ICARUS Scheduler - Task Scheduling and Timing. More...

#include <stdint.h>
#include "icarus/types.h"

Functions
void	os_yield (void)
	Voluntarily yield CPU to scheduler.

uint32_t	task_active_sleep (uint32_t ticks)
	Sleep for specified ticks (cooperative)

uint32_t	task_blocking_sleep (uint32_t ticks)
	Sleep with scheduler disabled (blocking)

uint32_t	task_busy_wait (uint32_t ticks)
	Busy-wait for specified ticks.

uint32_t	os_get_tick_count (void)
	Get current system tick count.

uint8_t	os_get_running_task_count (void)
	Get number of active tasks.

const char *	os_get_current_task_name (void)
	Get name of currently executing task.

uint32_t	os_get_task_ticks_remaining (void)
	Get remaining ticks in current time slice.

const char *	os_get_task_name (uint8_t task_idx)
	Get task name by index (safe from unprivileged mode)

uint8_t	os_get_num_created_tasks (void)
	Get number of created tasks (safe from unprivileged mode)

uint8_t	os_is_running (void)
	Check if OS is running (safe from unprivileged mode)

icarus_task_state_t	os_get_task_state (uint8_t task_idx)
	Get a task's current state (safe from unprivileged mode).

uint32_t	os_get_task_dispatch_count (uint8_t task_idx)
	Get a task's dispatch count (times scheduled to run).

uint32_t	os_get_stack_watermark (uint8_t task_idx)
	Get a task's stack high-water mark (minimum free words).

void	os_update_stack_watermark (uint8_t task_idx)
	Scan a task's stack for the sentinel pattern and update the watermark field in the TCB.

void	__os_yield (void)
	Privileged implementation of os_yield.

uint32_t	__task_active_sleep (uint32_t ticks)
	Privileged implementation of task_active_sleep.

uint32_t	__task_blocking_sleep (uint32_t ticks)
	Privileged implementation of task_blocking_sleep.

uint32_t	__task_busy_wait (uint32_t ticks)
	Privileged implementation of task_busy_wait.

uint32_t	__os_get_tick_count (void)
	Privileged implementation of os_get_tick_count.

uint8_t	__os_get_running_task_count (void)
	Privileged implementation of os_get_running_task_count.

const char *	__os_get_current_task_name (void)
	Privileged implementation of os_get_current_task_name.

uint32_t	__os_get_task_ticks_remaining (void)
	Privileged implementation of os_get_task_ticks_remaining.

const char *	__os_get_task_name (uint8_t task_idx)
	Privileged implementation of os_get_task_name.

uint8_t	__os_get_num_created_tasks (void)
	Privileged implementation of os_get_num_created_tasks.

uint8_t	__os_is_running (void)
	Privileged implementation of os_is_running.

icarus_task_state_t	__os_get_task_state (uint8_t task_idx)
	Privileged implementation of os_get_task_state.

uint32_t	__os_get_task_dispatch_count (uint8_t task_idx)
	Privileged implementation of os_get_task_dispatch_count.

uint32_t	__os_get_stack_watermark (uint8_t task_idx)
	Privileged implementation of os_get_stack_watermark.

void	__os_update_stack_watermark (uint8_t task_idx)
	Scan a task's stack from the base upward for the sentinel pattern (0xDEADC0DE) and update the watermark.

Detailed Description

ICARUS Scheduler - Task Scheduling and Timing.

Version: 0.1.0

Task scheduling, yielding, and sleep functions.

Author: Souham Biswas

Date: 2025

Copyright: Copyright 2025-2026 Souham Biswas https://github.com/ironhide23586/icarus-os-core Licensed under the Apache License, Version 2.0

Definition in file scheduler.h.

Function Documentation

◆ __os_get_current_task_name()

const char * __os_get_current_task_name ( void )

Privileged implementation of os_get_current_task_name.

Note: Internal function - use os_get_current_task_name() wrapper; Copies name from DTCM to RAM_D1 buffer for unprivileged access

Definition at line 65 of file scheduler.c.

References current_task_index, ICARUS_MAX_TASK_NAME_LEN, icarus_task_t::name, num_created_tasks, task_list, and task_name_buffer.

Referenced by os_get_current_task_name(), and SVC_Handler_C().

◆ __os_get_num_created_tasks()

uint8_t __os_get_num_created_tasks ( void )

Privileged implementation of os_get_num_created_tasks.

