esp-idf/docs/en/api-reference/system/esp_function_with_shared_stack.rst

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Call Function with External Stack
=================================
Overview
--------
A given function can be executed with a user-allocated stack space which is independent of current task stack, this mechanism can be used to save stack space wasted by tasks which call a common function with intensive stack usage such as ``printf``. The given function can be called inside the shared stack space which is a callback function deferred by calling :cpp:func:`esp_execute_shared_stack_function`, passing that function as a parameter.
Usage
-----
:cpp:func:`esp_execute_shared_stack_function` takes four arguments:
- a mutex object allocated by the caller, which is used to protect if the same function shares its allocated stack
- a pointer to the top of stack used for that function
- the size of stack in bytes
- a pointer to the shared stack function
The user-defined function is deferred as a callback and can be called using the user-allocated space without taking space from current task stack.
The usage may look like the code below:
.. code-block:: c
void external_stack_function(void)
{
printf("Executing this printf from external stack! \n");
}
//Let us suppose we want to call printf using a separated stack space
//allowing the app to reduce its stack size.
void app_main()
{
//Allocate a stack buffer, from heap or as a static form:
StackType_t *shared_stack = malloc(8192 * sizeof(StackType_t));
assert(shared_stack != NULL);
//Allocate a mutex to protect its usage:
SemaphoreHandle_t printf_lock = xSemaphoreCreateMutex();
assert(printf_lock != NULL);
//Call the desired function using the macro helper:
esp_execute_shared_stack_function(printf_lock,
shared_stack,
8192,
external_stack_function);
vSemaphoreDelete(printf_lock);
free(shared_stack);
}
.. _esp-call-with-stack-basic_usage:
API Reference
-------------
.. include-build-file:: inc/esp_expression_with_stack.inc