From d5c70a3a049e087716b0cb0e9abf39c117f36586 Mon Sep 17 00:00:00 2001 From: Steins7 Date: Wed, 10 Jul 2024 21:54:23 +0200 Subject: [PATCH] Document the task module --- srv/task.c | 17 ++++++- srv/task.h | 130 +++++++++++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 142 insertions(+), 5 deletions(-) diff --git a/srv/task.c b/srv/task.c index c58e89e..818a8b5 100644 --- a/srv/task.c +++ b/srv/task.c @@ -1,9 +1,24 @@ -/** @file task.c +/** @file task.h * Module handling the task creation and management * * The module provides an API to create, run and manage lightweight, stack-less * threads (tasks). This system is based on protothreads, * see https://dunkels.com/adam/pt/index.html + * + * Task can be viewed as a lightweight, somewhat restricted, cooperative OS. + * Tasks are runned on every events. Since the RTC is enabled by the scheduler, + * every task should be run at least once per second. If at least one task is + * currently paused, the systick is enabled and all tasks are updated every + * millisecond + * + * State machine should mainly yield (see TASK_YIELD) while time sensitive + * applications should pause (see TASK_PAUSE) instead. This configuration allows + * state machines to be updated every time something changes in the system while + * allowing the cpu to enter low power mode when possible. When time sensitive + * applications are paused, they cause the systick to start which stops the cpu + * from entering low power but making sure that the task is polled quickly + * enough. Tasks requiring longer delay and less sensitive to timings can sleep + * (see TASK_SLEEP) instead, which relies on the RTC rather than the systick */ //--includes-------------------------------------------------------------------- diff --git a/srv/task.h b/srv/task.h index d242b3a..696a6dd 100644 --- a/srv/task.h +++ b/srv/task.h @@ -4,6 +4,21 @@ * The module provides an API to create, run and manage lightweight, stack-less * threads (tasks). This system is based on protothreads, * see https://dunkels.com/adam/pt/index.html + * + * Task can be viewed as a lightweight, somewhat restricted, cooperative OS. + * Tasks are runned on every events. Since the RTC is enabled by the scheduler, + * every task should be run at least once per second. If at least one task is + * currently paused, the systick is enabled and all tasks are updated every + * millisecond + * + * State machine should mainly yield (see TASK_YIELD) while time sensitive + * applications should pause (see TASK_PAUSE) instead. This configuration allows + * state machines to be updated every time something changes in the system while + * allowing the cpu to enter low power mode when possible. When time sensitive + * applications are paused, they cause the systick to start which stops the cpu + * from entering low power but making sure that the task is polled quickly + * enough. Tasks requiring longer delay and less sensitive to timings can sleep + * (see TASK_SLEEP) instead, which relies on the RTC rather than the systick */ #ifndef _task_h_ @@ -17,6 +32,9 @@ //--type definitions------------------------------------------------------------ +/** + * Available triggers for a task + */ enum TaskTrigger { TASK_TRIGGER_ANY, TASK_TRIGGER_STK, @@ -24,15 +42,26 @@ enum TaskTrigger { TASK_TRIGGER_BOTH, }; +/** + * State of a task at any given time. Every single task is described by such a + * struct + */ struct TaskState { - uint32_t timestamp; - uint8_t count:5; - enum TaskTrigger trigger:2; - uint8_t timeout_mode:1; + uint32_t timestamp; //timestamp at wich to wakeup the task, if any + uint8_t count:5; //task counter: active step of task + enum TaskTrigger trigger:2; //triggers on wich to execute the task + uint8_t timeout_mode:1; //whether the timestamp is a timeout or a delay }; +/** + * Function prototype of tasks + */ typedef void(*TaskFunction)(struct TaskState*, uint32_t); +/** + * Full definition of a task. Contains the function supporting the task as well + * as the state of said task + */ struct Task { TaskFunction function; struct TaskState state; @@ -41,40 +70,133 @@ struct Task { //--functions------------------------------------------------------------------- +/** + * Task declaration macro, to be used to declare and define a task instead of a + * regular function declaration/defintion + */ #define TASK(fct_name) void fct_name(struct TaskState* restrict __task_state, \ uint32_t __task_time) +/** + * Task entry macro, must be present at the begin of every task. Setup code to + * be run indepently of the task state may be put before that (static variables, + * init code, ...) + */ #define TASK_ENTRY \ _TASK_COUNT_INIT; \ (void*) __task_time; \ switch (__task_state->count) { +/** + * Task cleanup macro. Option, can be use right before TASK_EXIT. This step + * will be executed before exiting the task when task_stop() is called. As the + * name suggest, this is mainly usefull to implement cleanup code and allow for + * gracefull shutdowns + */ #define TASK_CLEANUP \ case (_TASK_COUNT_CLEANUP): \ /* fall through */ +/** + * Tasks exit macro, must be present at the end of every task. Any code written + * after that will never be executed + */ #define TASK_EXIT \ } \ __task_state->count = _TASK_COUNT_EXIT & 0x1F; \ return; +/** + * Returns whether the task was timed-out or not. This macro can be used after + * TASK_PAUSE_UNTIL and TASK_SLEEP_UNTIL to know if the task resumed because of + * the condition or because of the timeout. Does not correspond to anything + * when called after any other step + */ #define TASK_TIMEOUT (__task_state->timeout == 0) +/** + * Give up the cpu, allowing the other tasks to run. The task will resume at the + * next event. Between events, the cpu can enter various power saving states + * depending on the other tasks running + */ #define TASK_YIELD() _TASK_YIELD(_TASK_COUNT_INCR) + +/** + * Suspend the task for the specified amount of milliseconds. The systick will + * remain active while the task is suspended to provide milliseconds counting, + * limiting the ability of the cpu to save power + */ #define TASK_PAUSE(delay_ms) _TASK_PAUSE(delay_ms, _TASK_COUNT_INCR) + +/** + * Suspend the task for the specified amount of seconds. The RTC will be used to + * provide seconds counting. If no other tasks requires it, the systick is + * disabled to save more power + */ #define TASK_SLEEP(delay_s) _TASK_SLEEP(delay_s, _TASK_COUNT_INCR) + +/** + * Execute TASK_YIELD until the provided condition is reached. The condition + * will be checked on every event + */ #define TASK_YIELD_UNTIL(cond) _TASK_YIELD_UNTIL(cond, _TASK_COUNT_INCR) + +/** + * Execute TASK_PAUSE until either the condition or the delay is reached. + * TASK_TIMEOUT can be used to know what cause the task to resume. The condition + * will be checked every millisecond + */ #define TASK_PAUSE_UNTIL(cond, delay_ms) \ _TASK_PAUSE_UNTIL(cond, delay_ms, _TASK_COUNT_INCR) + +/** + * Execute TASK_SLEEP until either the condition or the delay is reached. + * TASK_TIMEOUT can be used to know what cause the task to resume. The condition + * will be checked every seconds + */ #define TASK_SLEEP_UNTIL(cond, delay_s) \ _TASK_SLEEP_UNTIL(cond, delay_s, _TASK_COUNT_INCR) + +/** + * Execute the specified task, suspending the current one until the task exits + */ #define TASK_EXECUTE(task) _TASK_EXECUTE(task, _TASK_COUNT_INCR) +/** + * Starts the task scheduler and run it until the system is shutdown. This + * function never returns. + * + * All tasks started using task_start() are run according to their current + * state (see TASK_* macros). Since this system is cooperative, the scheduler + * does not preempt the tasks when running. The RTC is automatically configured + * and started to provide events every seconds. The systick is automatically + * started and stop to provide events every milliseconds when needed + */ void task_start_scheduler(void); + +/** + * Returns the current system time. The epoc is undefined. The time is provided + * in milliseconds, though the millisecond precision is only available while the + * systick is running (at least one task paused) + */ uint32_t task_current_time(void); +/** + * Starts the specified task. The task will only trully be runned after + * task_start_scheduler() is called. + * A task already started will be left as-is + */ void task_start(TaskFunction task); + +/** + * Stops the specified task. The task's cleanup state will be executed before + * it exits + */ void task_stop(TaskFunction task); + +/** + * Returns whether the specified task is currently running or not + */ bool task_is_running(TaskFunction task);