first attemtp to support Exclusive

1 files changed, 82 insertions, 0 deletions

diff --git a/examples/lock7.rs b/examples/lock7.rs
new file mode 100644
index 00000000..cdb950b8
--- /dev/null
+++ b/examples/lock7.rs
@@ -0,0 +1,82 @@
+//! 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;
+        advance(STATE, *c.resources.shared); // try swap order of (1)
+        *c.resources.shared += 3; // and (2), will fail
+        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();
+}