rtic/src/examples/_4_nested.rs

//! Nesting claims and how the preemption threshold works
//!
//! If you run this program you'll hit the breakpoints as indicated by the
//! letters in the comments: A, then B, then C, etc.
//!
//! ```
//! #![deny(unsafe_code)]
//! #![feature(const_fn)]
//! #![feature(proc_macro)]
//! #![no_std]
//! 
//! extern crate cortex_m_rtfm as rtfm;
//! extern crate stm32f103xx;
//! 
//! use stm32f103xx::Interrupt;
//! use rtfm::{app, Resource, Threshold};
//! 
//! app! {
//!     device: stm32f103xx,
//! 
//!     resources: {
//!         static LOW: u64 = 0;
//!         static HIGH: u64 = 0;
//!     },
//! 
//!     tasks: {
//!         EXTI0: {
//!             path: exti0,
//!             priority: 1,
//!             resources: [LOW, HIGH],
//!         },
//! 
//!         EXTI1: {
//!             path: exti1,
//!             priority: 2,
//!             resources: [LOW],
//!         },
//! 
//!         EXTI2: {
//!             path: exti2,
//!             priority: 3,
//!             resources: [HIGH],
//!         },
//!     },
//! }
//! 
//! fn init(_p: init::Peripherals, _r: init::Resources) {}
//! 
//! fn idle() -> ! {
//!     // A
//!     rtfm::bkpt();
//! 
//!     // Sets task `exti0` as pending
//!     //
//!     // Because `exti0` has higher priority than `idle` it will be executed
//!     // immediately
//!     rtfm::set_pending(Interrupt::EXTI0); // ~> exti0
//! 
//!     loop {
//!         rtfm::wfi();
//!     }
//! }
//! 
//! fn exti0(t: &mut Threshold, r: EXTI0::Resources) {
//!     // Because this task has a priority of 1 the preemption threshold `t` also
//!     // starts at 1
//! 
//!     let mut low = r.LOW;
//!     let mut high = r.HIGH;
//! 
//!     // B
//!     rtfm::bkpt();
//! 
//!     // Because `exti1` has higher priority than `exti0` it can preempt it
//!     rtfm::set_pending(Interrupt::EXTI1); // ~> exti1
//! 
//!     // A claim creates a critical section
//!     low.claim_mut(t, |_low, t| {
//!         // This claim increases the preemption threshold to 2
//!         //
//!         // 2 is just high enough to not race with task `exti1` for access to the
//!         // `LOW` resource
//! 
//!         // D
//!         rtfm::bkpt();
//! 
//!         // Now `exti1` can't preempt this task because its priority is equal to
//!         // the current preemption threshold
//!         rtfm::set_pending(Interrupt::EXTI1);
//! 
//!         // But `exti2` can, because its priority is higher than the current
//!         // preemption threshold
//!         rtfm::set_pending(Interrupt::EXTI2); // ~> exti2
//! 
//!         // F
//!         rtfm::bkpt();
//! 
//!         // Claims can be nested
//!         high.claim_mut(t, |_high, _| {
//!             // This claim increases the preemption threshold to 3
//! 
//!             // Now `exti2` can't preempt this task
//!             rtfm::set_pending(Interrupt::EXTI2);
//! 
//!             // G
//!             rtfm::bkpt();
//!         });
//! 
//!         // Upon leaving the critical section the preemption threshold drops back
//!         // to 2 and `exti2` immediately preempts this task
//!         // ~> exti2
//!     });
//! 
//!     // Once again the preemption threshold drops but this time to 1. Now the
//!     // pending `exti1` task can preempt this task
//!     // ~> exti1
//! }
//! 
//! fn exti1(_t: &mut Threshold, _r: EXTI1::Resources) {
//!     // C, I
//!     rtfm::bkpt();
//! }
//! 
//! fn exti2(_t: &mut Threshold, _r: EXTI2::Resources) {
//!     // E, H
//!     rtfm::bkpt();
//! }
//! ```
// Auto-generated. Do not modify.