Due to the dual core nature of the ESP32, there are instances where a certain function must be run in the context of a particular core (e.g. allocating ISR to an interrupt source of a particular core). The IPC (Inter-Processor Call) feature allows for the execution of functions on a particular CPU.
A given function can be executed on a particular core by calling :cpp:func:`esp_ipc_call` or :cpp:func:`esp_ipc_call_blocking`. IPC is implemented via two high priority FreeRTOS tasks pinned to each CPU known as the IPC Tasks. The two IPC Tasks remain inactive (blocked) until :cpp:func:`esp_ipc_call` or :cpp:func:`esp_ipc_call_blocking` is called. When an IPC Task of a particular core is unblocked, it will preempt the current running task on that core and execute a given function.
:cpp:func:`esp_ipc_call` unblocks the IPC task on a particular core to execute a given function. The task that calls :cpp:func:`esp_ipc_call` will be blocked until the IPC Task begins execution of the given function. :cpp:func:`esp_ipc_call_blocking` is similar but will block the calling task until the IPC Task has completed execution of the given function.
Functions executed by IPCs must be functions of type void func(void *arg). To run more complex functions which require a larger stack, the IPC tasks' stack size can be configured by modifying :ref:`CONFIG_ESP_IPC_TASK_STACK_SIZE` in menuconfig. The IPC API is protected by a mutex hence simultaneous IPC calls are not possible.
Care should taken to avoid deadlock when writing functions to be executed by IPC, especially when attempting to take a mutex within the function.