Release a dead process's device claims (M17.1)

Every path out of a process (exit, fault, kill) now releases its device
claims alongside its IRQ and MSI bindings, so a restarted driver can claim
its hardware again — the cleanup half of process-lifecycle.md's iron rule 1.
MSI vectors were already swept by irq.releaseOwner; claims were the gap.
The claim-release test proves kill -> release -> re-claim, plus the broker
release in isolation.

docs/m17-m18-plan.md

@@ -29,7 +29,9 @@ only when its definition of green holds.
 - [x] **Phase 0** — baseline: docs committed, feat/usb merged to main, pushed;
       `usb-xhci-libary.zig` renamed to `usb-xhci-library.zig`; existing QEMU
       suite green from the worktree (48/48, 2026-07-12).
-- [ ] **M17.1** — kernel releases claims/MSI on death (branch `feat/process-lifecycle`)
+- [x] **M17.1** — kernel releases claims/MSI on death (claims: `releaseAllOwnedBy`
+      in the reap; MSI was already swept by `irq.releaseOwner`; `claim-release`
+      test; suite 49/49)
 - [ ] **M17.2** — exit reasons
 - [ ] **M17.3** — published exit events + VFS subscriber
 - [ ] **M17.4** — signals, timer notifications, `runtime.process`, the service harness

docs/process-management.md

@@ -95,8 +95,11 @@ the architecture layer calls up into `tick`.
 
 ## Known gaps (bring-up honesty)
 
-- Device **claims** are not released on death (pre-existing: the fault path has
+- ~~Device claims are not released on death~~ Closed (M17.1): every path out of a
-  the same gap) — a killed driver's device stays claimed until reboot.
+  process releases its device claims alongside its IRQ and MSI bindings
+  (`releaseTaskResourcesLocked`), so a restarted driver can claim its hardware
+  again — the cleanup half of [process-lifecycle.md](process-lifecycle.md)'s iron
+  rule 1. The `claim-release` test proves the kill → release → re-claim cycle.
 - Kernel stacks of dead tasks are leaked, as on every exit path (no reaper yet).
 - There is no exit *status* in the notification, only the id; a supervisor that
   needs the code can grow a wait-style call later.
@@ -109,4 +112,5 @@ the architecture layer calls up into `tick`.
 `process-list` (enumerate), `process-kill` (kernel-level kill paths, refusals,
 notifications), `supervision` (the whole user-side surface via the process-test
 service: spawn supervised → enumerate → kill blocked and spinning children →
-notifications → gone). See test/qemu_test.py.
+notifications → gone), `claim-release` (a killed claim-holder's device is
+claimable again). See test/qemu_test.py.

system/kernel/devices-broker.zig

@@ -104,6 +104,19 @@ pub fn ownerOf(id: u64) ?u32 {
     return claimed[@intCast(id)];
 }
 
+/// Release every claim held by `owner` — called by the process layer on every
+/// path out of a process (exit, fault, kill), so a restarted driver can claim its
+/// hardware again (docs/process-lifecycle.md iron rule 1: cleanup is the kernel's
+/// job). The devices stay in the table — they describe hardware, which did not go
+/// away — only their ownership clears.
+pub fn releaseAllOwnedBy(owner: u32) void {
+    for (claimed[0..count]) |*slot| {
+        if (slot.*) |o| {
+            if (o == owner) slot.* = null;
+        }
+    }
+}
+
 /// Resource `index` of device `id`, or null if out of range.
 pub fn resourceOf(id: u64, index: u64) ?device_abi.ResourceDescriptor {
     if (id >= count) return null;

system/kernel/process.zig

@@ -552,7 +552,11 @@ pub var fault_kill_count: u64 = 0;
 ///   endpoint reference destroys the Endpoint, and a still-bound GSI would have an
 ///   ISR call notifyFromIsr on freed memory the next time the device fired.
 ///   `releaseOwner` also leaves the line masked, so a dead driver's device goes
-///   quiet rather than storming.
+///   quiet rather than storming. (It drops MSI vectors by the same owner sweep.)
+/// - Device claims are released with the IRQ bindings, so a restarted driver can
+///   claim the same hardware again — the cleanup half of process-lifecycle.md's
+///   iron rule 1. Claims hold no pointers, so ordering is free; they go here so
+///   the exit notification (below, last) observes a fully-released child.
 /// - A client this task still owes a reply to (it died between receive and reply)
 ///   is failed with -EPEER rather than left blocked forever — a dead server must
 ///   not hang its callers.
@@ -566,6 +570,7 @@ pub var fault_kill_count: u64 = 0;
 /// Precondition: the big kernel lock is held.
 fn releaseTaskResourcesLocked(t: *scheduler.Task) void {
     irq.releaseOwner(t.id);
+    devices_broker.releaseAllOwnedBy(t.id);
     if (t.ipc_client) |client| {
         t.ipc_client = null;
         client.ipc_status = -ipc.EPEER;