Note: Internal function - use os_get_num_created_tasks() wrapper; Runs in SVC handler — reads num_created_tasks from DTCM in privileged mode

Definition at line 345 of file kernel.c.

References num_created_tasks.

Referenced by os_get_num_created_tasks(), and SVC_Handler_C().

◆ __os_get_running_task_count()

uint8_t __os_get_running_task_count ( void )

Privileged implementation of os_get_running_task_count.

Note: Internal function - use os_get_running_task_count() wrapper

Definition at line 56 of file scheduler.c.

References running_task_count.

Referenced by os_get_running_task_count(), and SVC_Handler_C().

◆ __os_get_stack_watermark()

uint32_t __os_get_stack_watermark ( uint8_t task_idx )

Privileged implementation of os_get_stack_watermark.

Parameters

task_idx Task index.

Returns: Minimum free stack words observed.

Definition at line 387 of file kernel.c.

References num_created_tasks, icarus_task_t::stack_watermark, and task_list.

Referenced by os_get_stack_watermark(), and SVC_Handler_C().

◆ __os_get_task_dispatch_count()

uint32_t __os_get_task_dispatch_count ( uint8_t task_idx )

Privileged implementation of os_get_task_dispatch_count.

Parameters

task_idx Task index.

Returns: Dispatch count.

Definition at line 375 of file kernel.c.

References icarus_task_t::dispatch_count, num_created_tasks, and task_list.

Referenced by os_get_task_dispatch_count(), and SVC_Handler_C().

◆ __os_get_task_name()

const char * __os_get_task_name ( uint8_t task_idx )

Privileged implementation of os_get_task_name.

Note: Internal function - use os_get_task_name() wrapper; Runs in SVC handler — reads task_list from DTCM in privileged mode; Copies name to RAM_D1 buffer to allow unprivileged access

Definition at line 315 of file kernel.c.

References ICARUS_MAX_TASK_NAME_LEN, icarus_task_t::name, num_created_tasks, and task_list.

Referenced by os_get_task_name(), and SVC_Handler_C().

◆ __os_get_task_state()

icarus_task_state_t __os_get_task_state ( uint8_t task_idx )

Privileged implementation of os_get_task_state.

Parameters

task_idx Task index.

Returns: Task state enum value.

Definition at line 363 of file kernel.c.

References num_created_tasks, task_list, icarus_task_t::task_state, and TASK_STATE_FINISHED.

Referenced by os_get_task_state(), and SVC_Handler_C().

◆ __os_get_task_ticks_remaining()

uint32_t __os_get_task_ticks_remaining ( void )

Privileged implementation of os_get_task_ticks_remaining.

Note: Internal function - use os_get_task_ticks_remaining() wrapper

Definition at line 87 of file scheduler.c.

References current_task_ticks_remaining.

Referenced by os_get_task_ticks_remaining(), and SVC_Handler_C().

◆ __os_get_tick_count()

uint32_t __os_get_tick_count ( void )

Privileged implementation of os_get_tick_count.

Note: Internal function - use os_get_tick_count() wrapper

Definition at line 48 of file scheduler.c.

References os_tick_count.

Referenced by os_get_tick_count(), and SVC_Handler_C().

◆ __os_is_running()

uint8_t __os_is_running ( void )

Privileged implementation of os_is_running.

Note: Internal function - use os_is_running() wrapper; Runs in SVC handler — reads os_running from DTCM in privileged mode

Definition at line 354 of file kernel.c.

References os_running.

Referenced by os_is_running(), and SVC_Handler_C().

◆ __os_update_stack_watermark()

void __os_update_stack_watermark ( uint8_t task_idx )

Scan a task's stack from the base upward for the sentinel pattern (0xDEADC0DE) and update the watermark.

Parameters

task_idx Task index.

Definition at line 399 of file kernel.c.

References num_created_tasks, icarus_task_t::stack_base, icarus_task_t::stack_size, icarus_task_t::stack_watermark, and task_list.

Referenced by os_update_stack_watermark(), and SVC_Handler_C().

◆ __os_yield()

void __os_yield ( void )

Privileged implementation of os_yield.

Note: Internal function - use os_yield() wrapper

Definition at line 99 of file scheduler.c.

References current_task_ticks_remaining, and ticks_per_task.

Referenced by __os_exit_task(), __os_kill_process(), __task_active_sleep(), os_yield(), and SVC_Handler_C().

