Merge #469

469: Goodbye static mut r=AfoHT a=korken89

Squashed and updated version of @perlindgren branch.

In release there are 0 bytes difference for all examples :tada: 
For debug we see a bloat of ~1-2% worst case, commonly less.

Complete diff of sizes for all examples (first is goodbye static mut, second is master):

```

<   27220	      0	     28	  27248	   6a70	spawn
---
>   27092	      0	     28	  27120	   69f0	spawn

<   16916	      0	     44	  16960	   4240	late
---
>   16836	      0	     44	  16880	   41f0	late

<   15952	      0	     12	  15964	   3e5c	type-usage
---
>   15872	      0	     12	  15884	   3e0c	type-usage

<   22068	      0	     44	  22112	   5660	cfg
---
>   21812	      0	     44	  21856	   5560	cfg

<   34784	      0	     40	  34824	   8808	periodic
---
>   34496	      0	     40	  34536	   86e8	periodic

<   22308	      0	     32	  22340	   5744	task
---
>   21972	      0	     32	  22004	   55f4	task

<   15076	      8	     24	  15108	   3b04	task-local
---
>   14980	      8	     24	  15012	   3aa4	task-local

<   12884	      0	     24	  12908	   326c	destructure
---
>   12820	      0	     24	  12844	   322c	destructure

<   10128	      0	     16	  10144	   27a0	init
---
>   10112	      0	     16	  10128	   2790	init

<   19044	      0	     20	  19064	   4a78	task_named_main
---
>   18916	      0	     20	  18936	   49f8	task_named_main

<   27252	      0	     28	  27280	   6a90	extern_spawn
---
>   27124	      0	     28	  27152	   6a10	extern_spawn

<   10176	      0	     16	  10192	   27d0	idle
---
>   10160	      0	     16	  10176	   27c0	idle

<   13972	      0	     16	  13988	   36a4	resource
---
>   13940	      0	     16	  13956	   3684	resource

<   16228	      0	     24	  16252	   3f7c	multilock
---
>   16116	      0	     24	  16140	   3f0c	multilock

<   14660	      0	     16	  14676	   3954	lock
---
>   14628	      0	     16	  14644	   3934	lock

<   10416	      0	     16	  10432	   28c0	task-local-minimal
---
>   10400	      0	     16	  10416	   28b0	task-local-minimal

<   14164	      0	     24	  14188	   376c	generics
---
>   14148	      0	     24	  14172	   375c	generics

<   30644	      0	     48	  30692	   77e4	message
---
>   30308	      0	     48	  30356	   7694	message

<   28964	      0	     36	  29000	   7148	spawn2
---
>   28724	      0	     36	  28760	   7058	spawn2

<   15952	      0	      8	  15960	   3e58	t-schedule-core-stable
---
>   15872	      0	      8	  15880	   3e08	t-schedule-core-stable

<   17408	      0	     20	  17428	   4414	t-cfg
---
>   17248	      0	     20	  17268	   4374	t-cfg

<   12948	      0	     16	  12964	   32a4	hardware
---
>   12932	      0	     16	  12948	   3294	hardware

<   54640	      0	    104	  54744	   d5d8	t-schedule
---
>   53696	      0	    104	  53800	   d228	t-schedule

<   26132	      0	    548	  26680	   6838	pool
---
>   25876	      0	    548	  26424	   6738	pool

<   22372	      0	     56	  22428	   579c	cfg-whole-task
---
>   22100	      0	     56	  22156	   568c	cfg-whole-task

<   38292	      0	     76	  38368	   95e0	schedule
---
>   37828	      0	     76	  37904	   9410	schedule

<   21216	      0	     32	  21248	   5300	t-spawn
---
>   20880	      0	     32	  20912	   51b0	t-spawn

<   22820	      0	     56	  22876	   595c	capacity
---
>   22580	      0	     56	  22636	   586c	capacity

<   17060	      0	     48	  17108	   42d4	static
---
>   16980	      0	     48	  17028	   4284	static

<   20288	      0	     24	  20312	   4f58	ramfunc
---
>   20096	      0	     24	  20120	   4e98	ramfunc

<   11760	      0	     20	  11780	   2e04	t-resource
---
>   11664	      0	     20	  11684	   2da4	t-resource

<   13028	      0	     16	  13044	   32f4	only-shared-access
---
>   13012	      0	     16	  13028	   32e4	only-shared-access

<   16576	      0	     16	  16592	   40d0	not-sync
---
>   16432	      0	     16	  16448	   4040	not-sync

<   13892	      0	     16	  13908	   3654	resource-user-struct
---
>   13860	      0	     16	  13876	   3634	resource-user-struct

<   37472	      0	     64	  37536	   92a0	double_schedule
---
>   36960	      0	     64	  37024	   90a0	double_schedule

<   17648	      0	      8	  17656	   44f8	t-stask-main
---
>   17520	      0	      8	  17528	   4478	t-stask-main

<    8816	      0	      4	   8820	   2274	t-late-not-send
---
>    8800	      0	      4	   8804	   2264	t-late-not-send

<   23280	      0	     32	  23312	   5b10	types
---
>   23120	      0	     32	  23152	   5a70	types
```