system/kernel/tests.zig

@@ -132,6 +132,8 @@ pub fn run(case: []const u8, boot_information: *const BootInformation) void {
         processKillTest(boot_information);
     } else if (eql(case, "supervision")) {
         supervisionTest(boot_information);
+    } else if (eql(case, "claim-release")) {
+        claimReleaseTest(boot_information);
     } else if (eql(case, "initial-ramdisk")) {
         initialRamdiskTest(boot_information);
     } else if (eql(case, "vfs")) {
@@ -1454,6 +1456,61 @@ fn processKillTest(boot_information: *const BootInformation) void {
     result();
 }
 
+/// M17.1: a dead process's device claims are released by the reap, so a restarted
+/// driver can claim its hardware again (docs/process-lifecycle.md iron rule 1).
+/// First the broker release in isolation — two owners, one released, the other's
+/// claim must survive. Then the death-path wiring with a real child: the claim is
+/// made on the child's behalf (the broker is kernel-callable), the child is
+/// killed, and once the exit notification arrives — posted last, after release —
+/// the device must be unclaimed and claimable again.
+fn claimReleaseTest(boot_information: *const BootInformation) void {
+    log("DANOS-TEST-BEGIN: claim-release\n", .{});
+
+    var buffer: [2]device_abi.DeviceDescriptor = undefined;
+    const total = devices_broker.enumerate(&buffer);
+    check("the device tree is seeded (>= 2 devices)", total >= 2);
+    if (total < 2) {
+        result();
+        return;
+    }
+
+    // The broker release in isolation.
+    check("device 0 claimed by owner 111", devices_broker.claim(0, 111));
+    check("device 1 claimed by owner 222", devices_broker.claim(1, 222));
+    devices_broker.releaseAllOwnedBy(111);
+    check("owner 111's claim is released", devices_broker.ownerOf(0) == null);
+    check("owner 222's claim survives", (devices_broker.ownerOf(1) orelse 0) == 222);
+    devices_broker.releaseAllOwnedBy(222);
+    check("cleanup released owner 222", devices_broker.ownerOf(1) == null);
+
+    // The death-path wiring: a real process dies holding a claim.
+    check("bootloader handed over /system/services/init", boot_information.init_len != 0);
+    if (boot_information.init_len == 0) {
+        result();
+        return;
+    }
+    const image = @as([*]const u8, @ptrFromInt(boot_handoff.physicalToVirtual(boot_information.init_base)))[0..boot_information.init_len];
+    const me = scheduler.currentId();
+    const endpoint = ipcsync.createIpcEndpoint() orelse {
+        check("exit endpoint allocated", false);
+        result();
+        return;
+    };
+    const child = process.spawnProcessSupervised(image, 4, &.{"/system/services/init"}, me, endpoint) catch 0;
+    check("supervised child spawned", child != 0);
+    check("device 0 claimed on the child's behalf", devices_broker.claim(0, child));
+
+    check("the kill is accepted", process.killProcess(me, child) == 0);
+    var badge: u64 = 0;
+    var received_cap: u64 = 0;
+    _ = ipcsync.replyWait(endpoint, 0, 0, 0, 0, abi.no_cap, &badge, &received_cap);
+    check("the exit notification arrived", badge == abi.notify_badge_bit | abi.notify_exit_bit | child);
+    check("death released the child's claim", devices_broker.ownerOf(0) == null);
+    check("the device is claimable again", devices_broker.claim(0, me));
+    devices_broker.releaseAllOwnedBy(me);
+    result();
+}
+
 /// The whole user-side surface at once: spawn process-test's supervisor role,
 /// which — entirely from ring 3 — creates an exit endpoint, spawns its two
 /// children supervised, sees them in process_enumerate, kills them (one blocked,

test/qemu_test.py

@@ -240,6 +240,12 @@ CASES = [
      "smp":    4,
      "expect": r"DANOS-TEST-RESULT: PASS",
      "fail":   r"DANOS-TEST-RESULT: FAIL"},
+    # M17.1: a dead process's device claims are released by the reap — kill a child
+    # holding a claim, the device must be claimable again (process-lifecycle.md).
+    {"name": "claim-release",
+     "smp":    4,
+     "expect": r"DANOS-TEST-RESULT: PASS",
+     "fail":   r"DANOS-TEST-RESULT: FAIL"},
     # The initial_ramdisk: the loader ferries a bundle of user binaries; the kernel parses
     # it and spawns each as a ring-3 process (here the VFS-server stub heartbeats).
     {"name": "initial-ramdisk",