Time is a kernel concern in danos: the kernel owns the scheduling timer and
already exposes monotonic time via the clock/sleep/timer_bind syscalls, so a
userspace time service would be a redundant, slower path. This adds the generic
runtime.time module over those syscalls, retires the two demonstration drivers,
reorganizes the milestone docs, and makes the monotonic clock correct on Intel,
AMD, and inside any VM.
runtime.time (library/runtime/time.zig)
- Instant/Duration interface: now, sleep, spin, after, monotonicNanos, available
- a thin layer over system.clock/sleep/timerOnce; unit-tested arithmetic
Remove the demo drivers hpet and bus (a teaching example belongs in the docs,
not shipped in the tree)
- system/drivers/ now holds only real drivers: pci-bus, ps2-bus, usb-xhci-bus
- device-manager end-to-end test repointed to pci-bus (asserts on kernel state:
the process table and the device tree, not a racy serial marker)
- device_register containment moved to a new in-kernel `containment` test
- the driver-model worked example moved inline into docs/drivers.md
Reorganize milestone docs into topic docs
- m17-m18 / m19-m20 / m21 plans dissolved into process-lifecycle, device-manager,
discovery, and acpi docs; new docs/power.md and docs/timers.md; ~20 citations
repointed; plan docs deleted
TSC reliability (apic.zig, smp.zig, cpu.zig, kernel.zig)
- check the invariant-TSC bit (CPUID 0x80000007 EDX[8]) on Intel and AMD
- cross-core "warp" check at SMP bring-up, pairwise BSP<->AP as each core comes up
- fall back to the HPET clocksource when the TSC is not invariant (a bare VM) or
not synchronized (a warp), switched continuously so time never jumps
- boot log reports the outcome; new tsc-sync test exercises the TSC + warp path
Verified: zig build; zig build test; 60/60 QEMU cases (incl. new containment and
tsc-sync).
Applications ask the device manager for the tree (enumerate: a header
plus ChildEntry records) and subscribe to published add/remove events by
handing their endpoint over as the call's capability — the input-service
pattern; events are the same ChildAdded/ChildRemoved structs the bus
drivers send, one encoding in both directions. device-list is the first
client: it prints the tree, subscribes, and narrates the events through
a driver restart. The protocol's message maximum is capped at the
kernel's IPC MESSAGE_MAXIMUM (256 bytes, ten entries per reply; paging
joins the protocol when a tree outgrows one message). The startUserTask
debug print is gone: it wrote to serial unserialized against user-space
lines and sheared concurrent log markers in half — the root cause of the
scenario flakes.
child_added/child_removed join the device-manager protocol. The driver
maps its register BAR (resource 0 is the ECAM config space; the walk
starts at 1), reads CAPLENGTH and HCSPARAMS1, and reads one PORTSC per
port: the connect bit and speed class come straight from hardware, no
rings needed to see the devices. The manager mirrors reported children
keyed by (parent, port), remembers which instance reported each, and
prunes a dead reporter's children before deciding the restart — the
children describe protocol state that died with the process. The
usb-report scenario drives the whole loop: two QEMU devices reported,
reporter killed, children pruned, driver respawned with backoff, and the
new instance re-claims, re-scans, and re-reports.
The manager is now a harness service on the well-known .device_manager
endpoint. Every driver spawns supervised; drivers with an assignment must
hello (device-manager-protocol, versioned) within a deadline enforced by
a timer sweep. Exit reasons drive the restart decision: clean exits stay
down, faults restart with 300/600/1200ms backoff, and three fast deaths
mark a driver failed instead of respawning forever. usb-xhci-bus is the
first conforming driver; the crash-test fixture claims a device, hellos,
and faults on purpose — each respawn re-proving claim release on death
through the manager's own path. maximum_tasks grows 16 -> 32: the
initial-ramdisk sweep (15 binaries at once) was intermittently
overflowing the static pool.
Signals over IPC (POSIX concepts, message delivery), published exit events,
the stable runtime.process interface, and the device manager as tree +
matcher + supervisor. All open questions settled; docs/m17-m18-plan.md is
the phase-by-phase execution plan.
Daniel Samson