fix(ui): reset, bios load and rom load are properly thread safe

build.zig.zon

@@ -19,8 +19,8 @@
             .hash = "1220f48518ce22882e102255ed3bcdb7aeeb4891f50b2cdd3bd74b5b2e24d3149ba2",
         },
         .@"zba-util" = .{
-            .url = "https://git.musuka.dev/paoda/zba-util/archive/322c798e384a0d24cc84ffcfa2e4a3ca807798a0.tar.gz",
+            .url = "https://git.musuka.dev/paoda/zba-util/archive/14ea006f4ffae77a333de4993c89690ce94d4abc.tar.gz",
-            .hash = "12209ce0e729460b997706e47a53a32f1842672cd120189e612f4871731780a30ed0",
+            .hash = "1220f0d7c5802ae0a297844f96b2226ccc3d4d895277278e4345c3660161debbe85d",
         },
         .tomlz = .{
             .url = "https://github.com/mattyhall/tomlz/archive/47067cd7c902485f7d6e928331fd171ed47f72da.tar.gz",

src/core/emu.zig

@@ -6,8 +6,7 @@ const Scheduler = @import("scheduler.zig").Scheduler;
 const Arm7tdmi = @import("arm32").Arm7tdmi;
 const Bus = @import("Bus.zig");
 const Tracker = @import("../util.zig").FpsTracker;
-
+const Channel = @import("../util.zig").Queue;
-pub const Message = enum { Pause, Resume, Quit };
 
 const stepDmaTransfer = @import("cpu_util.zig").stepDmaTransfer;
 const isHalted = @import("cpu_util.zig").isHalted;
@@ -17,10 +16,27 @@ const Timer = std.time.Timer;
 pub const Synchro = struct {
     const AtomicBool = std.atomic.Atomic(bool);
 
+    // FIXME: This Enum ends up being really LARGE!!!
+    pub const Message = union(enum) {
+        rom_path: [std.fs.MAX_PATH_BYTES]u8,
+        bios_path: [std.fs.MAX_PATH_BYTES]u8,
+        restart: void,
+    };
+
     paused: AtomicBool = AtomicBool.init(true), // FIXME: can ui_busy and paused be the same?
     should_quit: AtomicBool = AtomicBool.init(false),
 
-    emu_access: std.Thread.Mutex = .{},
+    ch: Channel(Message),
+
+    pub fn init(allocator: std.mem.Allocator) !@This() {
+        const msg_buf = try allocator.alloc(Message, 1);
+        return .{ .ch = Channel(Message).init(msg_buf) };
+    }
+
+    pub fn deinit(self: *@This(), allocator: std.mem.Allocator) void {
+        allocator.free(self.ch.inner.buf);
+        self.* = undefined;
+    }
 };
 
 /// 4 Cycles in 1 dot
@@ -75,9 +91,10 @@ fn inner(comptime kind: RunKind, audio_sync: bool, cpu: *Arm7tdmi, scheduler: *S
             log.info("Emulation w/out video sync", .{});
 
             while (!sync.should_quit.load(.Monotonic)) {
+                handleChannel(cpu, &sync.ch);
                 if (sync.paused.load(.Monotonic)) continue;
 
-                runFrame(sync, scheduler, cpu);
+                runFrame(scheduler, cpu);
                 audioSync(audio_sync, bus_ptr.apu.stream, &bus_ptr.apu.is_buffer_full);
 
                 if (kind == .UnlimitedFPS) tracker.?.tick();
@@ -89,9 +106,10 @@ fn inner(comptime kind: RunKind, audio_sync: bool, cpu: *Arm7tdmi, scheduler: *S
             var wake_time: u64 = frame_period;
 
             while (!sync.should_quit.load(.Monotonic)) {
+                handleChannel(cpu, &sync.ch);
                 if (sync.paused.load(.Monotonic)) continue;
 
-                runFrame(sync, scheduler, cpu);
+                runFrame(scheduler, cpu);
                 const new_wake_time = videoSync(&timer, wake_time);
 
