Module deferred_work 

Deferred work queue — softirq-equivalent for Strat9-OS.

Moves heavy tick processing out of the hardirq handler into safe execution contexts (post-switch, idle loop, syscall return).

Design

Each CPU has a lock-free AtomicU32 bitmask of pending work items. The hardirq timer handler calls raise_deferred_work() which sets bits atomically — no locks, no allocation, O(1) cost.

Processing happens at safe points where IRQs may be re-enabled and scheduler locks can be acquired without deadlock:

• finish_switch() — after cooperative context switch completes
• finish_interrupt_switch() — after interrupt-driven switch completes
• idle_task_main() — idle loop before HLT
• maybe_preempt() — at preemption entry (for work raised during IRQ)

What stays in hardirq

• TICK_COUNT, CPU_TOTAL_TICKS, CPU_LOCAL_TICKS increments (lock-free)
• FORCE_RESCHED_HINT setting (lock-free)
• speaker_tick, n3_watchdog_tick (minimal)
• EOI (must be immediate)

What moves to deferred

• tick_all_timers() — interval timer processing
• check_wake_deadlines() — deadline-based wakeups
• Per-task Fair class accounting (runnable_len, tick_update_wait)

Structs

DeferredWorkCpu 🔒

Per-CPU deferred work state.

DeferredWorkMetrics

Snapshot of deferred work metrics across all CPUs.

Enums

DeferredWork

Work item types that can be deferred from hardirq context.

Statics

DEFERRED_WORK 🔒

Per-CPU deferred work queues.

Functions

has_pending

Check if there is pending deferred work on the current CPU.

metrics_snapshot

Take a snapshot of deferred work metrics.

process_deferred_work

Process deferred work items for the current CPU.

process_per_task_accounting 🔒

Process per-task Fair class accounting for the current CPU.

raise_deferred_work

Raise deferred work items for the current CPU.

raise_tick_deferred_work

Raise all tick-related deferred work items for the current CPU.

reset_metrics

Reset deferred work metrics.