WIP

lib/std/Io/EventLoop.zig

@@ -5,6 +5,7 @@ const Allocator = std.mem.Allocator;
 const Io = std.Io;
 const EventLoop = @This();
 const Alignment = std.mem.Alignment;
+const IoUring = std.os.linux.IoUring;
 
 gpa: Allocator,
 mutex: std.Thread.Mutex,
@@ -13,18 +14,27 @@ queue: std.DoublyLinkedList(void),
 free: std.DoublyLinkedList(void),
 main_context: Context,
 exit_awaiter: ?*Fiber,
-idle_count: usize,
 threads: std.ArrayListUnmanaged(Thread),
+/// 1 bit per thread, same order as `thread_index`.
+idle_iourings: []usize,
 
-threadlocal var current_idle_context: *Context = undefined;
-threadlocal var current_context: *Context = undefined;
+threadlocal var thread_index: u32 = undefined;
 
 /// Empirically saw 10KB being used by the self-hosted backend for logging.
 const idle_stack_size = 32 * 1024;
 
+const io_uring_entries = 64;
+
 const Thread = struct {
     thread: std.Thread,
     idle_context: Context,
+    current_idle_context: *Context,
+    current_context: *Context,
+    io_uring: IoUring,
+
+    fn currentFiber(thread: *Thread) *Fiber {
+        return @fieldParentPtr("context", thread.current_context);
+    }
 };
 
 const Fiber = struct {
@@ -83,16 +93,25 @@ pub fn io(el: *EventLoop) Io {
         .vtable = &.{
             .@"async" = @"async",
             .@"await" = @"await",
+            .createFile = createFile,
+            .openFile = openFile,
+            .closeFile = closeFile,
+            .read = read,
+            .write = write,
         },
     };
 }
 
-pub fn init(el: *EventLoop, gpa: Allocator) error{OutOfMemory}!void {
-    const threads_bytes = ((std.Thread.getCpuCount() catch 1) -| 1) * @sizeOf(Thread);
+pub fn init(el: *EventLoop, gpa: Allocator) !void {
+    const n_threads: usize = @max((std.Thread.getCpuCount() catch 1), 1);
+    const threads_bytes = n_threads * @sizeOf(Thread);
     const idle_context_offset = std.mem.alignForward(usize, threads_bytes, @alignOf(Context));
     const idle_stack_end_offset = std.mem.alignForward(usize, idle_context_offset + idle_stack_size, std.heap.page_size_max);
     const allocated_slice = try gpa.alignedAlloc(u8, @max(@alignOf(Thread), @alignOf(Context)), idle_stack_end_offset);
     errdefer gpa.free(allocated_slice);
+    const idle_iourings = try gpa.alloc(usize, (n_threads + @bitSizeOf(usize) - 1) / @bitSizeOf(usize));
+    errdefer gpa.free(idle_iourings);
+    @memset(idle_iourings, 0);
     el.* = .{
         .gpa = gpa,
         .mutex = .{},
@@ -101,9 +120,11 @@ pub fn init(el: *EventLoop, gpa: Allocator) error{OutOfMemory}!void {
         .free = .{},
         .main_context = undefined,
         .exit_awaiter = null,
-        .idle_count = 0,
         .threads = .initBuffer(@ptrCast(allocated_slice[0..threads_bytes])),
+        .idle_iourings = idle_iourings,
     };
+    const main_thread = el.threads.addOneAssumeCapacity();
+    main_thread.io_uring = try IoUring.init(io_uring_entries, 0);
     const main_idle_context: *Context = @alignCast(std.mem.bytesAsValue(Context, allocated_slice[idle_context_offset..][0..@sizeOf(Context)]));
     const idle_stack_end: [*]align(@max(@alignOf(Thread), @alignOf(Context))) usize = @alignCast(@ptrCast(allocated_slice[idle_stack_end_offset..].ptr));
     (idle_stack_end - 1)[0..1].* = .{@intFromPtr(el)};
@@ -113,9 +134,9 @@ pub fn init(el: *EventLoop, gpa: Allocator) error{OutOfMemory}!void {
         .rip = @intFromPtr(&mainIdleEntry),
     };
     std.log.debug("created main idle {*}", .{main_idle_context});
-    current_idle_context = main_idle_context;
+    main_thread.current_idle_context = main_idle_context;
     std.log.debug("created main {*}", .{&el.main_context});
-    current_context = &el.main_context;
+    main_thread.current_context = &el.main_context;
 }
 