                 // Spin to make up the difference of OS scheduler innacuracies
@@ -109,10 +127,23 @@ fn inner(comptime kind: RunKind, audio_sync: bool, cpu: *Arm7tdmi, scheduler: *S
     }
 }
 
-pub fn runFrame(sync: *Synchro, sched: *Scheduler, cpu: *Arm7tdmi) void {
+inline fn handleChannel(cpu: *Arm7tdmi, channel: *Channel(Synchro.Message)) void {
-    sync.emu_access.lock();
+    const message = channel.pop() orelse return;
-    defer sync.emu_access.unlock();
 
+    switch (message) {
+        .rom_path => |path_buf| {
+            const path = std.mem.sliceTo(&path_buf, 0);
+            replaceGamepak(cpu, path) catch |e| log.err("failed to replace GamePak: {}", .{e});
+        },
+        .bios_path => |path_buf| {
+            const path = std.mem.sliceTo(&path_buf, 0);
+            replaceBios(cpu, path) catch |e| log.err("failed to replace BIOS: {}", .{e});
+        },
+        .restart => reset(cpu),
+    }
+}
+
+pub fn runFrame(sched: *Scheduler, cpu: *Arm7tdmi) void {
     const frame_end = sched.tick + cycles_per_frame;
 
     while (sched.tick < frame_end) {
@@ -249,21 +280,21 @@ pub const EmuThing = struct {
     }
 };
 
-pub fn reset(cpu: *Arm7tdmi) void {
+fn reset(cpu: *Arm7tdmi) void {
     // @breakpoint();
     cpu.sched.reset(); // Yes this is order sensitive, see the PPU reset for why
     cpu.bus.reset();
     cpu.reset();
 }
 
-pub fn replaceGamepak(cpu: *Arm7tdmi, file_path: []const u8) !void {
+fn replaceGamepak(cpu: *Arm7tdmi, file_path: []const u8) !void {
     const bus_ptr: *Bus = @ptrCast(@alignCast(cpu.bus.ptr));
 
     try bus_ptr.replaceGamepak(file_path);
     reset(cpu);
 }
 
-pub fn replaceBios(cpu: *Arm7tdmi, file_path: []const u8) !void {
+fn replaceBios(cpu: *Arm7tdmi, file_path: []const u8) !void {
     const bus_ptr: *Bus = @ptrCast(@alignCast(cpu.bus.ptr));
 
     const allocator = bus_ptr.bios.allocator;

src/imgui.zig

@@ -13,6 +13,7 @@ const Gui = @import("platform.zig").Gui;
 const Arm7tdmi = @import("arm32").Arm7tdmi;
 const Scheduler = @import("core/scheduler.zig").Scheduler;
 const Bus = @import("core/Bus.zig");
+const Synchro = @import("core/emu.zig").Synchro;
 
 const RingBuffer = @import("zba-util").RingBuffer;
 const Dimensions = @import("platform.zig").Dimensions;
@@ -70,12 +71,14 @@ pub const State = struct {
     }
 };
 
-pub fn draw(state: *State, win_dim: Dimensions, tex_id: GLuint, cpu: *Arm7tdmi) bool {
+pub fn draw(sync: *Synchro, state: *State, win_dim: Dimensions, tex_id: GLuint, cpu: *const Arm7tdmi) bool {
     const scn_scale = config.config().host.win_scale;
     const bus_ptr: *Bus = @ptrCast(@alignCast(cpu.bus.ptr));
 
     zgui.backend.newFrame(@floatFromInt(win_dim.width), @floatFromInt(win_dim.height));
 
+    state.title = handleTitle(&bus_ptr.pak.title);
+
     {
         _ = zgui.beginMainMenuBar();
         defer zgui.endMainMenuBar();
@@ -99,12 +102,18 @@ pub fn draw(state: *State, win_dim: Dimensions, tex_id: GLuint, cpu: *Arm7tdmi)
                 defer nfd.freePath(file_path);
 
                 log.info("user chose: \"{s}\"", .{file_path});
-                emu.replaceGamepak(cpu, file_path) catch |e| {
+
-                    log.err("failed to replace GamePak: {}", .{e});
+                const message = tmp: {
+                    var msg: Synchro.Message = .{ .rom_path = undefined };
+                    @memcpy(msg.rom_path[0..file_path.len], file_path);
+                    break :tmp msg;
+                };
+
+                sync.ch.push(message) catch |e| {
+                    log.err("failed to send file path to emu thread: {}", .{e});
                     break :blk;
                 };
 
