runtime: convert g.selectDone to atomic type

On the write side, g.selectDone has been converted
from non-atomic to atomic access.

For #53821.

Change-Id: Iac46bc6acce7eed51dfd990285dd57f0d58b4ae2
Reviewed-on: https://go-review.googlesource.com/c/go/+/425414
Run-TryBot: hopehook <hopehook@qq.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/runtime/chan.go

@@ -791,7 +791,7 @@ func (q *waitq) dequeue() *sudog {
 		// We use a flag in the G struct to tell us when someone
 		// else has won the race to signal this goroutine but the goroutine
 		// hasn't removed itself from the queue yet.
-		if sgp.isSelect && !atomic.Cas(&sgp.g.selectDone, 0, 1) {
+		if sgp.isSelect && !sgp.g.selectDone.CompareAndSwap(0, 1) {
 			continue
 		}
 

src/runtime/runtime2.go

@@ -487,7 +487,7 @@ type g struct {
 	cgoCtxt        []uintptr      // cgo traceback context
 	labels         unsafe.Pointer // profiler labels
 	timer          *timer         // cached timer for time.Sleep
-	selectDone     uint32         // are we participating in a select and did someone win the race?
+	selectDone     atomic.Uint32  // are we participating in a select and did someone win the race?
 
 	// goroutineProfiled indicates the status of this goroutine's stack for the
 	// current in-progress goroutine profile

src/runtime/select.go

@@ -329,7 +329,7 @@ func selectgo(cas0 *scase, order0 *uint16, pc0 *uintptr, nsends, nrecvs int, blo
 
 	sellock(scases, lockorder)
 
-	gp.selectDone = 0
+	gp.selectDone.Store(0)
 	sg = (*sudog)(gp.param)
 	gp.param = nil