runtime: eliminate unused _Genqueue state

_Genqueue and _Gscanenqueue were introduced as part of the GC quiesce
code. The quiesce code was removed by 197aa9e, but these states and
some associated code stuck around. Remove them.

Change-Id: I69df81881602d4a431556513dac2959668d27c20
Reviewed-on: https://go-review.googlesource.com/19638
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/proc.go

@@ -660,10 +660,6 @@ func casfrom_Gscanstatus(gp *g, oldval, newval uint32) {
 		if newval == oldval&^_Gscan {
 			success = atomic.Cas(&gp.atomicstatus, oldval, newval)
 		}
-	case _Gscanenqueue:
-		if newval == _Gwaiting {
-			success = atomic.Cas(&gp.atomicstatus, oldval, newval)
-		}
 	}
 	if !success {
 		print("runtime: casfrom_Gscanstatus failed gp=", gp, ", oldval=", hex(oldval), ", newval=", hex(newval), "\n")
@@ -680,15 +676,12 @@ func casfrom_Gscanstatus(gp *g, oldval, newval uint32) {
 func castogscanstatus(gp *g, oldval, newval uint32) bool {
 	switch oldval {
 	case _Grunnable,
+		_Grunning,
 		_Gwaiting,
 		_Gsyscall:
 		if newval == oldval|_Gscan {
 			return atomic.Cas(&gp.atomicstatus, oldval, newval)
 		}
-	case _Grunning:
-		if newval == _Gscanrunning || newval == _Gscanenqueue {
-			return atomic.Cas(&gp.atomicstatus, oldval, newval)
-		}
 	}
 	print("runtime: castogscanstatus oldval=", hex(oldval), " newval=", hex(newval), "\n")
 	throw("castogscanstatus")
@@ -843,17 +836,6 @@ func restartg(gp *g) {
 		_Gscanwaiting,
 		_Gscansyscall:
 		casfrom_Gscanstatus(gp, s, s&^_Gscan)
-
-	// Scan is now completed.
-	// Goroutine now needs to be made runnable.
-	// We put it on the global run queue; ready blocks on the global scheduler lock.
-	case _Gscanenqueue:
-		casfrom_Gscanstatus(gp, _Gscanenqueue, _Gwaiting)
-		if gp != getg().m.curg {
-			throw("processing Gscanenqueue on wrong m")
-		}
-		dropg()
-		ready(gp, 0)
 	}
 }
 

src/runtime/runtime2.go

@@ -26,7 +26,7 @@ const (
 	_Gwaiting                // 4
 	_Gmoribund_unused        // 5 currently unused, but hardcoded in gdb scripts
 	_Gdead                   // 6
-	_Genqueue                // 7 Only the Gscanenqueue is used.
+	_Genqueue_unused         // 7 currently unused
 	_Gcopystack              // 8 in this state when newstack is moving the stack
 	// the following encode that the GC is scanning the stack and what to do when it is done
 	_Gscan = 0x1000 // atomicstatus&~Gscan = the non-scan state,
@@ -37,7 +37,7 @@ const (
 	_Gscanwaiting  = _Gscan + _Gwaiting  //  0x1004 When scanning completes make it Gwaiting
 	// _Gscanmoribund_unused,               //  not possible
 	// _Gscandead,                          //  not possible
-	_Gscanenqueue = _Gscan + _Genqueue //  When scanning completes make it Grunnable and put on runqueue
+	// _Gscanenqueue_unused                 //  not possible
 )
 
 const (

src/runtime/traceback.go

@@ -645,7 +645,6 @@ var gStatusStrings = [...]string{
 	_Gsyscall:   "syscall",
 	_Gwaiting:   "waiting",
 	_Gdead:      "dead",
-	_Genqueue:   "enqueue",
 	_Gcopystack: "copystack",
 }