Bug: process PID table is not populated

[pbalduino]

Summary

The process table lookup path exists, but newly created processes are not consistently inserted into procs[]. PID-based management can therefore fail to find live tasks.

This affects routines such as proc_find_by_pid, proc_kill_pid, wait/kill/list behavior, and procfs-style process reporting.

Current Notes

Tracked locally in scheduler_issues.md as "PID Table Never Populated".

Relevant code:

• src/kernel/proc/proc.c: procs[]
• src/kernel/proc/proc.c: proc_find_by_pid
• src/kernel/proc/proc.c: proc_kill_pid
• process creation/exec and teardown paths

Expected Behavior

Every live process with a PID should be discoverable through the canonical PID table, and removed from that table exactly once during teardown.

Proposed Fix

Assign each allocated process to a free slot in procs[] during creation/exec, and clear that slot during teardown after no PID lookup should return it.

The implementation should define ownership clearly so that fork/exec/wait/kill/procfs all agree on process lifetime.

Dependencies

• Issue Implement fork/exec process creation system #93: Fork/exec process creation (CLOSED)
• Issue Implement UNIX signals for process control and communication #103: UNIX signals for process control and communication (CLOSED)
• Issue Implement /proc filesystem (procfs) #244: Implement /proc filesystem (CLOSED)

Blocks

• Issue Improved ps command to match Linux behavior #283: Improved ps command to match Linux behavior
• Issue Bug: scheduler process cleanup leaks resources #427: Scheduler process cleanup leaks resources

Related Issues

• Issue Bug: ready queue updates are not atomic #425: Ready queue updates are not atomic
• Issue Design formal per-process virtual memory layout system #55: Design formal per-process virtual memory layout system
• Issue Implement thread-aware system calls and kernel integration #113: Thread-aware system calls and kernel integration

Validation

• Add or update tests for PID lookup after process creation.
• Validate kill/wait/list behavior against live and terminated processes.
• Boot smoke test with repeated fork/exec/wait workloads.
• Confirm make test still passes.