Refactor the scheduler so all scheduleable work is wrapped in Arc<Work>,
replacing the previous per-CPU wait_q design where sleeping tasks were
bound to a specific CPU. Wakers now hold direct Arc<Work> references and
can re-enqueue tasks on any CPU upon wakeup.
Key changes:
- Add Work struct wrapping OwnedTask with an AtomicTaskState and
scheduler metadata (SchedulerData), replacing the old SchedulableTask.
Remove Task::state (Arc<SpinLock<TaskState>>). Work::state is now the
single source of truth for task state.
- Rewrite the run queue using BinaryHeap-based eligible/ineligible split
(EEVDF) with a dedicated VClock, replacing the BTreeMap linear scan.
Extract vclock into its own module.
- Rewrite wakers to hold Arc<Work> directly instead of looking up tasks
by TaskDescriptor from TASK_LIST.
- Replace lock-based sleep transitions in uspc_ret with atomic CAS
(try_sleep_current) that correctly detects concurrent Woken state.
- Simplify least-tasked-CPU metric to use only run-queue weight, since
sleeping tasks are no longer bound to any CPU.
- Add current_work() accessor.
This commit refactors the signal handling subsystem to address a bug in
process creation and to improve the separation of concerns between
signal delivery and signal disposition.
1. Fix Action Table Sharing:
Previously, the signal action table was wrapped in an `Arc`, causing
forked child processes to inadvertently share signal dispositions with
the parent. `SignalActionState` now contains a direct `SigActionSet` and
implements Clone, ensuring that processes receive a private copy of the
action table upon fork/clone.
2. Decouple Signal Selection from Execution:
The logic for selecting a pending signal has been moved from the
disposition state into a new `take_signal` method on `OwnedTask`. This
decouples the "taking" of a signal (respecting masks and priorities)
from the "actioning" of that signal. This is a prerequisite for
implementing ptrace.
3. Various cleanup bits:
- Renamed `SignalState` to `SignalActionState` to more accurately
reflect that it manages signal dispositions.
- Removed the `pending` signal set out of the action state and directly
into the `ThreadGroup` and `OwnedTask`.
- Renamed `set_pending` to `set_signal` for consistency.
- Simplified the signal delivery loop in `dispatch_userspace_task`
using the new `take_signal` API.
Currently, each task implements it's own priority value. In Linux, each
thread group (process) has a default process which all tasks in that
group inherit. Tasks can, however, override the default process
priority.
Implement that logic here which also fixes the current compilation error
on master.
