Merge pull request #4608 from diondokter/upstream-drs-2

[embassy-executor]: Upstream "Earliest Deadline First" Scheduler (version 2)

1 files changed, 67 insertions, 0 deletions

diff --git a/embassy-executor/src/metadata.rs b/embassy-executor/src/metadata.rs
index f92c9b37c..4220048a6 100644
--- a/embassy-executor/src/metadata.rs
+++ b/embassy-executor/src/metadata.rs
@@ -7,11 +7,15 @@ use core::task::Poll;
 use critical_section::Mutex;
 
 use crate::raw;
+#[cfg(feature = "scheduler-deadline")]
+use crate::raw::Deadline;
 
 /// Metadata associated with a task.
 pub struct Metadata {
     #[cfg(feature = "metadata-name")]
     name: Mutex<Cell<Option<&'static str>>>,
+    #[cfg(feature = "scheduler-deadline")]
+    deadline: raw::Deadline,
 }
 
 impl Metadata {
@@ -19,6 +23,10 @@ impl Metadata {
         Self {
             #[cfg(feature = "metadata-name")]
             name: Mutex::new(Cell::new(None)),
+            // NOTE: The deadline is set to zero to allow the initializer to reside in `.bss`. This
+            // will be lazily initalized in `initialize_impl`
+            #[cfg(feature = "scheduler-deadline")]
+            deadline: raw::Deadline::new_unset(),
         }
     }
 
@@ -52,4 +60,63 @@ impl Metadata {
     pub fn set_name(&self, name: &'static str) {
         critical_section::with(|cs| self.name.borrow(cs).set(Some(name)))
     }
+
+    /// Get this task's deadline.
+    #[cfg(feature = "scheduler-deadline")]
+    pub fn deadline(&self) -> u64 {
+        self.deadline.instant_ticks()
+    }
+
+    /// Set this task's deadline.
+    ///
+    /// This method does NOT check whether the deadline has already passed.
+    #[cfg(feature = "scheduler-deadline")]
+    pub fn set_deadline(&self, instant_ticks: u64) {
+        self.deadline.set(instant_ticks);
+    }
+
+    /// Remove this task's deadline.
+    /// This brings it back to the defaul where it's not scheduled ahead of other tasks.
+    #[cfg(feature = "scheduler-deadline")]
+    pub fn unset_deadline(&self) {
+        self.deadline.set(Deadline::UNSET_TICKS);
+    }
+
+    /// Set this task's deadline `duration_ticks` in the future from when
+    /// this future is polled. This deadline is saturated to the max tick value.
+    ///
+    /// Analogous to `Timer::after`.
+    #[cfg(all(feature = "scheduler-deadline", feature = "embassy-time-driver"))]
+    pub fn set_deadline_after(&self, duration_ticks: u64) {
+        let now = embassy_time_driver::now();
+
+        // Since ticks is a u64, saturating add is PROBABLY overly cautious, leave
+        // it for now, we can probably make this wrapping_add for performance
+        // reasons later.
+        let deadline = now.saturating_add(duration_ticks);
+
+        self.set_deadline(deadline);
+    }
+
+    /// Set the this task's deadline `increment_ticks` from the previous deadline.
+    ///
+    /// This deadline is saturated to the max tick value.
+    ///
+    /// Note that by default (unless otherwise set), tasks start life with the deadline
+    /// not set, which means this method will have no effect.
+    ///
+    /// Analogous to one increment of `Ticker::every().next()`.
+    ///
+    /// Returns the deadline that was set.
+    #[cfg(feature = "scheduler-deadline")]
+    pub fn increment_deadline(&self, duration_ticks: u64) {
+        let last = self.deadline();
+
+        // Since ticks is a u64, saturating add is PROBABLY overly cautious, leave
+        // it for now, we can probably make this wrapping_add for performance
+        // reasons later.
+        let deadline = last.saturating_add(duration_ticks);
+
+        self.set_deadline(deadline);
+    }
 }