book/resources: do not use the lock API in the very first example

instead stick to `#[local]` resources

book/en/src/by-example/resources.md

@@ -7,9 +7,11 @@ Resources are data visible only to functions declared within the `#[app]`
 module. The framework gives the user complete control over which context
 can access which resource.
 
-All resources are declared as a single `struct` within the `#[app]`
+All resources are declared as *two* `struct`s within the `#[app]` module.
-module. Each field in the structure corresponds to a different resource.
+Each field in these structures corresponds to a different resource.
-The `struct` must be annotated with the following attribute: `#[resources]`.
+One `struct` must be annotated with the attribute `#[local]`.
+The other `struct` must be annotated with the attribute `#[shared]`.
+The difference between these two sets of resources will be covered later.
 
 Resources can optionally be given an initial value using the `#[init]`
 attribute. Resources that are not given an initial value are referred to as
@@ -17,12 +19,13 @@ attribute. Resources that are not given an initial value are referred to as
 page.
 
 Each context (task handler, `init` or `idle`) must declare the resources it
-intends to access in its corresponding metadata attribute using the `resources`
+intends to access in its corresponding metadata attribute using either the
-argument. This argument takes a list of resource names as its value. The listed
+`local` or `shared` argument. This argument takes a list of resource names as
-resources are made available to the context under the `resources` field of the
+its value. The listed resources are made available to the context under the
-`Context` structure.
+`local` and `shared` fields of the `Context` structure.
 
-The example application shown below contains two interrupt handlers that share access to a resource named `shared`.
+The example application shown below contains two interrupt handlers.
+Each handler has access to its own `#[local]` resource.
 
 ``` rust
 {{#include ../../../../examples/resource.rs}}
@@ -33,13 +36,14 @@ $ cargo run --example resource
 {{#include ../../../../ci/expected/resource.run}}
 ```
 
-Note that the `shared` resource cannot be accessed from `idle`. Attempting to do so results in a compile error.
+A `#[local]` resource cannot be accessed from outside the task it was associated to in a `#[task]` attribute.
+Assigning the same `#[local]` resource to more than one task is a compile-time error.
 
 ## `lock`
 
-Critical sections are required to access shared mutable data in a data race-free manner.
+Critical sections are required to access `#[shared]` resources in a data race-free manner.
 
-The `resources` field of the passed `Context` implements the [`Mutex`] trait for each shared resource accessible to the task.
+The `shared` field of the passed `Context` implements the [`Mutex`] trait for each shared resource accessible to the task.
 
 The only method on this trait, [`lock`], runs its closure argument in a critical section.
 
@@ -91,7 +95,7 @@ $ cargo run --example late
 {{#include ../../../../ci/expected/late.run}}
 ```
 
-## Only shared access
+## Only shared (`&-`) access
 
 By default the framework assumes that all tasks require exclusive access (`&mut-`) to resources but it is possible to specify that a task only requires shared access (`&-`) to a resource using the `&resource_name` syntax in the `resources` list.
 
@@ -121,4 +125,3 @@ There exists two other options dealing with resources
   this is safe.
 * `#[task_local]`: there must be only one task using this resource,
   similar to a `static mut` task local resource, but (optionally) set-up by init.
-

examples/resource.rs

@@ -13,55 +13,68 @@ mod app {
     use lm3s6965::Interrupt;
 
     #[shared]
-    struct Shared {
+    struct Shared {}
-        shared: u32,
-    }
 
     #[local]
-    struct Local {}
+    struct Local {
+        local_to_uart0: i64,
+        local_to_uart1: i64,
+    }
 
     #[init]
     fn init(_: init::Context) -> (Shared, Local, init::Monotonics) {
         rtic::pend(Interrupt::UART0);
         rtic::pend(Interrupt::UART1);
 
-        (Shared { shared: 0 }, Local {}, init::Monotonics())
+        (
+            Shared {},
+            Local {
+                local_to_uart0: 0,
+                local_to_uart1: 0,
+            },
+            init::Monotonics(),
+        )
     }
 
-    // `shared` cannot be accessed from this context
+    // `#[local]` resources cannot be accessed from this context
     #[idle]
     fn idle(_cx: idle::Context) -> ! {
         debug::exit(debug::EXIT_SUCCESS);
 
-        // error: no `shared` field in `idle::Context`
+        // error: no `local` field in `idle::Context`
-        // _cx.shared.shared += 1;
+        // _cx.local.local_to_uart0 += 1;
+
+        // error: no `local` field in `idle::Context`
+        // _cx.local.local_to_uart1 += 1;
 
         loop {
             cortex_m::asm::nop();
         }
     }
 
-    // `shared` can be accessed from this context
+    // `local_to_uart0` can only be accessed from this context
     // defaults to priority 1
-    #[task(binds = UART0, shared = [shared])]
+    #[task(binds = UART0, local = [local_to_uart0])]
-    fn uart0(mut cx: uart0::Context) {
+    fn uart0(cx: uart0::Context) {
-        let shared = cx.shared.shared.lock(|shared| {
+        *cx.local.local_to_uart0 += 1;
-            *shared += 1;
+        let local_to_uart0 = cx.local.local_to_uart0;
-            *shared
-        });
 
-        hprintln!("UART0: shared = {}", shared).unwrap();
+        // error: no `local_to_uart1` field in `uart0::LocalResources`
+        cx.local.local_to_uart1 += 1;
+
+        hprintln!("UART0: local_to_uart0 = {}", local_to_uart0).unwrap();
     }
 
-    // `shared` can be accessed from this context
+    // `shared` can only be accessed from this context
     // explicitly set to priority 2
-    #[task(binds = UART1, shared = [shared], priority = 2)]
+    #[task(binds = UART1, local = [local_to_uart1], priority = 2)]
-    fn uart1(mut cx: uart1::Context) {
+    fn uart1(cx: uart1::Context) {
-        let shared = cx.shared.shared.lock(|shared| {
+        *cx.local.local_to_uart1 += 1;
-            *shared += 1;
+        let local_to_uart1 = cx.local.local_to_uart1;
-            *shared
-        });
 
-        hprintln!("UART1: shared = {}", shared).unwrap();
+        // error: no `local_to_uart0` field in `uart1::LocalResources`
+        // cx.local.local_to_uart0 += 1;
+
+        hprintln!("UART1: local_to_uart1 = {}", local_to_uart1).unwrap();
     }
 }