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Diffstat (limited to 'README.md')
| -rw-r--r-- | README.md | 28 |
1 files changed, 26 insertions, 2 deletions
@@ -45,13 +45,35 @@ User loads `C` = syscall number, args in `DE`/`B`, then `rst $30`. Return in `A` | # | name | status | |---|---------|--------| -| 0 | exit | ✅ marks zombie, reschedules | +| 0 | exit | ✅ zombie + reparent orphans + wake waiter | | 1 | fork | ✅ copies the 8 KiB bank, child returns 0 | | 3 | write | ✅ `DE`=buf `B`=len → serial console | | 6 | exec | ✅ `B`=program id → maps ROM text bank, jumps in | +| 7 | wait | ✅ blocks; reaps a zombie child → `A`=pid `B`=code | | 8 | getpid | ✅ | | 11| yield | ✅ cooperative switch | -| 2,4,5,7,9,10 | read/open/close/wait/kill/brk | ⛔ `ENOSYS` | +| 2,4,5,9,10 | read/open/close/kill/brk | ⛔ `ENOSYS` | + +### Process lifecycle (exit / wait / reaping) + +The classic Unix zombie/reap dance, adapted to banked memory: + +- **`exit(code)`** sets `PS_ZOMBIE` + status, **reparents** any children to init + (pid 1), **wakes** the parent if it's blocked in `wait()`, then schedules + away forever. Its resources are freed by the reaper, not here. +- **`wait()`** scans for a `PS_ZOMBIE` child. Found → **reap**: free its + cart-RAM bank (back to the allocator) and its PCB slot, return pid + code. + Children exist but none dead → set self `PS_BLOCKED` and yield, retry on wake. + No children → return `$FF` (`ECHILD`). +- The scheduler skips non-`READY` procs; `FindNextReady` returns carry when + nothing is runnable so `yield` just keeps the caller running (idle). +- **Cart-RAM banks are a free list** (`wBankUsed` bitmap): `AllocRamBank` / + `FreeRamBank`. Verified by running 6 workers through only 3 child banks + (`w2w3w4w5w6w7`) — each reaped bank is recycled by the next `fork`. + +Lifecycle demo (`tasks.asm`): init forks 3 workers, each `exec`s PROG_WORKER +(prints `w`, exits with its pid), init `wait`s and reaps all three → +`wwwR2R3R4!`. ### exec (`sys_exec`, src/proc.asm + programs.asm) @@ -131,7 +153,9 @@ A real gbos would render to VRAM; serial is the zero-VRAM debug channel. - [x] `fork`: copy parent's 8 KiB RAM bank → free bank, child returns 0 - [x] `exec`: point `PROC_ROMB` at a program in a ROM bank, reset stack, enter +- [x] `exit` / `wait` / zombie reaping + cart-RAM bank recycling (free list) - [ ] `exec` refinement: copy `.data` from ROM + zero `.bss` for RW globals +- [ ] a real shell program: `fork`+`exec`+`wait` driven from the serial console - [ ] Preemptive scheduling: real context save in `TimerISR` → `hSwitchTo` - [ ] Use the `$D000-$DFFF` u-area (SVBK) for per-process kernel state / kstack - [ ] `brk`/heap allocator inside the task bank (heap up, stack down, collision = ENOMEM) |