runtime: make the lock rank DAG make more sense

This groups, comments, and generally reorganizes the lock rank graph
description by subsystem. It also introduces several pseudo-nodes that
more cleanly describe the inherent layering of lock ranks by
subsystem.

I believe this doesn't actually change the graph, but haven't verified
this.

For #53789.

Change-Id: I72f332f5a23b8217c7dc1b21411631ad48cee4b0
Reviewed-on: https://go-review.googlesource.com/c/go/+/418718
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

2 files changed, 214 insertions, 91 deletions

diff --git a/src/runtime/lockrank.go b/src/runtime/lockrank.go
index 21c65233e3..83d1ac3f0b 100644
--- a/src/runtime/lockrank.go
+++ b/src/runtime/lockrank.go
@@ -12,48 +12,54 @@ const (
 	lockRankUnknown lockRank = iota
 
 	lockRankSysmon
+	lockRankScavenge
+	lockRankForcegc
+	lockRankDefer
 	lockRankSweepWaiters
 	lockRankAssistQueue
-	lockRankCpuprof
 	lockRankSweep
 	lockRankPollDesc
-	lockRankDeadlock
-	lockRankItab
-	lockRankNotifyList
-	lockRankRoot
-	lockRankRwmutexW
-	lockRankDefer
-	lockRankScavenge
-	lockRankForcegc
+	lockRankCpuprof
 	lockRankSched
 	lockRankAllg
 	lockRankAllp
 	lockRankTimers
-	lockRankReflectOffs
+	lockRankNetpollInit
 	lockRankHchan
+	lockRankNotifyList
+	lockRankSudog
+	lockRankRwmutexW
+	lockRankRwmutexR
+	lockRankRoot
+	lockRankItab
+	lockRankReflectOffs
+	// TRACEGLOBAL
 	lockRankTraceBuf
 	lockRankTraceStrings
+	// MALLOC
+	lockRankFin
+	lockRankGcBitsArenas
+	lockRankMheapSpecial
 	lockRankMspanSpecial
+	lockRankSpanSetSpine
+	// MPROF
 	lockRankProfInsert
 	lockRankProfBlock
 	lockRankProfMemActive
-	lockRankGcBitsArenas
-	lockRankSpanSetSpine
-	lockRankMheapSpecial
-	lockRankFin
 	lockRankProfMemFuture
+	// TRACE
 	lockRankTrace
 	lockRankTraceStackTab
-	lockRankNetpollInit
-	lockRankRwmutexR
+	// STACKGROW
 	lockRankGscan
 	lockRankStackpool
 	lockRankStackLarge
 	lockRankHchanLeaf
-	lockRankSudog
+	// WB
 	lockRankWbufSpans
 	lockRankMheap
 	lockRankGlobalAlloc
+	lockRankDeadlock
 	lockRankPanic
 )
 
