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//! examples/lock.rs
#![deny(unsafe_code)]
#![deny(warnings)]
#![no_main]
#![no_std]
use cortex_m_semihosting::{debug, hprintln};
use lm3s6965::Interrupt;
use panic_semihosting as _;
use rtic::Mutex;
use rtic_core::Exclusive;
#[rtic::app(device = lm3s6965)]
const APP: () = {
struct Resources {
#[init(0)]
shared: u32,
}
#[init]
fn init(_: init::Context) {
rtic::pend(Interrupt::GPIOA);
}
// when omitted priority is assumed to be `1`
#[task(binds = GPIOA, resources = [shared])]
fn gpioa(c: gpioa::Context) {
hprintln!("A").unwrap();
// the lower priority task requires a critical section to access the data
c.resources.shared.lock(|shared| {
// data can only be modified within this critical section (closure)
*shared += 1;
// GPIOB will *not* run right now due to the critical section
rtic::pend(Interrupt::GPIOB);
hprintln!("B - shared = {}", *shared).unwrap();
// GPIOC does not contend for `shared` so it's allowed to run now
rtic::pend(Interrupt::GPIOC);
});
// critical section is over: GPIOB can now start
hprintln!("E").unwrap();
debug::exit(debug::EXIT_SUCCESS);
}
#[task(binds = GPIOB, priority = 2, resources = [shared])]
fn gpiob(c: gpiob::Context) {
c.resources.shared.lock(|shared| {
*shared += 1;
hprintln!("D - shared = {}", shared).unwrap();
});
}
#[task(binds = GPIOC, priority = 3, resources = [shared])]
fn gpioc(c: gpioc::Context) {
static mut STATE: u32 = 0;
hprintln!("GPIOC(STATE = {})", *STATE).unwrap();
*c.resources.shared += 2;
let mut ex_shared = Exclusive::new(c.resources.shared);
// a mutable exclusive is still possible to DerefMut
*ex_shared += 1;
*c.resources.shared += 3; // will fail
advance(STATE, ex_shared); // try swap order of (1)
hprintln!("GPIOC(STATE = {})", *STATE).unwrap();
}
};
// the second parameter is generic: it can be any type that implements the `Mutex` trait
fn advance(state: &mut u32, shared: impl Mutex<T = u32>) {
*state += 1;
let (old, new) = shared.lock(|shared: &mut u32| {
let old = *shared;
*shared += *state;
(old, *shared)
});
hprintln!("shared: {} -> {}", old, new).unwrap();
}
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