runtime, time: remove old timer code

Updates #6239
Updates #27707

Change-Id: I65e6471829c9de4677d3ac78ef6cd7aa0a1fc4cb
Reviewed-on: https://go-review.googlesource.com/c/go/+/171884Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

src/runtime/proc.go

@@ -4410,26 +4410,6 @@ func checkdead() {
 	}
 
 	// Maybe jump time forward for playground.
-	if oldTimers {
-		gp := timejumpOld()
-		if gp != nil {
-			casgstatus(gp, _Gwaiting, _Grunnable)
-			globrunqput(gp)
-			_p_ := pidleget()
-			if _p_ == nil {
-				throw("checkdead: no p for timer")
-			}
-			mp := mget()
-			if mp == nil {
-				// There should always be a free M since
-				// nothing is running.
-				throw("checkdead: no m for timer")
-			}
-			mp.nextp.set(_p_)
-			notewakeup(&mp.park)
-			return
-		}
-	} else {
 	_p_ := timejump()
 	if _p_ != nil {
 		for pp := &sched.pidle; *pp != 0; pp = &(*pp).ptr().link {
@@ -4448,7 +4428,6 @@ func checkdead() {
 		notewakeup(&mp.park)
 		return
 	}
-	}
 
 	// There are no goroutines running, so we can look at the P's.
 	for _, _p_ := range allp {

src/runtime/trace.go

@@ -54,7 +54,7 @@ const (
 	traceEvGoInSyscall       = 32 // denotes that goroutine is in syscall when tracing starts [timestamp, goroutine id]
 	traceEvHeapAlloc         = 33 // memstats.heap_live change [timestamp, heap_alloc]
 	traceEvNextGC            = 34 // memstats.next_gc change [timestamp, next_gc]
-	traceEvTimerGoroutine    = 35 // denotes timer goroutine [timer goroutine id]
+	traceEvTimerGoroutine    = 35 // not currently used; previously denoted timer goroutine [timer goroutine id]
 	traceEvFutileWakeup      = 36 // denotes that the previous wakeup of this goroutine was futile [timestamp]
 	traceEvString            = 37 // string dictionary entry [ID, length, string]
 	traceEvGoStartLocal      = 38 // goroutine starts running on the same P as the last event [timestamp, goroutine id]
@@ -416,13 +416,6 @@ func ReadTrace() []byte {
 		var data []byte
 		data = append(data, traceEvFrequency|0<<traceArgCountShift)
 		data = traceAppend(data, uint64(freq))
-		for i := range timers {
-			tb := &timers[i]
-			if tb.gp != nil {
-				data = append(data, traceEvTimerGoroutine|0<<traceArgCountShift)
-				data = traceAppend(data, uint64(tb.gp.goid))
-			}
-		}
 		// This will emit a bunch of full buffers, we will pick them up
 		// on the next iteration.
 		trace.stackTab.dump()

src/time/sleep.go

@@ -11,10 +11,7 @@ func Sleep(d Duration)
 // Interface to timers implemented in package runtime.
 // Must be in sync with ../runtime/time.go:/^type timer
 type runtimeTimer struct {
-	tb uintptr
-	i  int
 	pp       uintptr
-
 	when     int64
 	period   int64
 	f        func(interface{}, uintptr) // NOTE: must not be closure