@@ -64,48 +70,48 @@ const lockRankLeafRank lockRank = 1000
 // lockNames gives the names associated with each of the above ranks.
 var lockNames = []string{
 	lockRankSysmon:        "sysmon",
+	lockRankScavenge:      "scavenge",
+	lockRankForcegc:       "forcegc",
+	lockRankDefer:         "defer",
 	lockRankSweepWaiters:  "sweepWaiters",
 	lockRankAssistQueue:   "assistQueue",
-	lockRankCpuprof:       "cpuprof",
 	lockRankSweep:         "sweep",
 	lockRankPollDesc:      "pollDesc",
-	lockRankDeadlock:      "deadlock",
-	lockRankItab:          "itab",
-	lockRankNotifyList:    "notifyList",
-	lockRankRoot:          "root",
-	lockRankRwmutexW:      "rwmutexW",
-	lockRankDefer:         "defer",
-	lockRankScavenge:      "scavenge",
-	lockRankForcegc:       "forcegc",
+	lockRankCpuprof:       "cpuprof",
 	lockRankSched:         "sched",
 	lockRankAllg:          "allg",
 	lockRankAllp:          "allp",
 	lockRankTimers:        "timers",
-	lockRankReflectOffs:   "reflectOffs",
+	lockRankNetpollInit:   "netpollInit",
 	lockRankHchan:         "hchan",
+	lockRankNotifyList:    "notifyList",
+	lockRankSudog:         "sudog",
+	lockRankRwmutexW:      "rwmutexW",
+	lockRankRwmutexR:      "rwmutexR",
+	lockRankRoot:          "root",
+	lockRankItab:          "itab",
+	lockRankReflectOffs:   "reflectOffs",
 	lockRankTraceBuf:      "traceBuf",
 	lockRankTraceStrings:  "traceStrings",
+	lockRankFin:           "fin",
+	lockRankGcBitsArenas:  "gcBitsArenas",
+	lockRankMheapSpecial:  "mheapSpecial",
 	lockRankMspanSpecial:  "mspanSpecial",
+	lockRankSpanSetSpine:  "spanSetSpine",
 	lockRankProfInsert:    "profInsert",
 	lockRankProfBlock:     "profBlock",
 	lockRankProfMemActive: "profMemActive",
-	lockRankGcBitsArenas:  "gcBitsArenas",
-	lockRankSpanSetSpine:  "spanSetSpine",
-	lockRankMheapSpecial:  "mheapSpecial",
-	lockRankFin:           "fin",
 	lockRankProfMemFuture: "profMemFuture",
 	lockRankTrace:         "trace",
 	lockRankTraceStackTab: "traceStackTab",
-	lockRankNetpollInit:   "netpollInit",
-	lockRankRwmutexR:      "rwmutexR",
 	lockRankGscan:         "gscan",
 	lockRankStackpool:     "stackpool",
 	lockRankStackLarge:    "stackLarge",
 	lockRankHchanLeaf:     "hchanLeaf",
-	lockRankSudog:         "sudog",
 	lockRankWbufSpans:     "wbufSpans",
 	lockRankMheap:         "mheap",
 	lockRankGlobalAlloc:   "globalAlloc",
+	lockRankDeadlock:      "deadlock",
 	lockRankPanic:         "panic",
 }
 
