sync/atomic: amend comments for Value.{Swap,CompareAndSwap}

Related to CL 241661, CL 403094.

Change-Id: I86877d9a013b05b1a97f9aa1333cd96ce98469cb
GitHub-Last-Rev: 7fedca5
GitHub-Pull-Request: #76259
Reviewed-on: https://go-review.googlesource.com/c/go/+/719660
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Keith Randall <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Junyang Shao <[email protected]>

Author: callthingsoff

src/sync/atomic/value.go

@@ -98,8 +98,7 @@ func (v *Value) Swap(new any) (old any) {
 		if typ == nil {
 			// Attempt to start first store.
 			// Disable preemption so that other goroutines can use
-			// active spin wait to wait for completion; and so that
-			// GC does not see the fake type accidentally.
+			// active spin wait to wait for completion.
 			runtime_procPin()
 			if !CompareAndSwapPointer(&vp.typ, nil, unsafe.Pointer(&firstStoreInProgress)) {
 				runtime_procUnpin()
@@ -150,8 +149,7 @@ func (v *Value) CompareAndSwap(old, new any) (swapped bool) {
 			}
 			// Attempt to start first store.
 			// Disable preemption so that other goroutines can use
-			// active spin wait to wait for completion; and so that
-			// GC does not see the fake type accidentally.
+			// active spin wait to wait for completion.
 			runtime_procPin()
 			if !CompareAndSwapPointer(&vp.typ, nil, unsafe.Pointer(&firstStoreInProgress)) {
 				runtime_procUnpin()