feat(threads): delay thread start until init_task() has finished

src/riot-rs-embassy/src/lib.rs

@@ -154,7 +154,7 @@ mod executor_thread {
 }
 
 #[cfg(feature = "executor-thread")]
-#[riot_rs_macros::thread(autostart, stacksize = executor_thread::STACKSIZE, priority = executor_thread::PRIORITY)]
+#[riot_rs_macros::thread(autostart, no_wait, stacksize = executor_thread::STACKSIZE, priority = executor_thread::PRIORITY)]
 fn init() {
     debug!("riot-rs-embassy::init(): using thread executor");
     let p = arch::init();
@@ -326,4 +326,7 @@ async fn init_task(mut peripherals: arch::OptionalPeripherals) {
     let _ = peripherals;
 
     debug!("riot-rs-embassy::init_task() done");
+
+    #[cfg(feature = "threading")]
+    riot_rs_threads::_events::THREAD_START_EVENT.set();
 }

src/riot-rs-macros/src/thread.rs

@@ -7,6 +7,8 @@
 /// - `autostart`: (*mandatory*) autostart the thread.
 /// - `stacksize`: (*optional*) the size of the stack allocated to the thread (in bytes).
 /// - `priority`: (*optional*) the thread's priority.
+/// - `no_wait`: (*optional*) don't wait for system initialization to be finished
+///              before starting the thread.
 ///
 /// # Examples
 ///
@@ -38,7 +40,7 @@ pub fn thread(args: TokenStream, item: TokenStream) -> TokenStream {
     #[allow(clippy::wildcard_imports)]
     use thread::*;
 
-    use quote::quote;
+    use quote::{format_ident, quote};
 
     use crate::utils::find_crate;
 
@@ -53,32 +55,45 @@ pub fn thread(args: TokenStream, item: TokenStream) -> TokenStream {
 
     let thread_function = syn::parse_macro_input!(item as syn::ItemFn);
 
+    let thread_crate = {
+        match (find_crate("riot-rs"), find_crate("riot-rs-threads")) {
+            (Some(riot_rs), _) => quote! { #riot_rs::thread },
+            (None, Some(riot_rs_threads)) => quote! { #riot_rs_threads },
+            _ => panic!(r#"neither "riot-rs" nor "riot-rs-threads" found in dependencies!"#),
+        }
+    };
+
     let no_mangle_attr = if attrs.no_mangle {
         quote! {#[no_mangle]}
     } else {
         quote! {}
     };
 
+    let maybe_wait_for_start_event = if attrs.no_wait {
+        quote! {}
+    } else {
+        quote! {#thread_crate::_events::THREAD_START_EVENT.wait();}
+    };
+
     let fn_name = thread_function.sig.ident.clone();
+    let trampoline_function_name = format_ident!("__{fn_name}_trampoline");
+
     let Parameters {
         stack_size,
         priority,
         affinity,
     } = Parameters::from(attrs);
 
-    let thread_crate = {
-        match (find_crate("riot-rs"), find_crate("riot-rs-threads")) {
-            (Some(riot_rs), _) => quote! { #riot_rs::thread },
-            (None, Some(riot_rs_threads)) => quote! { #riot_rs_threads },
-            _ => panic!(r#"neither "riot-rs" nor "riot-rs-threads" found in dependencies!"#),
-        }
-    };
-
     let expanded = quote! {
         #no_mangle_attr
         #thread_function
 
-        #thread_crate::autostart_thread!(#fn_name, stacksize = #stack_size, priority = #priority, affinity = #affinity);
+        fn #trampoline_function_name() {
+            #maybe_wait_for_start_event;
+            #fn_name()
+        }
+
+        #thread_crate::autostart_thread!(#trampoline_function_name, stacksize = #stack_size, priority = #priority, affinity = #affinity);
     };
 
     TokenStream::from(expanded)
@@ -95,9 +110,9 @@ mod thread {
         fn default() -> Self {
             // TODO: proper values
             Self {
-                stack_size: syn::parse_quote!{ 2048 },
-                priority: syn::parse_quote!{ 1 },
-                affinity: syn::parse_quote!{ None }
+                stack_size: syn::parse_quote! { 2048 },
+                priority: syn::parse_quote! { 1 },
+                affinity: syn::parse_quote! { None },
             }
         }
     }
@@ -108,12 +123,15 @@ mod thread {
 
             let stack_size = attrs.stack_size.unwrap_or(default.stack_size);
             let priority = attrs.priority.unwrap_or(default.priority);
-            let affinity = attrs.affinity.map(|expr| syn::parse_quote!{ Some(#expr) }).unwrap_or(default.affinity);
+            let affinity = attrs
+                .affinity
+                .map(|expr| syn::parse_quote! { Some(#expr) })
+                .unwrap_or(default.affinity);
 
             Self {
                 stack_size,
                 priority,
-                affinity
+                affinity,
             }
         }
     }
@@ -125,6 +143,7 @@ mod thread {
         pub priority: Option<syn::Expr>,
         pub affinity: Option<syn::Expr>,
         pub no_mangle: bool,
+        pub no_wait: bool,
     }
 
     impl Attributes {
@@ -159,6 +178,11 @@ mod thread {
                 return Ok(());
             }
 
+            if meta.path.is_ident("no_wait") {
+                self.no_wait = true;
+                return Ok(());
+            }
+
             Err(meta.error("unsupported parameter"))
         }
     }

src/riot-rs-threads/src/lib.rs

@@ -49,6 +49,13 @@ pub mod macro_reexports {
     pub use static_cell;
 }
 
+#[doc(hidden)]
+pub mod _events {
+    use crate::sync::Event;
+    // this is set in `riot_rs_embassy::init_task()``
+    pub static THREAD_START_EVENT: Event = Event::new();
+}
+
 pub use riot_rs_runqueue::{RunqueueId, ThreadId};
 pub use thread_flags as flags;