feat(kernel): WatchDeath + SetTimer events as notification signals; adapter wakes at earliest deadline

crates/platform/src/lib.rs

@@ -4,7 +4,7 @@ use types::{
     address::{EntryPoint, PhysicalAddress, StackPointer, VirtualAddress},
     id::{CoreId, IrqId, ProcessId},
     mapping::PagePerms,
-    time::{Ticks, TimerDuration},
+    time::Ticks,
 };
 
 /// Supplies frames for page tables while the platform builds an address
@@ -54,7 +54,9 @@ pub trait Platform {
     fn zero_frame(&mut self, pa: PhysicalAddress);
 
     fn enable_user_mode(&mut self, entry: EntryPoint, stack: StackPointer) -> !;
-    fn set_timer(&mut self, duration: TimerDuration);
+    /// Makes sure this core takes a timer interrupt by `deadline`, on top
+    /// of its scheduling tick.
+    fn wake_at(&mut self, deadline: Ticks);
     fn current_ticks(&self) -> Ticks;
     fn mask_irq(&mut self, irq: IrqId);
     fn unmask_irq(&mut self, irq: IrqId);