 pub fn deinit(el: *EventLoop) void {
@@ -125,14 +146,21 @@ pub fn deinit(el: *EventLoop) void {
         const free_fiber: *Fiber = @alignCast(@fieldParentPtr("queue_node", free_node));
         el.gpa.free(free_fiber.allocatedSlice());
     }
-    const idle_context_offset = std.mem.alignForward(usize, el.threads.items.len * @sizeOf(Thread), @alignOf(Context));
+    const idle_context_offset = std.mem.alignForward(usize, el.threads.capacity * @sizeOf(Thread), @alignOf(Context));
     const idle_stack_end = std.mem.alignForward(usize, idle_context_offset + idle_stack_size, std.heap.page_size_max);
     const allocated_ptr: [*]align(@max(@alignOf(Thread), @alignOf(Context))) u8 = @alignCast(@ptrCast(el.threads.items.ptr));
-    for (el.threads.items) |*thread| thread.thread.join();
+    for (el.threads.items[1..]) |*thread| thread.thread.join();
     el.gpa.free(allocated_ptr[0..idle_stack_end]);
 }
 
-fn yield(el: *EventLoop, optional_fiber: ?*Fiber, register_awaiter: ?*?*Fiber) void {
+const PendingTask = union(enum) {
+    none,
+    register_awaiter: *?*Fiber,
+    io_uring_submit: *IoUring,
+};
+
+fn yield(el: *EventLoop, optional_fiber: ?*Fiber, pending_task: PendingTask) void {
+    const thread: *Thread = &el.threads.items[thread_index];
     const ready_context: *Context = ready_context: {
         const ready_fiber: *Fiber = optional_fiber orelse if (ready_node: {
             el.mutex.lock();
@@ -141,13 +169,13 @@ fn yield(el: *EventLoop, optional_fiber: ?*Fiber, register_awaiter: ?*?*Fiber) v
         }) |ready_node|
             @alignCast(@fieldParentPtr("queue_node", ready_node))
         else
-            break :ready_context current_idle_context;
+            break :ready_context thread.current_idle_context;
         break :ready_context &ready_fiber.context;
     };
     const message: SwitchMessage = .{
-        .prev_context = current_context,
+        .prev_context = thread.current_context,
         .ready_context = ready_context,
-        .register_awaiter = register_awaiter,
+        .pending_task = pending_task,
     };
     std.log.debug("switching from {*} to {*}", .{ message.prev_context, message.ready_context });
     contextSwitch(&message).handle(el);
@@ -156,6 +184,11 @@ fn yield(el: *EventLoop, optional_fiber: ?*Fiber, register_awaiter: ?*?*Fiber) v
 fn schedule(el: *EventLoop, fiber: *Fiber) void {
     el.mutex.lock();
     el.queue.append(&fiber.queue_node);
+    //for (el.idle_iourings) |*int| {
+    //    const idler_subset = @atomicLoad(usize, int, .unordered);
+    //    if (idler_subset == 0) continue;
+    //
+    //}
     if (el.idle_count > 0) {
         el.mutex.unlock();
         el.cond.signal();
@@ -167,7 +200,7 @@ fn schedule(el: *EventLoop, fiber: *Fiber) void {
     thread.thread = std.Thread.spawn(.{
         .stack_size = idle_stack_size,
         .allocator = el.gpa,
-    }, threadEntry, .{ el, thread }) catch {
+    }, threadEntry, .{ el, el.threads.items.len - 1 }) catch {
         el.threads.items.len -= 1;
         return;
     };
@@ -187,38 +220,61 @@ fn mainIdle(el: *EventLoop, message: *const SwitchMessage) callconv(.withStackAl
     unreachable; // switched to dead fiber
 }
 
