Panic on Peripherals access from concurrent async tasks

[Serhii-the-Dev]

When there are two parallel async tasks and each of those tasks tries to Peripherals::take() the code crashes on the very moment a second task invokes that method. It seems the issue is tied to atomics somehow however I'm not familiar nor with MCUs in general nor with ESP-IDF architecture to elaborate on that. The MCU used: ESP32-PICO-D4 on a LILYGO dev board. I have a demo program that setups a WiFi hotspot and runs UART listener in parallel, the idea is to have a board connected to another device via serial and control it from a laptop/phone for a limited timespan (kind of a first-time-setup scenario), however the panic could be reproduced on any other example which includes the parallel async tasks scenario. Here is my sample code (also adding demo.zip with a full project):

use core::convert::TryInto;

use edge_executor::LocalExecutor;
use embedded_svc::wifi::{self, AccessPointConfiguration, AuthMethod};
use esp_idf_svc::{
    eventloop::EspSystemEventLoop, hal::uart::AsyncUartRxDriver, nvs::EspDefaultNvsPartition,
    timer::EspTaskTimerService, wifi::EspWifi,
};
use esp_idf_svc::{
    hal::{
        gpio,
        prelude::Peripherals,
        task,
        timer::{TimerConfig, TimerDriver},
        uart::{self},
        units::Hertz,
    },
    wifi::AsyncWifi,
};
use futures;
use log::*;

const SSID: &str = env!("WIFI_SSID");
const PASSWORD: &str = env!("WIFI_PASS");

fn main() -> anyhow::Result<()> {
    esp_idf_svc::sys::link_patches();
    esp_idf_svc::log::EspLogger::initialize_default();

    let local_ex: LocalExecutor = Default::default();

    let wifi_task = local_ex.spawn(async move {
        let _ = setup_wifi().await;
    });

    let uart_task = local_ex.spawn(async move {
        let _ = read_uart(Hertz(400_000)).await;
    });

    task::block_on(local_ex.run(async { futures::join!(wifi_task, uart_task) }));

    Ok(())
}

async fn setup_wifi() {
    println!("Accessing peripherals");
    let peripherals = Peripherals::take().expect("Can not access peripherals");
    let sys_loop = EspSystemEventLoop::take().expect("Can not access system loop");
    let nvs = EspDefaultNvsPartition::take().expect("Can not access NVS partition");
    let timer_service = EspTaskTimerService::new().expect("Can not create task timer service");

    let mut wifi = AsyncWifi::wrap(
        EspWifi::new(peripherals.modem, sys_loop.clone(), Some(nvs))
            .expect("Can not create ESP WiFi"),
        sys_loop,
        timer_service,
    )
    .expect("Can not create WiFi");

    let wifi_configuration = wifi::Configuration::AccessPoint(AccessPointConfiguration {
        ssid: SSID.try_into().unwrap(),
        ssid_hidden: false,
        auth_method: AuthMethod::WPA2Personal,
        password: PASSWORD.try_into().unwrap(),
        ..Default::default()
    });
    wifi.set_configuration(&wifi_configuration)
        .expect("Can not set WiFi configuration");
    wifi.start().await.expect("Can not start WiFi");
    wifi.wait_netif_up()
        .await
        .expect("Can not start net interface");

    info!(
        "Created Wi-Fi with WIFI_SSID `{}` and WIFI_PASS `{}`",
        SSID, PASSWORD
    );

    println!("Initializing timer");
    let mut timer = TimerDriver::new(peripherals.timer01, &TimerConfig::new())
        .expect("Can not create timer driver");

    println!("Awaiting 10 seconds");
    timer
        .delay(timer.tick_hz() * 10)
        .await
        .expect("Can not delay");

    wifi.stop().await.expect("Can not stop WiFi");
}

async fn read_uart<'t>(baudrate: Hertz) {
    println!("Starting UART listener");
    let peripherals = Peripherals::take().unwrap();

    let rx = peripherals.pins.gpio13;
    let config = uart::config::Config::new().baudrate(baudrate);

    println!("Creating UART driver");
    let serial = AsyncUartRxDriver::new(
        peripherals.uart1,
        rx,
        Option::<gpio::Gpio0>::None,
        Option::<gpio::Gpio1>::None,
        &config,
    )
    .expect("Can not create UART driver");

    let mut buf = [0_u8; 1];

    loop {
        let _ = serial.read(&mut buf).await;
        println!("Read 0x{:02x}", buf[0]);
    }
}

The trace I have:

Starting UART listener
Guru Meditation Error: Core  0 panic'ed (Unhandled debug exception). 
Debug exception reason: BREAK instr 
Core  0 register dump:
PC      : 0x400d39c3  PS      : 0x00060336  A0      : 0x800d7e9a  A1      : 0x3ffbde30  
0x400d39c3 - async_task::raw::RawTask<F,T,S,M>::run
    at ??:??
A2      : 0x00000000  A3      : 0x400e8b78  A4      : 0x00061a80  A5      : 0x3ffbf7e4  
0x400e8b78 - core::panicking::panic_fmt
    at ??:??
A6      : 0x00000004  A7      : 0x00000001  A8      : 0x800d3309  A9      : 0x3ffbde10  
A10     : 0x00000103  A11     : 0x00000111  A12     : 0x000000ff  A13     : 0x3ffb3d78  
0x3ffb3d78 - esp_idf_hal::interrupt::ISR_YIELDER.1
    at ??:??
A14     : 0x3ffb3e94  A15     : 0x3ffbf460  SAR     : 0x00000004  EXCCAUSE: 0x00000001  
0x3ffb3e94 - std::rt::cleanup::CLEANUP
    at ??:??
EXCVADDR: 0x00000000  LBEG    : 0x4000c2e0  LEND    : 0x4000c2f6  LCOUNT  : 0x00000000  

Backtrace: 0x400d39c0:0x3ffbde30 0x400d7e97:0x3ffbded0 0x400d81ab:0x3ffbe230 0x400e118e:0x3ffbe280 0x4016a757:0x3ffbe2a0 0x4008cc61:0x3ffbe2d0

[Vollbrecht]

well take() can only called once. As it "takes out the peripheral tree", From that central struct you then hand out the handles where you need. If you call it a second time you will get a None. And since you are unwrapping it just panics

[Serhii-the-Dev]

well take() can only called once. As it "takes out the peripheral tree", From that central struct you then hand out the handles where you need. If you call it a second time you will get a None. And since you are unwrapping it just panics

Thank you, I've just put the drivers creation on top of the main with a single call to the Peripherals::take and now it's working. Sorry for a false alarm, I'm closing the issue.