Process Management

Process Management

Preemptive weighted round-robin scheduler. Fixed process table (64 entries).

See also: Architecture, Syscalls, Userspace, SMP, Memory Management, Shell

Process states

PROC_RUN → PROC_BLOCKED → PROC_ZOMBIE → PROC_EMPTY

Scheduler

• Each process has sched_weight (1–64) and sched_quantum countdown
• PIT fires at 1000 Hz; ticks decrement quantum, switch when quantum hits 0
• Compositor gets weight 4 for responsive GUI
• nice/renice set job weights from the Shell

Kernel threads

Created via create_task(func, stack). Run in ring 0 with kernel PML4.

User processes

Ring 3 with own PML4. Lifecycle: spawn → schedule → exit → reap. See Userspace.

Blocking

• kwait(pid): block until child exits
• sleep(ms): block with wake_tick, scheduler wakes on timer tick
• cli;hlt yield pattern ensures atomic check-then-sleep

Preemption safety

preempt_disable/enable guards kmalloc, kfree, EXT2 ops, VFS node pool.

SMP

See SMP for multi-core scheduling (future: per-CPU run queues).