runtime: do not omit stack trace of goroutine that handles async events

On wasm there is a special goroutine that handles asynchronous events.
Blocking this goroutine often causes a deadlock. However, the stack
trace of this goroutine was omitted when printing the deadlock error.

This change adds an exception so the goroutine is not considered as
an internal system goroutine and the stack trace gets printed, which
helps with debugging the deadlock.

Updates #32764

Change-Id: Icc8f5ba3ca5a485d557b7bdd76bf2f1ffb92eb3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/199537
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

1 files changed, 9 insertions, 7 deletions

diff --git a/src/runtime/lock_js.go b/src/runtime/lock_js.go
index c038499f2a..d08238ce3c 100644
--- a/src/runtime/lock_js.go
+++ b/src/runtime/lock_js.go
@@ -149,16 +149,18 @@ var returnedEventHandler *g
 func init() {
 	// At the toplevel we need an extra goroutine that handles asynchronous events.
 	initg := getg()
-	go func() {
-		returnedEventHandler = getg()
-		goready(initg, 1)
+	go handleAsyncEvents(initg)
+	gopark(nil, nil, waitReasonZero, traceEvNone, 1)
+}
 
-		gopark(nil, nil, waitReasonZero, traceEvNone, 1)
-		returnedEventHandler = nil
+func handleAsyncEvents(initg *g) {
+	returnedEventHandler = getg()
+	goready(initg, 1)
 
-		pause(getcallersp() - 16)
-	}()
 	gopark(nil, nil, waitReasonZero, traceEvNone, 1)
+	returnedEventHandler = nil
+
+	pause(getcallersp() - 16)
 }
 
 // beforeIdle gets called by the scheduler if no goroutine is awake.