-fn threadEntry(el: *EventLoop, thread: *Thread) void {
+fn threadEntry(el: *EventLoop, index: usize) void {
+    thread_index = index;
+    const thread: *Thread = &el.threads.items[index];
     std.log.debug("created thread idle {*}", .{&thread.idle_context});
-    current_idle_context = &thread.idle_context;
-    current_context = &thread.idle_context;
+    thread.io_uring = IoUring.init(io_uring_entries, 0) catch |err| {
+        std.log.warn("exiting worker thread during init due to io_uring init failure: {s}", .{@errorName(err)});
+        return;
+    };
+    thread.current_idle_context = &thread.idle_context;
+    thread.current_context = &thread.idle_context;
     _ = el.idle();
 }
 
 fn idle(el: *EventLoop) *Fiber {
+    const thread: *Thread = &el.threads.items[thread_index];
+    // The idle fiber only runs on one thread.
+    const iou = &thread.io_uring;
+    var cqes_buffer: [io_uring_entries]std.os.linux.io_uring_cqe = undefined;
+
     while (true) {
         el.yield(null, null);
         if (@atomicLoad(?*Fiber, &el.exit_awaiter, .acquire)) |exit_awaiter| {
             el.cond.broadcast();
             return exit_awaiter;
         }
-        el.mutex.lock();
-        defer el.mutex.unlock();
-        el.idle_count += 1;
-        defer el.idle_count -= 1;
-        el.cond.wait(&el.mutex);
+        // TODO add uring to bit set
+        const n = iou.copy_cqes(&cqes_buffer, 1) catch @panic("TODO handle copy_cqes error");
+        const cqes = cqes_buffer[0..n];
+        for (cqes) |cqe| {
+            const fiber: *Fiber = @ptrFromInt(cqe.user_data);
+            const res: *i32 = @ptrCast(@alignCast(fiber.resultPointer()));
+            res.* = cqe.res;
+            el.schedule(fiber);
+        }
     }
 }
 
 const SwitchMessage = extern struct {
     prev_context: *Context,
     ready_context: *Context,
-    register_awaiter: ?*?*Fiber,
+    pending_task: PendingTask,
 
