From 9f80c9b916e93187e755750e8aff4b9c363ef507 Mon Sep 17 00:00:00 2001
From: Per Lindgren <per.lindgren@ltu.se>
Date: Mon, 15 Jun 2020 23:31:30 +0200
Subject: [PATCH] now with the very exclusive feature link_fail

---
 Cargo.toml              |  6 ++-
 examples/lock5_mutex.rs | 85 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 89 insertions(+), 2 deletions(-)
 create mode 100644 examples/lock5_mutex.rs

diff --git a/Cargo.toml b/Cargo.toml
index 97d8d8700d..58b54feaf2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -57,11 +57,11 @@ version = '0.5.3'
 [lib]
 name = 'rtic'
 
-# path = "../rtic-core"
-
+# path = '../rtic-core'
 [patch.crates-io.rtic-core]
 git = 'https://github.com/rtic-rs/rtic-core.git'
 branch = 'immutable_resource_proxies'
+             
 
 [dependencies]
 cortex-m = '0.6.2'
@@ -99,6 +99,8 @@ heterogeneous = [
 homogeneous = ['cortex-m-rtic-macros/homogeneous']
 __v7 = []
 __min_r1_43 = []
+link_fail = ['rtic-core/link_fail']
+
 [profile.release]
 codegen-units = 1
 lto = true
diff --git a/examples/lock5_mutex.rs b/examples/lock5_mutex.rs
new file mode 100644
index 0000000000..f43f2ec6c9
--- /dev/null
+++ b/examples/lock5_mutex.rs
@@ -0,0 +1,85 @@
+//! 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) {
+        static mut STATE: u32 = 28;
+        c.resources.shared.lock(|shared| {
+            *shared += 1;
+            hprintln!("D - shared = {}", shared).unwrap();
+        });
+        advance(STATE, c.resources.shared);
+    }
+
+    #[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 ex_shared = Exclusive::new(c.resources.shared);
+        advance(STATE, ex_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();
+}