runtime: minor updates to netpoll comments

In Go 1.4 we renamed READY to pdReady and WAIT to pdWait as part of
rewriting netpoll from C to Go. Finish updating the comments to use
the new names.

Change-Id: I6cefc698b46c58211fd6be1489bdd70419454962
Reviewed-on: https://go-review.googlesource.com/c/go/+/223998
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Author: ianlancetaylor

src/runtime/netpoll.go

@@ -39,12 +39,12 @@ import (
 //           a goroutine consumes the notification by changing the state to nil.
 // pdWait - a goroutine prepares to park on the semaphore, but not yet parked;
 //          the goroutine commits to park by changing the state to G pointer,
-//          or, alternatively, concurrent io notification changes the state to READY,
+//          or, alternatively, concurrent io notification changes the state to pdReady,
 //          or, alternatively, concurrent timeout/close changes the state to nil.
 // G pointer - the goroutine is blocked on the semaphore;
-//             io notification or timeout/close changes the state to READY or nil respectively
+//             io notification or timeout/close changes the state to pdReady or nil respectively
 //             and unparks the goroutine.
-// nil - nothing of the above.
+// nil - none of the above.
 const (
 	pdReady uintptr = 1
 	pdWait  uintptr = 2
@@ -397,7 +397,7 @@ func netpollblock(pd *pollDesc, mode int32, waitio bool) bool {
 		gpp = &pd.wg
 	}
 
-	// set the gpp semaphore to WAIT
+	// set the gpp semaphore to pdWait
 	for {
 		old := *gpp
 		if old == pdReady {
@@ -412,13 +412,13 @@ func netpollblock(pd *pollDesc, mode int32, waitio bool) bool {
 		}
 	}
 
-	// need to recheck error states after setting gpp to WAIT
+	// need to recheck error states after setting gpp to pdWait
 	// this is necessary because runtime_pollUnblock/runtime_pollSetDeadline/deadlineimpl
 	// do the opposite: store to closing/rd/wd, membarrier, load of rg/wg
 	if waitio || netpollcheckerr(pd, mode) == 0 {
 		gopark(netpollblockcommit, unsafe.Pointer(gpp), waitReasonIOWait, traceEvGoBlockNet, 5)
 	}
-	// be careful to not lose concurrent READY notification
+	// be careful to not lose concurrent pdReady notification
 	old := atomic.Xchguintptr(gpp, 0)
 	if old > pdWait {
 		throw("runtime: corrupted polldesc")
@@ -438,7 +438,7 @@ func netpollunblock(pd *pollDesc, mode int32, ioready bool) *g {
 			return nil
 		}
 		if old == 0 && !ioready {
-			// Only set READY for ioready. runtime_pollWait
+			// Only set pdReady for ioready. runtime_pollWait
 			// will check for timeout/cancel before waiting.
 			return nil
 		}