     fn handle(message: *const SwitchMessage, el: *EventLoop) void {
-        current_context = message.ready_context;
-        if (message.register_awaiter) |awaiter| {
+        const thread: *Thread = &el.threads.items[thread_index];
+        thread.current_context = message.ready_context;
+        switch (message.pending_task) {
+            .none => {},
+            .register_awaiter => |awaiter| {
                 const prev_fiber: *Fiber = @alignCast(@fieldParentPtr("context", message.prev_context));
                 if (@atomicRmw(?*Fiber, awaiter, .Xchg, prev_fiber, .acq_rel) == Fiber.finished) el.schedule(prev_fiber);
+            },
+            .io_uring_submit => |iou| {
+                _ = iou.flush_sq();
+                // TODO: determine whether this return value should be used
+            },
         }
     }
 };
@@ -357,3 +413,132 @@ pub fn @"await"(userdata: ?*anyopaque, any_future: *std.Io.AnyFuture, result: []
     @memcpy(result, future_fiber.resultPointer());
     event_loop.recycle(future_fiber);
 }
+
+pub fn createFile(userdata: ?*anyopaque, dir: std.fs.Dir, sub_path: []const u8, flags: std.fs.File.CreateFlags) std.fs.File.OpenError!std.fs.File {
+    _ = userdata;
+    _ = dir;
+    _ = sub_path;
+    _ = flags;
+    @panic("TODO");
+}
+
+pub fn openFile(userdata: ?*anyopaque, dir: std.fs.Dir, sub_path: []const u8, flags: std.fs.File.OpenFlags) std.fs.File.OpenError!std.fs.File {
+    const el: *EventLoop = @ptrCast(@alignCast(userdata));
+
+    const posix = std.posix;
+    const sub_path_c = try posix.toPosixPath(sub_path);
+
+    var os_flags: posix.O = .{
+        .ACCMODE = switch (flags.mode) {
+            .read_only => .RDONLY,
+            .write_only => .WRONLY,
+            .read_write => .RDWR,
+        },
+    };
+
+    if (@hasField(posix.O, "CLOEXEC")) os_flags.CLOEXEC = true;
+    if (@hasField(posix.O, "LARGEFILE")) os_flags.LARGEFILE = true;
+    if (@hasField(posix.O, "NOCTTY")) os_flags.NOCTTY = !flags.allow_ctty;
+
+    // Use the O locking flags if the os supports them to acquire the lock
+    // atomically.
+    const has_flock_open_flags = @hasField(posix.O, "EXLOCK");
+    if (has_flock_open_flags) {
+        // Note that the NONBLOCK flag is removed after the openat() call
+        // is successful.
+        switch (flags.lock) {
+            .none => {},
+            .shared => {
+                os_flags.SHLOCK = true;
+                os_flags.NONBLOCK = flags.lock_nonblocking;
+            },
+            .exclusive => {
+                os_flags.EXLOCK = true;
+                os_flags.NONBLOCK = flags.lock_nonblocking;
+            },
+        }
+    }
+    const have_flock = @TypeOf(posix.system.flock) != void;
+
+    if (have_flock and !has_flock_open_flags and flags.lock != .none) {
+        @panic("TODO");
+    }
+
+    if (has_flock_open_flags and flags.lock_nonblocking) {
+        @panic("TODO");
+    }
+
+    const thread: *Thread = &el.threads.items[thread_index];
+    const iou = &thread.io_uring;
+    const sqe = getSqe(iou);
+    const fiber = thread.currentFiber();
+
+    sqe.prep_openat(dir.fd, &sub_path_c, os_flags, 0);
+    sqe.user_data = @intFromPtr(fiber);
+
+    el.yield(null, .{ .io_uring_submit = iou });
+
+    const result: *i32 = @alignCast(@ptrCast(fiber.resultPointer()[0..@sizeOf(posix.fd_t)]));
+    const rc = result.*;
+    switch (errno(rc)) {
+        .SUCCESS => return .{ .handle = rc },
+        .INTR => @panic("TODO is this reachable?"),
+        .CANCELED => @panic("TODO figure out how this error code fits into things"),
+
+        .FAULT => unreachable,
+        .INVAL => return error.BadPathName,
+        .BADF => unreachable,
+        .ACCES => return error.AccessDenied,
+        .FBIG => return error.FileTooBig,
+        .OVERFLOW => return error.FileTooBig,
+        .ISDIR => return error.IsDir,
+        .LOOP => return error.SymLinkLoop,
+        .MFILE => return error.ProcessFdQuotaExceeded,
+        .NAMETOOLONG => return error.NameTooLong,
+        .NFILE => return error.SystemFdQuotaExceeded,
+        .NODEV => return error.NoDevice,
+        .NOENT => return error.FileNotFound,
+        .NOMEM => return error.SystemResources,
+        .NOSPC => return error.NoSpaceLeft,
+        .NOTDIR => return error.NotDir,
+        .PERM => return error.PermissionDenied,
+        .EXIST => return error.PathAlreadyExists,
+        .BUSY => return error.DeviceBusy,
+        .OPNOTSUPP => return error.FileLocksNotSupported,
+        .AGAIN => return error.WouldBlock,
+        .TXTBSY => return error.FileBusy,
+        .NXIO => return error.NoDevice,
+        else => |err| return posix.unexpectedErrno(err),
+    }
+
+    return .{ .handle = result.* };
+}
+
+fn errno(signed: i32) std.posix.E {
+    const int = if (signed > -4096 and signed < 0) -signed else 0;
+    return @enumFromInt(int);
+}
+
+fn getSqe(iou: *IoUring) *std.os.linux.io_uring_sqe {
+    return iou.get_sqe() catch @panic("TODO: handle submission queue full");
+}
+
+pub fn closeFile(userdata: ?*anyopaque, file: std.fs.File) void {
+    _ = userdata;
+    _ = file;
+    @panic("TODO");
+}
+
+pub fn read(userdata: ?*anyopaque, file: std.fs.File, buffer: []u8) std.fs.File.ReadError!usize {
+    _ = userdata;
+    _ = file;
+    _ = buffer;
+    @panic("TODO");
+}
+
+pub fn write(userdata: ?*anyopaque, file: std.fs.File, buffer: []const u8) std.fs.File.WriteError!usize {
+    _ = userdata;
+    _ = file;
+    _ = buffer;
+    @panic("TODO");
+}