_Initialize_empty( &_Timer_Ticks_chain );
_Chain_Initialize_empty( &_Timer_Seconds_chain );
/*
* Initialize the timers that will be used to control when the
* Timer Server wakes up and services the task-based timers.
*/
_Watchdog_Initialize( &_Timer_Server->Timer, _Thread_Delay_ended, id, NULL );
_Watchdog_Initialize( &_Timer_Seconds_timer, _Thread_Delay_ended, id, NULL );
_Thread_Enable_dispatch();
return RTEMS_SUCCESSFUL;
}
/*PAGE
*
* _Timer_Server_process_ticks_chain
*
* This routine is responsible for adjusting the list of task-based
* interval timers to reflect the passage of time.
*
* Input parameters: NONE
*
* Output parameters: NONE
*/
void _Timer_Server_process_ticks_chain(void)
{
Watchdog_Interval snapshot;
Watchdog_Interval ticks;
snapshot = _Watchdog_Ticks_since_boot;
if ( snapshot >= _Timer_Server_ticks_last_time )
ticks = snapshot - _Timer_Server_ticks_last_time;
else
ticks = (0xFFFFFFFF - _Timer_Server_ticks_last_time) + snapshot;
_Timer_Server_ticks_last_time = snapshot;
_Watchdog_Adjust( &_Timer_Ticks_chain, WATCHDOG_FORWARD, ticks );
}
/*PAGE
*
* _Timer_Server_process_seconds_chain
*
* This routine is responsible for adjusting the list of task-based
* time of day timers to reflect the passage of time.
*
* Input parameters: NONE
*
* Output parameters: NONE
*/
void _Timer_Server_process_seconds_chain(void)
{
Watchdog_Interval snapshot;
Watchdog_Interval ticks;
/*
* Process the seconds chain. Start by checking that the Time
* of Day (TOD) has not been set backwards. If it has then
* we want to adjust the _Timer_Seconds_chain to indicate this.
*/
snapshot = _TOD_Seconds_since_epoch;
if ( snapshot > _Timer_Server_seconds_last_time ) {
/*
* This path is for normal forward movement and cases where the
* TOD has been set forward.
*/
ticks = snapshot - _Timer_Server_seconds_last_time;
_Watchdog_Adjust( &_Timer_Seconds_chain, WATCHDOG_FORWARD, ticks );
} else if ( snapshot < _Timer_Server_seconds_last_time ) {
/*
* The current TOD is before the last TOD which indicates that
* TOD has been set backwards.
*/
ticks = _Timer_Server_seconds_last_time - snapshot;
_Watchdog_Adjust( &_Timer_Seconds_chain, WATCHDOG_BACKWARD, ticks );
}
_Timer_Server_seconds_last_time = snapshot;
}
