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c80b7bf3b2
docs/plan/init.md milestones I0 and I1.
**The split.** schinit is PID 1 and does four things: bootstrap the
filesystems, fork schinitd, fork jobs on schinitd's behalf, reap children. No
manifest parsing, no filesystem walking after boot, no allocation. It is the
one program on the machine with no supervisor, so it is written to be too
boring to fail.
schinitd is PID 2 and holds everything else -- /etc/schinit, respawn policy,
throttling -- and is restartable, which is where the bugs are allowed to be.
**Jobs are forked by PID 1, not by schinitd.** That is the load-bearing
detail. schinitd decides and asks; PID 1 acts. So every job is a child of PID
1 at all times, and a supervisor that dies orphans nothing, reparents nothing
and restarts nothing.
**/proc/schinit** is the job table, written by PID 1 whenever it changes. The
kernel holds the text and does not interpret it: a procfs generator runs in
the kernel, and walking PID 1's memory to answer a read would put a userspace
program's format into the kernel, where it would rot.
Verified the way the plan asks for -- `kill 3`, then look:
schinitd: adopting os.schos.console-shell
schinitd: adopting os.schos.tty2-shell
/proc/schinit byte-identical across the restart, same pids, same cookies, same
start times, and the shell being typed into never noticed.
The first attempt got I1 wrong in the instructive way: PID 1 published the
table and schinitd never read it back, so the restarted supervisor started
everything a second time -- two console shells on one terminal, which is the
split-brain this plan rejects the two-init scheme for, reached by a different
road. Publishing state is half of it; coming back and believing it is the
other half.
The protocol is include/schinit.h: fixed-size messages, versioned in the
hello, entirely internal. Fixed-size so PID 1 never allocates, and a
supervisor that has gone mad cannot make it run a parser.
Still to come: I2 (heartbeat both ways, so a hang is as detectable as a death)
and I3 (proc_reincarnate, the actual law change).
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
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| .. | ||
| 1.0.md | ||
| foundations.md | ||
| hybrid.md | ||
| init.md | ||
| README.md | ||
| roadmap.md | ||
| schapi.md | ||
| wayland.md | ||
What happens next
Everything in this directory is unbuilt. When a piece of it is finished it leaves — deleted from here, rewritten as a description in ../architecture/. See the rule.
Read 1.0.md first.
It draws a finish line and puts most of the work below on the far side of it. Anything not named there is not being worked on, and the documents in this directory describe more than 1.0 contains.
The three current decisions
Taken together, because they turn out to need the same foundation.
| wayland.md | The GUI stack becomes Wayland. SchWM and SchDE are deleted; Schcom survives and changes its wire format. |
| hybrid.md | The kernel becomes hybrid — drivers move out into userspace processes, starting with the GPU. |
| init.md | PID 1 stops being a process and becomes a role the kernel guarantees is filled. |
And the one they all wait on:
| foundations.md | Descriptor passing, shared memory, sockets in the filesystem. The critical path. |
And the one that says which parts of the above are actually being worked on:
| 1.0.md | The finish line. Four gates, and everything else explicitly deferred. |
Two longer-horizon documents sit behind these: schapi.md, the API layering and the compatibility promise, and roadmap.md, which holds everything still open that is not one of the three above.
The order
Set by 1.0.md, which is the authority. In short:
0. Fix what is already wrong — first
Not a document of its own; it is Gate 0 of 1.0.md, assembled from the What it does not do sections in ../architecture/.
Before any new capability, and the reason is the one that put
netdev_selftest() before the TCP/IP stack: a compositor built on a kernel with
an unexplained hang and a socket layer that reports success for things it did not
do will fail in ways indistinguishable from its own bugs.
1. foundations.md — the critical path
Both the Wayland work and the hybrid work stop here. Descriptor passing and shared memory are the substrate for handing a buffer to a compositor and for handing a device to a driver process. Doing it once for both is the entire reason these are one plan rather than three.
2. init.md — before the desktop, not after
A compositor being brought up for the first time crashes constantly, and something that restarts it and says why is worth far more during that work than at the end of it.
3. wayland.md — with the GPU driver still in the kernel
W1–W3 and a terminal. W4 and W5 are post-1.0.
4. hybrid.md — after 1.0
Deliberately last: designing a userspace driver interface with no driver consuming it produces an interface that is wrong in ways nobody can see. The compositor is the demanding consumer that makes the interface judgeable, so it has to exist first.
In one sentence
Fix what is broken, build the descriptor-passing and shared-memory substrate, make init survivable, put a terminal on the screen — and only then use the compositor as the pressure that shapes the userspace driver interface.
What this plan does not address
Stated here so it is not mistaken for covered:
- No IOMMU, so the hybrid work isolates against bugs and not against a hostile driver.
- No page cache, so
foundations.mddelivers amemfdand not a general answer to shared file mappings. The general answer is still owed. - No dynamic linking, so no Mesa, no accelerated clients, and no third party
shipping a
.sofor anything. - A new compatibility surface between PID 1 and PID 2, created by a plan whose own schapi.md §3 spends a section warning about those.
- The three open networking items —
getsockname, routing, and interrupt-driven receive — are untouched by any of this and still open. They are in roadmap.md.