runtime: clarify stack traces for bubbled goroutines

Use the synctest bubble ID to identify bubbles in traces,
rather than the goroutine ID of the bubble's root goroutine.

Some waitReasons include a "(synctest)" suffix to distinguish
a durably blocking state from a non-durable one. For example,
"chan send" vs. "chan send (synctest)". Change this suffix
to "(durable)".

Always print a "(durable)" sufix for the state of durably
blocked bubbled goroutines. For example, print "sleep (durable)".

Drop the "[not] durably blocked" text from goroutine states,
since this is now entirely redundant with the waitReason.

Old:
  goroutine 8 [chan receive (synctest), synctest bubble 7, durably blocked]:
  goroutine 9 [select (no cases), synctest bubble 7, durably blocked]:

New:
  goroutine 8 [chan receive (durable), synctest bubble 1]:
  goroutine 9 [select (no cases) (durable), synctest bubble 1]:

Change-Id: I89112efb25150a98a2954f54d1910ccec52a5824
Reviewed-on: https://go-review.googlesource.com/c/go/+/679376
Auto-Submit: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

2 files changed, 22 insertions, 19 deletions

diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 589642efc6..d1b31be172 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -1093,10 +1093,10 @@ const (
 	waitReasonGCWeakToStrongWait                      // "GC weak to strong wait"
 	waitReasonSynctestRun                             // "synctest.Run"
 	waitReasonSynctestWait                            // "synctest.Wait"
-	waitReasonSynctestChanReceive                     // "chan receive (synctest)"
-	waitReasonSynctestChanSend                        // "chan send (synctest)"
-	waitReasonSynctestSelect                          // "select (synctest)"
-	waitReasonSynctestWaitGroupWait                   // "sync.WaitGroup.Wait (synctest)"
+	waitReasonSynctestChanReceive                     // "chan receive (durable)"
+	waitReasonSynctestChanSend                        // "chan send (durable)"
+	waitReasonSynctestSelect                          // "select (durable)"
+	waitReasonSynctestWaitGroupWait                   // "sync.WaitGroup.Wait (durable)"
 	waitReasonCleanupWait                             // "cleanup wait"
 )
 
@@ -1143,10 +1143,10 @@ var waitReasonStrings = [...]string{
 	waitReasonGCWeakToStrongWait:    "GC weak to strong wait",
 	waitReasonSynctestRun:           "synctest.Run",
 	waitReasonSynctestWait:          "synctest.Wait",
-	waitReasonSynctestChanReceive:   "chan receive (synctest)",
-	waitReasonSynctestChanSend:      "chan send (synctest)",
-	waitReasonSynctestSelect:        "select (synctest)",
-	waitReasonSynctestWaitGroupWait: "sync.WaitGroup.Wait (synctest)",
+	waitReasonSynctestChanReceive:   "chan receive (durable)",
+	waitReasonSynctestChanSend:      "chan send (durable)",
+	waitReasonSynctestSelect:        "select (durable)",
+	waitReasonSynctestWaitGroupWait: "sync.WaitGroup.Wait (durable)",
 	waitReasonCleanupWait:           "cleanup wait",
 }
 
@@ -1207,12 +1207,12 @@ var isIdleInSynctest = [len(waitReasonStrings)]bool{
 }
 
 var (
-	allm           *m
-	gomaxprocs     int32
-	numCPUStartup  int32
-	forcegc        forcegcstate
-	sched          schedt
-	newprocs       int32
+	allm          *m
+	gomaxprocs    int32
+	numCPUStartup int32
+	forcegc       forcegcstate
+	sched         schedt
+	newprocs      int32
 )
 
 var (
diff --git a/src/runtime/traceback.go b/src/runtime/traceback.go
index b3baa3b4ed..00c0f08e55 100644
--- a/src/runtime/traceback.go
+++ b/src/runtime/traceback.go
@@ -1248,6 +1248,13 @@ func goroutineheader(gp *g) {
 	if isScan {
 		print(" (scan)")
 	}
+	if bubble := gp.bubble; bubble != nil &&
+		gp.waitreason.isIdleInSynctest() &&
+		!stringslite.HasSuffix(status, "(durable)") {
+		// If this isn't a status where the name includes a (durable)
+		// suffix to distinguish it from the non-durable form, add it here.
+		print(" (durable)")
+	}
 	if waitfor >= 1 {
 		print(", ", waitfor, " minutes")
 	}
@@ -1255,11 +1262,7 @@ func goroutineheader(gp *g) {
 		print(", locked to thread")
 	}
 	if bubble := gp.bubble; bubble != nil {
-		print(", synctest bubble ", bubble.root.goid, ", ")
-		if !gp.waitreason.isIdleInSynctest() {
-			print("not ")
-		}
-		print("durably blocked")
+		print(", synctest bubble ", bubble.id)
 	}
 	print("]:\n")
 }