ps: initial process subsystem

src/proc/private.zig

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+const r = @import("root");
+const ke = r.ke;
+const ki = ke.private;
+const mm = r.mm;
+
+pub const thread = @import("thread.zig");
+
+pub var turnstile_zone: mm.zone.TypedZone(ki.turnstile.Turnstile) = undefined;
+
+fn turnstile_ctor(ts: *ki.turnstile.Turnstile) void {
+    ts.* = .{
+        .link = undefined,
+        .next_free = null,
+        .obj = undefined,
+        .owner = null,
+        .boost_link = undefined,
+        .donated = null,
+        .queues = undefined,
+        .waiters = 0,
+    };
+    ts.queues[0].init();
+    ts.queues[1].init();
+}
+
+/// Initialize the process subsystem.
+pub fn init() void {
+    turnstile_zone.init("turnstiles", .{ .ctor = turnstile_ctor });
+}

src/proc/root.zig

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+//! Higher-level process management.
+
+// === Exported modules ===
+pub const private = @import("private.zig");
+
+const p = private;
+
+// === Exported types ===
+pub const Thread = p.thread.Thread;
+
+// === Exported interfaces ===
+pub const thread = struct {
+    pub const create_kernel = p.thread.create_kernel;
+};
+
+pub const init = p.init;

src/proc/thread.zig

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+//! Higher-level thread management.
+const r = @import("root");
+const psp = r.ps.private;
+const ke = r.ke;
+const ki = ke.private;
+const mm = r.mm;
+
+const kernel_thread_stack_size = r.kib(16);
+
+/// Higher-level wrapper over a thread.
+pub const Thread = struct {
+    /// Lower-level part of the thread.
+    kern: ke.Thread,
+};
+
+/// Create a kernel thread.
+/// - `prio`: base priority of the thread.
+/// - `entry`: entry point.
+/// - `arg`: argument passed to `entry`.
+pub fn create_kernel(prio: u8, entry: *const fn (arg: ?*anyopaque) void, arg: ?*anyopaque) !*Thread {
+    var td = try mm.zone.gpa.create(Thread);
+    const stack = try mm.heap.alloc(kernel_thread_stack_size);
+
+    td.kern.init(@intFromPtr(stack), kernel_thread_stack_size, prio, entry, arg);
+    td.kern.turnstile = try psp.turnstile_zone.create();
+
+    return td;
+}