1 files changed, 71 insertions, 0 deletions
diff --git a/examples/lock.rs b/examples/lock.rs
new file mode 100644
index 00000000..097bd5c3
--- /dev/null
+++ b/examples/lock.rs
@@ -0,0 +1,71 @@
+//! examples/lock.rs
+
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+extern crate panic_semihosting;
+
+use cortex_m_semihosting::debug;
+use lm3s6965::Interrupt;
+use rtfm::app;
+
+macro_rules! println {
+    ($($tt:tt)*) => {
+        if let Ok(mut stdout) = cortex_m_semihosting::hio::hstdout() {
+            use core::fmt::Write;
+
+            writeln!(stdout, $($tt)*).ok();
+        }
+    };
+}
+
+#[app(device = lm3s6965)]
+const APP: () = {
+    static mut SHARED: u32 = 0;
+
+    #[init]
+    fn init() {
+        rtfm::pend(Interrupt::GPIOA);
+    }
+
+    // when omitted priority is assumed to be `1`
+    #[interrupt(resources = [SHARED])]
+    fn GPIOA() {
+        println!("A");
+
+        // the lower priority task requires a critical section to access the data
+        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
+            rtfm::pend(Interrupt::GPIOB);
+
+            println!("B - SHARED = {}", *shared);
+
+            // GPIOC does not contend for `SHARED` so it's allowed to run now
+            rtfm::pend(Interrupt::GPIOC);
+        });
+
+        // critical section is over: GPIOB can now start
+
+        println!("E");
+
+        debug::exit(debug::EXIT_SUCCESS);
+    }
+
+    #[interrupt(priority = 2, resources = [SHARED])]
+    fn GPIOB() {
+        // the higher priority task does *not* need a critical section
+        *resources.SHARED += 1;
+
+        println!("D - SHARED = {}", *resources.SHARED);
+    }
+
+    #[interrupt(priority = 3)]
+    fn GPIOC() {
+        println!("C");
+    }
+};