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 a 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 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:
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);
}
API Reference
Header File
This header file can be included with:
#include "esp_expression_with_stack.h"
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)