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 esp_execute_shared_stack_function(), passing that function as parameter.
Usage
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 will be 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:
void external_stack_function(void)
{
printf("Executing this printf from external stack! \n");
}
//Let's 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:
portSTACK_TYPE *shared_stack = malloc(8192 * sizeof(portSTACK_TYPE));
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);
}
API Reference
Header File
Functions
Calls user defined shared stack space function.
Note
if either lock, stack or stack size is invalid, the expression will be called using the current stack.
- Parameters
lock – Mutex object to protect in case of shared stack
stack – Pointer to user alocated stack
stack_size – Size of current stack in bytes
function – pointer to the shared stack function to be executed
Macros
-
ESP_EXECUTE_EXPRESSION_WITH_STACK(lock, stack, stack_size, expression)