runtime: convert schedt.goidgen to atomic type

For #53821.

Change-Id: I84c96ade5982b8e68d1d1787bf1bfa16a17a4fb4
Reviewed-on: https://go-review.googlesource.com/c/go/+/419439
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/runtime/align_runtime_test.go

@@ -17,7 +17,6 @@ var AtomicFields = []uintptr{
 	unsafe.Offsetof(p{}.timer0When),
 	unsafe.Offsetof(p{}.timerModifiedEarliest),
 	unsafe.Offsetof(p{}.gcFractionalMarkTime),
-	unsafe.Offsetof(schedt{}.goidgen),
 	unsafe.Offsetof(schedt{}.lastpoll),
 	unsafe.Offsetof(schedt{}.pollUntil),
 	unsafe.Offsetof(schedt{}.timeToRun),

src/runtime/proc.go

@@ -1919,7 +1919,7 @@ func oneNewExtraM() {
 	mp.lockedInt++
 	mp.lockedg.set(gp)
 	gp.lockedm.set(mp)
-	gp.goid = int64(atomic.Xadd64(&sched.goidgen, 1))
+	gp.goid = int64(sched.goidgen.Add(1))
 	if raceenabled {
 		gp.racectx = racegostart(abi.FuncPCABIInternal(newextram) + sys.PCQuantum)
 	}
@@ -4168,7 +4168,7 @@ func newproc1(fn *funcval, callergp *g, callerpc uintptr) *g {
 		// Sched.goidgen is the last allocated id,
 		// this batch must be [sched.goidgen+1, sched.goidgen+GoidCacheBatch].
 		// At startup sched.goidgen=0, so main goroutine receives goid=1.
-		pp.goidcache = atomic.Xadd64(&sched.goidgen, _GoidCacheBatch)
+		pp.goidcache = sched.goidgen.Add(_GoidCacheBatch)
 		pp.goidcache -= _GoidCacheBatch - 1
 		pp.goidcacheend = pp.goidcache + _GoidCacheBatch
 	}

src/runtime/runtime2.go

@@ -759,7 +759,7 @@ type p struct {
 
 type schedt struct {
 	// accessed atomically. keep at top to ensure alignment on 32-bit systems.
-	goidgen   uint64
+	goidgen   atomic.Uint64
 	lastpoll  uint64 // time of last network poll, 0 if currently polling
 	pollUntil uint64 // time to which current poll is sleeping