Fix: raise on manual fiber resume from sleep

src/crystal/event_loop/iocp.cr

@@ -131,9 +131,7 @@ class Crystal::EventLoop::IOCP < Crystal::EventLoop
     fiber = timer.value.fiber
 
     case timer.value.type
-    in .sleep?
-      # nothing to do
-    in .timeout?
+    in .sleep?, .timeout?
       timer.value.timed_out!
     in .select_timeout?
       return unless select_action = fiber.timeout_select_action
@@ -188,6 +186,15 @@ class Crystal::EventLoop::IOCP < Crystal::EventLoop
     timer = Timer.new(:sleep, Fiber.current, duration)
     add_timer(pointerof(timer))
     Fiber.suspend
+
+    # safety check
+    return if timer.timed_out?
+
+    # try to avoid a double resume if possible, but another thread might be
+    # running the evloop and dequeue the event in parallel, so a "can't resume
+    # dead fiber" can still happen in a MT execution context.
+    delete_timer(pointerof(timer))
+    raise "BUG: #{timer.fiber} called sleep but was manually resumed before the timer expired!"
   end
 
   # Suspend the current fiber for *duration* and returns true if the timer

src/crystal/event_loop/polling.cr

@@ -137,6 +137,15 @@ abstract class Crystal::EventLoop::Polling < Crystal::EventLoop
     event = Event.new(:sleep, Fiber.current, timeout: duration)
     add_timer(pointerof(event))
     Fiber.suspend
+
+    # safety check
+    return if event.timed_out?
+
+    # try to avoid a double resume if possible, but another thread might be
+    # running the evloop and dequeue the event in parallel, so a "can't resume
+    # dead fiber" can still happen in a MT execution context.
+    delete_timer(pointerof(event))
+    raise "BUG: #{event.fiber} called sleep but was manually resumed before the timer expired!"
   end
 
   def create_timeout_event(fiber : Fiber) : FiberEvent
@@ -551,7 +560,7 @@ abstract class Crystal::EventLoop::Polling < Crystal::EventLoop
       return unless select_action.time_expired?
       fiber.@timeout_event.as(FiberEvent).clear
     when .sleep?
-      # nothing to do
+      event.value.timed_out!
     else
       raise RuntimeError.new("BUG: unexpected event in timers: #{event.value}%s\n")
     end