◆ __task_active_sleep()

uint32_t __task_active_sleep ( uint32_t ticks )

Privileged implementation of task_active_sleep.

Note: Internal function - use task_active_sleep() wrapper

Definition at line 108 of file scheduler.c.

References __os_yield(), current_task_index, icarus_task_t::global_tick_paused, os_tick_count, task_list, icarus_task_t::task_state, TASK_STATE_BLOCKED, and icarus_task_t::ticks_to_pause.

Referenced by SVC_Handler_C(), and task_active_sleep().

◆ __task_blocking_sleep()

uint32_t __task_blocking_sleep ( uint32_t ticks )

Privileged implementation of task_blocking_sleep.

Note: Internal function - use task_blocking_sleep() wrapper; Spin-wait calls public SVC wrappers — only safe from thread mode

Definition at line 121 of file scheduler.c.

References enter_critical(), exit_critical(), and task_busy_wait().

Referenced by task_blocking_sleep().

◆ __task_busy_wait()

uint32_t __task_busy_wait ( uint32_t ticks )

Privileged implementation of task_busy_wait.

Note: Internal function - use task_busy_wait() wrapper; Uses os_get_tick_count() SVC gate — safe with DTCM priv-only

Definition at line 133 of file scheduler.c.

References os_get_tick_count(), and os_tick_count.

Referenced by task_busy_wait().

◆ os_get_current_task_name()

const char * os_get_current_task_name ( void )

Get name of currently executing task.

Returns: Task name string or "unknown"

Definition at line 575 of file svc.c.

◆ os_get_num_created_tasks()

uint8_t os_get_num_created_tasks ( void )

Get number of created tasks (safe from unprivileged mode)

Returns: Number of tasks registered with os_register_task()

Note: Uses SVC to read num_created_tasks from DTCM in privileged mode

Get number of created tasks (safe from unprivileged mode)

Returns: Number of tasks registered with os_register_task()

Note: Safe to call from unprivileged mode once DTCM is priv-only

Definition at line 1145 of file svc.c.

References __os_get_num_created_tasks(), and SVC_GET_NUM_TASKS.

Referenced by display_init().

◆ os_get_running_task_count()

uint8_t os_get_running_task_count ( void )

Get number of active tasks.

Returns: Count of tasks in RUNNING/READY/BLOCKED state

Definition at line 594 of file svc.c.

References __os_get_running_task_count(), and SVC_OS_GET_RUNNING_TASK_COUNT.

◆ os_get_stack_watermark()

uint32_t os_get_stack_watermark ( uint8_t task_idx )

Get a task's stack high-water mark (minimum free words).

Parameters

task_idx Task index.

Returns: Minimum free stack words observed, or 0 if invalid.

Note: The watermark is updated lazily — call os_update_stack_watermark() to force a scan.

Get a task's stack high-water mark (minimum free words).

Definition at line 1225 of file svc.c.

References __os_get_stack_watermark(), and SVC_GET_STACK_WATERMARK.

◆ os_get_task_dispatch_count()

uint32_t os_get_task_dispatch_count ( uint8_t task_idx )

Get a task's dispatch count (times scheduled to run).

Parameters

task_idx Task index.

Returns: Dispatch count, or 0 if index is invalid.

Get a task's dispatch count (times scheduled to run).

Definition at line 1205 of file svc.c.

References __os_get_task_dispatch_count(), and SVC_GET_TASK_DISPATCH_COUNT.

◆ os_get_task_name()

const char * os_get_task_name ( uint8_t task_idx )

Get task name by index (safe from unprivileged mode)

Parameters

task_idx Task index (0 to num_created_tasks-1)

Returns: Pointer to task name string, or NULL if invalid index

Note: Uses SVC to read task_list from DTCM in privileged mode

Get task name by index (safe from unprivileged mode)

Parameters

task_idx Task index (0 to num_created_tasks-1)

Returns: Pointer to task name string, or NULL if invalid index

Note: Safe to call from unprivileged mode once DTCM is priv-only

Definition at line 1123 of file svc.c.

References __os_get_task_name(), and SVC_GET_TASK_NAME.

Referenced by display_init().

◆ os_get_task_state()

icarus_task_state_t os_get_task_state ( uint8_t task_idx )

Get a task's current state (safe from unprivileged mode).

