Detailed Description

Architecture-dependent routines declaration.

Definition in file tn_arch.h.

Functions
void	tn_arch_int_dis (void)
	Unconditionally disable interrupts.

void	tn_arch_int_en (void)
	Unconditionally enable interrupts.

TN_UWord	tn_arch_sr_save_int_dis (void)
	Disable interrupts and return previous value of status register, atomically. More...

void	tn_arch_sr_restore (TN_UWord sr)
	Restore previously saved status register. More...

TN_UWord *	_tn_arch_stack_top_get (TN_UWord *stack_low_address, int stack_size)
	Should return top of the stack, which may be either: More...

TN_UWord *	_tn_arch_stack_init (TN_TaskBody task_func, TN_UWord stack_top, void *param)
	Should put initial CPU context to the provided stack pointer for new task and return current stack pointer. More...

int	_tn_arch_inside_isr (void)
	Should return 1 if ISR is currently running, 0 otherwise.

void	_tn_arch_context_switch_pend (void)
	Called whenever we need to switch context from one task to another. More...

void	_tn_arch_context_switch_now_nosave (void)
	Called whenever we need to switch context to new task, but don't save current context. More...

Function Documentation

TN_UWord tn_arch_sr_save_int_dis ( void )

Disable interrupts and return previous value of status register, atomically.

See also: tn_arch_sr_restore()

void tn_arch_sr_restore ( TN_UWord sr )

Restore previously saved status register.

Parameters

sr	status register value previously from `tn_arch_sr_save_int_dis()`

See also: tn_arch_sr_save_int_dis()

TN_UWord* _tn_arch_stack_top_get	(	TN_UWord *	stack_low_address,
		int	stack_size
	)

Should return top of the stack, which may be either:

(stack_low_address - 1)
(stack_low_address + stack_size)

(depending on the architecture)

NOTE that returned top of the stack is NOT the address which may be used for storing the new data. Instead, it is the previous address.

Parameters

stack_low_address	start address of the stack array.
stack_size	size of the stack in `TN_UWord`-s, not in bytes.

TN_UWord* _tn_arch_stack_init	(	TN_TaskBody *	task_func,
		TN_UWord *	stack_top,
		void *	param
	)

Should put initial CPU context to the provided stack pointer for new task and return current stack pointer.

When resulting context gets restored by _tn_arch_context_switch_now_nosave() or _tn_arch_context_switch_pend(), the following conditions should be met:

Interrupts are enabled;
Return address is set to tn_task_exit(), so that when task body function returns, tn_task_exit() gets automatially called;
Argument 0 contains param pointer

Parameters

task_func	Pointer to task body function.
stack_top	Top of the stack, returned by `_tn_arch_stack_top_get()`.
param	User-provided parameter for task body function.

Returns: current stack pointer (top of the stack)

void _tn_arch_context_switch_pend ( void )

Called whenever we need to switch context from one task to another.

This function typically does NOT switch context; it merely pends it, that is, it sets appropriate interrupt flag. If current level is an application level, interrupt is fired immediately, and context gets switched.

But, if it's hard or impossible on particular platform to use dedicated interrupt flag, this function may just switch the context on its own.

Preconditions:

interrupts are enabled;
tn_curr_run_task points to currently running (preempted) task;
tn_next_task_to_run points to new task to run.

Actions to perform in actual context switching routine:

save context of the preempted task to its stack;
set tn_curr_run_task to tn_next_task_to_run;
restore context of the newly activated task from its stack.

See also: tn_curr_run_task; tn_next_task_to_run

void _tn_arch_context_switch_now_nosave ( void )

Called whenever we need to switch context to new task, but don't save current context.

This happens:

At system start, inside tn_sys_start();
At task exit, inside tn_task_exit()

This function doesn't pend context switch, it switches context immediately.

Preconditions:

interrupts are disabled;
tn_next_task_to_run is already set to needed task.

Actions to perform:

set tn_curr_run_task to tn_next_task_to_run;
restore context of the newly activated task from its stack.

See also: tn_curr_run_task; tn_next_task_to_run

Detailed Description

Functions

Function Documentation