-                state.title = handleTitle(&bus_ptr.pak.title);
                 state.emulation = .{ .Transition = .Active };
             }
 
@@ -121,8 +130,15 @@ pub fn draw(state: *State, win_dim: Dimensions, tex_id: GLuint, cpu: *Arm7tdmi)
                 defer nfd.freePath(file_path);
 
                 log.info("user chose: \"{s}\"", .{file_path});
-                emu.replaceBios(cpu, file_path) catch |e| {
+
-                    log.err("failed to replace BIOS: {}", .{e});
+                const message = tmp: {
+                    var msg: Synchro.Message = .{ .bios_path = undefined };
+                    @memcpy(msg.bios_path[0..file_path.len], file_path);
+                    break :tmp msg;
+                };
+
+                sync.ch.push(message) catch |e| {
+                    log.err("failed to send file path to emu thread: {}", .{e});
                     break :blk;
                 };
             }
@@ -149,7 +165,7 @@ pub fn draw(state: *State, win_dim: Dimensions, tex_id: GLuint, cpu: *Arm7tdmi)
             }
 
             if (zgui.menuItem("Restart", .{}))
-                emu.reset(cpu);
+                sync.ch.push(.restart) catch |e| log.err("failed to send restart req to emu thread: {}", .{e});
         }
 
         if (zgui.beginMenu("Stats", true)) {

src/main.zig

@@ -119,7 +119,8 @@ pub fn main() void {
     var gui = Gui.init(allocator, &bus.apu, title_ptr) catch |e| exitln("failed to init gui: {}", .{e});
     defer gui.deinit();
 
-    var sync: Synchro = .{};
+    var sync = Synchro.init(allocator) catch |e| exitln("failed to allocate sync types: {}", .{e});
+    defer sync.deinit(allocator);
 
     if (result.args.gdb != 0) {
         const Server = @import("gdbstub").Server;

src/platform.zig

@@ -207,9 +207,6 @@ pub const Gui = struct {
                     },
                 },
                 .Active => {
-                    sync.emu_access.lock();
-                    defer sync.emu_access.unlock();
-
                     // Add FPS count to the histogram
                     if (tracker) |t| self.state.fps_hist.push(t.value()) catch {};
 
@@ -228,9 +225,9 @@ pub const Gui = struct {
                     SDL.SDL_LockAudioDevice(self.audio.device);
                     defer SDL.SDL_UnlockAudioDevice(self.audio.device);
 
-                    zgui_redraw = imgui.draw(&self.state, win_dim, out_tex, cpu);
+                    zgui_redraw = imgui.draw(sync, &self.state, win_dim, out_tex, cpu);
                 },
-                .Inactive => zgui_redraw = imgui.draw(&self.state, win_dim, out_tex, cpu),
+                .Inactive => zgui_redraw = imgui.draw(sync, &self.state, win_dim, out_tex, cpu),
             }
 
             if (zgui_redraw) {

src/util.zig

@@ -295,3 +295,31 @@ pub const FrameBuffer = struct {
         return self.layers[if (dev == .Emulator) self.current else ~self.current];
     }
 };
+
+const RingBuffer = @import("zba-util").RingBuffer;
+
+// TODO: Lock Free Queue?
+pub fn Queue(comptime T: type) type {
+    return struct {
+        inner: RingBuffer(T),
+        mtx: std.Thread.Mutex = .{},
+
+        pub fn init(buf: []T) @This() {
+            return .{ .inner = RingBuffer(T).init(buf) };
+        }
+
+        pub fn push(self: *@This(), value: T) !void {
+            self.mtx.lock();
+            defer self.mtx.unlock();
+
+            try self.inner.push(value);
+        }
+
+        pub fn pop(self: *@This()) ?T {
+            self.mtx.lock();
+            defer self.mtx.unlock();
+
+            return self.inner.pop();
+        }
+    };
+}