Co-authored-by: Emil Fresk <emil.fresk@gmail.com>

1 files changed, 13 insertions, 8 deletions

diff --git a/macros/src/codegen/timer_queue.rs b/macros/src/codegen/timer_queue.rs
index 0d2c51ea..14e91054 100644
--- a/macros/src/codegen/timer_queue.rs
+++ b/macros/src/codegen/timer_queue.rs
@@ -15,7 +15,7 @@ pub fn codegen(app: &App, analysis: &Analysis, _extra: &Extra) -> Vec<TokenStrea
             // #[doc = #doc]
             #[doc(hidden)]
             #[allow(non_camel_case_types)]
-            static mut #tq_marker: u32 = 0;
+            static #tq_marker: rtic::RacyCell<u32> = rtic::RacyCell::new(0);
         ));
 
         let t = util::schedule_t_ident();
@@ -35,6 +35,7 @@ pub fn codegen(app: &App, analysis: &Analysis, _extra: &Extra) -> Vec<TokenStrea
                 })
                 .collect::<Vec<_>>();
 
+            // For future use
             // let doc = "Tasks that can be scheduled".to_string();
             items.push(quote!(
                 // #[doc = #doc]
@@ -61,6 +62,7 @@ pub fn codegen(app: &App, analysis: &Analysis, _extra: &Extra) -> Vec<TokenStrea
 
         // Static variables and resource proxy
         {
+            // For future use
             // let doc = &format!("Timer queue for {}", monotonic_name);
             let cap = app
                 .software_tasks
@@ -71,18 +73,22 @@ pub fn codegen(app: &App, analysis: &Analysis, _extra: &Extra) -> Vec<TokenStrea
             let tq_ty =
                 quote!(core::mem::MaybeUninit<rtic::export::TimerQueue<#mono_type, #t, #n>>);
 
+            // For future use
+            // let doc = format!(" RTIC internal: {}:{}", file!(), line!());
             items.push(quote!(
                 #[doc(hidden)]
-                static mut #tq: #tq_ty = core::mem::MaybeUninit::uninit();
+                static #tq: rtic::RacyCell<#tq_ty> =
+                    rtic::RacyCell::new(core::mem::MaybeUninit::uninit());
             ));
 
             let mono = util::monotonic_ident(&monotonic_name);
             let mono = util::mark_internal_ident(&mono);
+            // For future use
             // let doc = &format!("Storage for {}", monotonic_name);
 
             items.push(quote!(
                 #[doc(hidden)]
-                static mut #mono: Option<#mono_type> = None;
+                static #mono: rtic::RacyCell<Option<#mono_type>> = rtic::RacyCell::new(None);
             ));
         }
 
@@ -113,7 +119,7 @@ pub fn codegen(app: &App, analysis: &Analysis, _extra: &Extra) -> Vec<TokenStrea
                     quote!(
                         #(#cfgs)*
                         #t::#name => {
-                            rtic::export::interrupt::free(|_| #rq.split().0.enqueue_unchecked((#rqt::#name, index)));
+                            rtic::export::interrupt::free(|_| #rq.get_mut_unchecked().split().0.enqueue_unchecked((#rqt::#name, index)));
 
                             #pend
                         }
@@ -132,10 +138,9 @@ pub fn codegen(app: &App, analysis: &Analysis, _extra: &Extra) -> Vec<TokenStrea
                 #[no_mangle]
                 #[allow(non_snake_case)]
                 unsafe fn #bound_interrupt() {
-
                     while let Some((task, index)) = rtic::export::interrupt::free(|_|
-                        if let Some(mono) = #app_path::#m_ident.as_mut() {
-                            (&mut *#tq.as_mut_ptr()).dequeue(|| #disable_isr, mono)
+                        if let Some(mono) = #app_path::#m_ident.get_mut_unchecked().as_mut() {
+                            (&mut *#tq.get_mut_unchecked().as_mut_ptr()).dequeue(|| #disable_isr, mono)
                         } else {
                             // We can only use the timer queue if `init` has returned, and it
                             // writes the `Some(monotonic)` we are accessing here.
@@ -147,7 +152,7 @@ pub fn codegen(app: &App, analysis: &Analysis, _extra: &Extra) -> Vec<TokenStrea
                         }
                     }
 
-                    rtic::export::interrupt::free(|_| if let Some(mono) = #app_path::#m_ident.as_mut() {
+                    rtic::export::interrupt::free(|_| if let Some(mono) = #app_path::#m_ident.get_mut_unchecked().as_mut() {
                         mono.on_interrupt();
                     });
                 }