Parameters

task_idx Task index (0 to num_created_tasks-1).

Returns: Task state, or TASK_STATE_FINISHED if index is invalid.

Note: Uses SVC to read task_list from DTCM in privileged mode.

Get a task's current state (safe from unprivileged mode).

Definition at line 1185 of file svc.c.

References __os_get_task_state(), and SVC_GET_TASK_STATE.

◆ os_get_task_ticks_remaining()

uint32_t os_get_task_ticks_remaining ( void )

Get remaining ticks in current time slice.

Returns: Ticks remaining before preemption

Definition at line 613 of file svc.c.

References __os_get_task_ticks_remaining(), and SVC_OS_GET_TASK_TICKS_REMAINING.

◆ os_get_tick_count()

uint32_t os_get_tick_count ( void )

Get current system tick count.

Returns: Ticks since os_start()

Note: Placed in ITCM for zero wait-state execution

Definition at line 556 of file svc.c.

References __os_get_tick_count(), and SVC_OS_GET_TICK_COUNT.

Referenced by __task_busy_wait().

◆ os_is_running()

uint8_t os_is_running ( void )

Check if OS is running (safe from unprivileged mode)

Returns: 1 if OS is running, 0 otherwise

Note: Uses SVC to read os_running from DTCM in privileged mode

Returns: 1 if OS is running, 0 otherwise

Note: Safe to call from unprivileged mode once DTCM is priv-only

Definition at line 1166 of file svc.c.

References __os_is_running(), and SVC_OS_IS_RUNNING.

Referenced by os_heartbeat_task().

◆ os_update_stack_watermark()

void os_update_stack_watermark ( uint8_t task_idx )

Scan a task's stack for the sentinel pattern and update the watermark field in the TCB.

Parameters

task_idx Task index.

Scan a task's stack for the sentinel pattern and update the watermark field in the TCB.

Definition at line 1245 of file svc.c.

References __os_update_stack_watermark(), and SVC_UPDATE_STACK_WATERMARK.

◆ os_yield()

void os_yield ( void )

Voluntarily yield CPU to scheduler.

Note: Placed in ITCM for zero wait-state execution

Definition at line 511 of file svc.c.

◆ task_active_sleep()

uint32_t task_active_sleep ( uint32_t ticks )

Sleep for specified ticks (cooperative)

Parameters

ticks Number of ticks to sleep

Returns: Actual ticks elapsed

Note: Placed in ITCM for zero wait-state execution

Sleep for specified ticks (cooperative)

Definition at line 522 of file svc.c.

◆ task_blocking_sleep()

uint32_t task_blocking_sleep ( uint32_t ticks )

Sleep with scheduler disabled (blocking)

Parameters

ticks Number of ticks to wait

Returns: Actual ticks elapsed

Warning: Blocks all other tasks!

Sleep with scheduler disabled (blocking)

Definition at line 542 of file svc.c.

References __task_blocking_sleep().

Referenced by __io_putchar().

◆ task_busy_wait()

uint32_t task_busy_wait ( uint32_t ticks )

Busy-wait for specified ticks.

Parameters

ticks Number of ticks to wait

Returns: Actual ticks elapsed

Busy-wait for specified ticks.

Definition at line 549 of file svc.c.

References __task_busy_wait().

Referenced by __task_blocking_sleep().

Functions

Detailed Description

Function Documentation

◆ __os_get_current_task_name()

◆ __os_get_num_created_tasks()

◆ __os_get_running_task_count()

◆ __os_get_stack_watermark()

◆ __os_get_task_dispatch_count()

◆ __os_get_task_name()

◆ __os_get_task_state()

◆ __os_get_task_ticks_remaining()

◆ __os_get_tick_count()

◆ __os_is_running()

◆ __os_update_stack_watermark()

◆ __os_yield()

◆ __task_active_sleep()

◆ __task_blocking_sleep()

◆ __task_busy_wait()

◆ os_get_current_task_name()

◆ os_get_num_created_tasks()

◆ os_get_running_task_count()

◆ os_get_stack_watermark()

◆ os_get_task_dispatch_count()

◆ os_get_task_name()

◆ os_get_task_state()

◆ os_get_task_ticks_remaining()

◆ os_get_tick_count()

◆ os_is_running()

◆ os_update_stack_watermark()

◆ os_yield()

◆ task_active_sleep()

◆ task_blocking_sleep()

◆ task_busy_wait()