have to use an async handle to wake up event loop for max timer

src/max_timer.zig

@@ -25,6 +25,10 @@ pub fn MaxTimer(comptime cb: fn (*libuv.Timer) void) type {
         /// The last time this timer ran.
         last: u64 = 0,
 
+        /// This handle is used to wake up the event loop when the timer
+        /// is restarted.
+        async_h: libuv.Async,
+
         pub fn init(
             loop: libuv.Loop,
             data: ?*anyopaque,
@@ -35,6 +39,13 @@ pub fn MaxTimer(comptime cb: fn (*libuv.Timer) void) type {
             var timer = try libuv.Timer.init(alloc, loop);
             timer.setData(data);
 
+            // The async handle is used to wake up the event loop. This is
+            // necessary since stop/starting a timer doesn't trigger the
+            // poll on the backend fd.
+            var async_h = try libuv.Async.init(alloc, loop, (struct {
+                fn callback(_: *libuv.Async) void {}
+            }).callback);
+
             // The maximum time can't be less than the interval otherwise this
             // will just constantly fire.
             if (max < min) return error.MaxShorterThanTimer;
@@ -42,17 +53,24 @@ pub fn MaxTimer(comptime cb: fn (*libuv.Timer) void) type {
                 .timer = timer,
                 .min = min,
                 .max = max,
+                .async_h = async_h,
             };
         }
 
         pub fn deinit(self: *Self) void {
+            self.async_h.close((struct {
+                fn callback(h: *libuv.Async) void {
+                    const alloc = h.loop().getData(Allocator).?.*;
+                    h.deinit(alloc);
+                }
+            }).callback);
+
             self.timer.close((struct {
                 fn callback(t: *libuv.Timer) void {
                     const alloc = t.loop().getData(Allocator).?.*;
                     t.deinit(alloc);
                 }
             }).callback);
-            self.* = undefined;
         }
 
         /// This should be called from the callback to update the last called time.
@@ -70,6 +88,10 @@ pub fn MaxTimer(comptime cb: fn (*libuv.Timer) void) type {
             // a tick as soon as possible.
             if (!try self.timer.isActive()) {
                 try self.timer.start(cb, self.min, self.min);
+
+                // We have to send an async message to wake up the
+                // event loop. Starting a timer doesn't write to the fd.
+                try self.async_h.send();
                 return;
             }