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docs: catch the build docs up with the package split

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Review findings: the plan doc claimed no implementation existed, had the
domain dependency order wrong (kernel depends on protocol; device on
kernel + protocol + csv), never placed the three shared contracts, and
named a nonexistent new-driver-checklist.md. Its status now records the
implemented phases (and the deliberate pci-bus-first pilot), the target
shape carries the contract placements and the path-dependency-only
constraint on the kernel package's out-of-root abi export, and the
execution notes describe the post-pilot build for whichever session
runs the remaining waves. README's repo layout gains build-support/
and the packages-note; driver-model, threading, system-requirements,
and the two display plan docs stop citing root build.zig for recipe
facts that now live in build-support.
This commit is contained in:
Daniel Samson
2026-07-26 23:12:14 +01:00
parent 15575960bd
commit 902e4a0a9e
8 changed files with 101 additions and 56 deletions
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docs/os-development/threading.md
+8 -6
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@@ -61,9 +61,10 @@ runtime — rebuilt in lockstep — knows the mapping.
backend would either bake danos syscall numbers into std (breaking ABI privacy and
renumbering) or fork std to route back through the runtime — a permanent rebase
cost that buys nothing the native type doesn't.
2. **Our user binaries are built `single_threaded = true`** ([build.zig](../../build.zig)
`addUserBinary`), which compiles threading out entirely and makes atomics and TLS
single-threaded. Threads need this flipped per binary regardless.
2. **Our user binaries are built `single_threaded = true`** (the shared recipe in
[build-support/build.zig](../../build-support/build.zig)), which compiles threading
out entirely and makes atomics and TLS single-threaded. Threads need this flipped
per binary regardless.
So we take the *shape* of `std.Thread`, not the *type*. The cost of replicating the
surface (spawn/join/Mutex/Condition) is small; the cost of the std type is the ABI
@@ -236,9 +237,10 @@ see the intro). Two scoped pieces, as built:
### Build: multi-threaded codegen, opt-in
A binary opts in by being added with `addThreadedUserBinary` — as `addUserBinary`,
but the shared implementation builds it `single_threaded = false` — so atomics and
(later) TLS are real. Threads and atomics are unsound in a `single_threaded` image,
A binary opts in with `addThreadedUserBinary` in the root `build.zig` (or
`.threaded = true` in a binary package's `build_support.userBinary` call) — the
shared recipe in build-support then builds it `single_threaded = false` — so atomics
and (later) TLS are real. Threads and atomics are unsound in a `single_threaded` image,
so a binary must opt in **before** it may call `Thread.spawn`. Everyone else
stays single-threaded and lean.