refactor(adapter): split trap/page_table/smp/entry by concern; trim comments

crates/adapter-riscv/src/smp/hints.rs

@@ -0,0 +1,42 @@
+//! State published under the kernel lock for lock-free fast paths to read.
+
+use core::sync::atomic::{AtomicUsize, Ordering};
+
+use super::{MAX_HARTS, hart_id};
+
+/// Per core: highest waiting priority + 1, 0 if its queue is empty.
+static WAITING: [AtomicUsize; MAX_HARTS] = [const { AtomicUsize::new(0) }; MAX_HARTS];
+/// Per hart: the running thread's process id + 1 and priority + 1.
+static RUNNING_PID: [AtomicUsize; MAX_HARTS] = [const { AtomicUsize::new(0) }; MAX_HARTS];
+static RUNNING_PRIORITY: [AtomicUsize; MAX_HARTS] = [const { AtomicUsize::new(0) }; MAX_HARTS];
+
+pub fn publish_waiting(core: usize, highest: Option<u8>) {
+    if let Some(w) = WAITING.get(core) {
+        w.store(highest.map_or(0, |p| p as usize + 1), Ordering::Release);
+    }
+}
+
+pub fn publish_running(pid: Option<u16>, priority: Option<u8>) {
+    let me = hart_id();
+    if let (Some(p), Some(q)) = (RUNNING_PID.get(me), RUNNING_PRIORITY.get(me)) {
+        p.store(pid.map_or(0, |x| x as usize + 1), Ordering::Release);
+        q.store(priority.map_or(0, |x| x as usize + 1), Ordering::Release);
+    }
+}
+
+/// The process the thread running on this hart belongs to.
+pub fn running_pid() -> Option<usize> {
+    let v = RUNNING_PID.get(hart_id())?.load(Ordering::Acquire);
+    v.checked_sub(1)
+}
+
+/// Whether a Yield by the running thread would change nothing: no thread
+/// waits on this core at its priority or above.
+pub fn yield_is_noop() -> bool {
+    let me = hart_id();
+    let (Some(w), Some(p)) = (WAITING.get(me), RUNNING_PRIORITY.get(me)) else {
+        return false;
+    };
+    let mine = p.load(Ordering::Acquire);
+    mine != 0 && w.load(Ordering::Acquire) < mine
+}