Merge #390

390: Spawn and schedule from anywhere r=AfoHT a=korken89

This PR moves RTIC to the spawn and schedule from anywhere syntax.

Notable changes:
 * We do no longer support non-`Send` types.
 * Some extra code is generated as any task may spawn/schedule any task. However Rust/LLVM does a great job optimizing away non used instantiations (no real code-size difference observed).
 * Worst case priority inversion has increased, but it is now predictable.

Upsides:
 * With this we should be able to support async/await.
 * RTIC tasks can now be callbacks (spawned and scheduled).
 * RTIC tasks can be stored.

Needs the following PR to land first: https://github.com/rtic-rs/rtic-syntax/pull/34

The following now works:

```rust
#[rtic::app(device = lm3s6965, monotonic = rtic::cyccnt::CYCCNT)]
mod app {
    #[init]
    fn init(mut cx: init::Context) -> init::LateResources {
        // Init stuff...

        // New spawn syntax
        foo::spawn().unwrap();

        // New schedule syntax
        bar::schedule(now + 4_000_000.cycles()).unwrap();

        init::LateResources {}
    }

    #[task]
    fn foo(_: foo::Context) {}

    #[task]
    fn bar(_: bar::Context) {}

    extern "C" {
        fn SSI0();
    }
}

```

Co-authored-by: Per Lindgren <per.lindgren@ltu.se>
Co-authored-by: Emil Fresk <emil.fresk@gmail.com>

1 files changed, 3 insertions, 7 deletions

diff --git a/macros/src/codegen/pre_init.rs b/macros/src/codegen/pre_init.rs
index 2aaf9ebd..17c9c2f4 100644
--- a/macros/src/codegen/pre_init.rs
+++ b/macros/src/codegen/pre_init.rs
@@ -12,12 +12,8 @@ pub fn codegen(app: &App, analysis: &Analysis, extra: &Extra) -> Vec<TokenStream
     stmts.push(quote!(rtic::export::interrupt::disable();));
 
     // Populate the FreeQueue
-    for fq in &analysis.free_queues {
-        // Get the task name
-        let name = fq.0;
-        let task = &app.software_tasks[name];
+    for (name, task) in &app.software_tasks {
         let cap = task.args.capacity;
-
         let fq_ident = util::fq_ident(name);
 
         stmts.push(quote!(
@@ -81,8 +77,8 @@ pub fn codegen(app: &App, analysis: &Analysis, extra: &Extra) -> Vec<TokenStream
     }
 
     // Initialize the SysTick if there exist a TimerQueue
-    if let Some(tq) = analysis.timer_queues.first() {
-        let priority = tq.priority;
+    if extra.monotonic.is_some() {
+        let priority = analysis.channels.keys().max().unwrap();
 
         // Compile time assert that this priority is supported by the device
         stmts.push(quote!(let _ = [(); ((1 << #nvic_prio_bits) - #priority as usize)];));