From 4e4e0fb1724869426395552a295c144250d4286d Mon Sep 17 00:00:00 2001
From: Ayke van Laethem <aykevanlaethem@gmail.com>
Date: Sun, 1 Dec 2024 13:49:46 +0100
Subject: [PATCH] runtime: use exitGoroutine instead of deadlock

This makes the meaning more clear. And while the behavior is currently
the same, when we start to use threads we should actually exit the
goroutine when calling runtime.Goexit() instead of just leaving it
deadlocked.
---
 src/runtime/panic.go                 |  4 ++--
 src/runtime/scheduler_cooperative.go | 13 +++++++++++--
 src/runtime/scheduler_none.go        |  6 ++++++
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/runtime/panic.go b/src/runtime/panic.go
index 9ae1f982b9..bea2e005ba 100644
--- a/src/runtime/panic.go
+++ b/src/runtime/panic.go
@@ -71,9 +71,9 @@ func panicOrGoexit(message interface{}, panicking panicState) {
 		}
 	}
 	if panicking == panicGoexit {
-		// Call to Goexit() instead of a panic.
+		// This is a call to Goexit() instead of a panic.
 		// Exit the goroutine instead of printing a panic message.
-		deadlock()
+		exitGoroutine()
 	}
 	printstring("panic: ")
 	printitf(message)
diff --git a/src/runtime/scheduler_cooperative.go b/src/runtime/scheduler_cooperative.go
index 3cb1e3f987..f5042b6b31 100644
--- a/src/runtime/scheduler_cooperative.go
+++ b/src/runtime/scheduler_cooperative.go
@@ -45,9 +45,18 @@ var (
 //
 //go:noinline
 func deadlock() {
-	// call yield without requesting a wakeup
+	exitGoroutine()
+}
+
+func exitGoroutine() {
+	// Pause the goroutine without a way for it to wake up.
+	// This makes the goroutine unreachable, and should eventually get it
+	// cleaned up by the GC.
 	task.Pause()
-	panic("unreachable")
+
+	// We will never return from task.Pause(). Make sure the compiler knows
+	// this.
+	trap()
 }
 
 // Add this task to the end of the run queue.
diff --git a/src/runtime/scheduler_none.go b/src/runtime/scheduler_none.go
index dc4b03b6e2..1c2da7eb0a 100644
--- a/src/runtime/scheduler_none.go
+++ b/src/runtime/scheduler_none.go
@@ -36,6 +36,12 @@ func deadlock() {
 	runtimePanic("all goroutines are asleep - deadlock!")
 }
 
+func exitGoroutine() {
+	// There is only one goroutine, which would exit, so that leads to a
+	// deadlock.
+	deadlock()
+}
+
 func scheduleTask(t *task.Task) {
 	// Pause() will panic, so this should not be reachable.
 }