@@ -129,47 +135,47 @@ func (rank lockRank) String() string {
 // Lock ranks that allow self-cycles list themselves.
 var lockPartialOrder [][]lockRank = [][]lockRank{
 	lockRankSysmon:        {},
+	lockRankScavenge:      {lockRankSysmon},
+	lockRankForcegc:       {lockRankSysmon},
+	lockRankDefer:         {},
 	lockRankSweepWaiters:  {},
 	lockRankAssistQueue:   {},
-	lockRankCpuprof:       {},
 	lockRankSweep:         {},
 	lockRankPollDesc:      {},
-	lockRankDeadlock:      {},
-	lockRankItab:          {},
+	lockRankCpuprof:       {},
+	lockRankSched:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof},
+	lockRankAllg:          {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched},
+	lockRankAllp:          {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched},
+	lockRankTimers:        {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllp, lockRankTimers},
+	lockRankNetpollInit:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllp, lockRankTimers},
+	lockRankHchan:         {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankHchan},
 	lockRankNotifyList:    {},
-	lockRankRoot:          {},
+	lockRankSudog:         {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankHchan, lockRankNotifyList},
 	lockRankRwmutexW:      {},
-	lockRankDefer:         {},
-	lockRankScavenge:      {lockRankSysmon},
-	lockRankForcegc:       {lockRankSysmon},
-	lockRankSched:         {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankScavenge, lockRankForcegc},
-	lockRankAllg:          {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankScavenge, lockRankForcegc, lockRankSched},
-	lockRankAllp:          {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankScavenge, lockRankForcegc, lockRankSched},
-	lockRankTimers:        {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllp, lockRankTimers},
+	lockRankRwmutexR:      {lockRankSysmon, lockRankRwmutexW},
+	lockRankRoot:          {},
+	lockRankItab:          {},
 	lockRankReflectOffs:   {lockRankItab},
-	lockRankHchan:         {lockRankSysmon, lockRankSweep, lockRankScavenge, lockRankHchan},
 	lockRankTraceBuf:      {lockRankSysmon, lockRankScavenge},
 	lockRankTraceStrings:  {lockRankSysmon, lockRankScavenge, lockRankTraceBuf},
-	lockRankMspanSpecial:  {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankProfInsert:    {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankProfBlock:     {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankProfMemActive: {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankGcBitsArenas:  {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankSpanSetSpine:  {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankMheapSpecial:  {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankFin:           {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankProfMemFuture: {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings, lockRankProfMemActive},
-	lockRankTrace:         {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankRoot, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings, lockRankFin},
-	lockRankTraceStackTab: {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankRoot, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankTrace},
-	lockRankNetpollInit:   {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllp, lockRankTimers},
-	lockRankRwmutexR:      {lockRankSysmon, lockRankRwmutexW},
-	lockRankGscan:         {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankRoot, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankGcBitsArenas, lockRankSpanSetSpine, lockRankFin, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankNetpollInit},
-	lockRankStackpool:     {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankRoot, lockRankRwmutexW, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankGcBitsArenas, lockRankSpanSetSpine, lockRankFin, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankNetpollInit, lockRankRwmutexR, lockRankGscan},
-	lockRankStackLarge:    {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankRoot, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankGcBitsArenas, lockRankSpanSetSpine, lockRankFin, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankNetpollInit, lockRankGscan},
-	lockRankHchanLeaf:     {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankRoot, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankGcBitsArenas, lockRankSpanSetSpine, lockRankFin, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankNetpollInit, lockRankGscan, lockRankHchanLeaf},
-	lockRankSudog:         {lockRankSysmon, lockRankSweep, lockRankNotifyList, lockRankScavenge, lockRankHchan},
-	lockRankWbufSpans:     {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankRoot, lockRankDefer, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings, lockRankMspanSpecial, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankGcBitsArenas, lockRankSpanSetSpine, lockRankFin, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankNetpollInit, lockRankGscan, lockRankSudog},
-	lockRankMheap:         {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankRoot, lockRankRwmutexW, lockRankDefer, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings, lockRankMspanSpecial, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankGcBitsArenas, lockRankSpanSetSpine, lockRankFin, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankNetpollInit, lockRankRwmutexR, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankSudog, lockRankWbufSpans},
-	lockRankGlobalAlloc:   {lockRankSysmon, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankItab, lockRankNotifyList, lockRankRoot, lockRankRwmutexW, lockRankDefer, lockRankScavenge, lockRankForcegc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings, lockRankMspanSpecial, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankGcBitsArenas, lockRankSpanSetSpine, lockRankMheapSpecial, lockRankFin, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankNetpollInit, lockRankRwmutexR, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankSudog, lockRankWbufSpans, lockRankMheap},
+	lockRankFin:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankGcBitsArenas:  {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankMheapSpecial:  {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankMspanSpecial:  {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankSpanSetSpine:  {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankProfInsert:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankProfBlock:     {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankProfMemActive: {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankProfMemFuture: {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankProfMemActive},
+	lockRankTrace:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin},
+	lockRankTraceStackTab: {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankTrace},
+	lockRankGscan:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab},
+	lockRankStackpool:     {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRwmutexW, lockRankRwmutexR, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankGscan},
+	lockRankStackLarge:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankGscan},
+	lockRankHchanLeaf:     {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankGscan, lockRankHchanLeaf},
+	lockRankWbufSpans:     {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankMspanSpecial, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankGscan},
+	lockRankMheap:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRwmutexW, lockRankRwmutexR, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankMspanSpecial, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans},
+	lockRankGlobalAlloc:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRwmutexW, lockRankRwmutexR, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankGcBitsArenas, lockRankMheapSpecial, lockRankMspanSpecial, lockRankSpanSetSpine, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankTrace, lockRankTraceStackTab, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap},
+	lockRankDeadlock:      {},
 	lockRankPanic:         {lockRankDeadlock},
 }
diff --git a/src/runtime/mklockrank.go b/src/runtime/mklockrank.go
index d0b882415c..fc7c0223e4 100644
--- a/src/runtime/mklockrank.go
+++ b/src/runtime/mklockrank.go
@@ -32,42 +32,144 @@ import (
 // lock, which means no other lock can be acquired while it is held.
 // Therefore, leaf locks do not need to be given an explicit rank.
 //
+// Ranks in all caps are pseudo-nodes that help define order, but do
+// not actually define a rank.
+//
 // TODO: It's often hard to correlate rank names to locks. Change
 // these to be more consistent with the locks they label.
 const ranks = `
-NONE < sysmon, sweepWaiters, assistQueue, cpuprof, sweep, pollDesc, deadlock, itab, notifyList, root, rwmutexW, defer;
-sysmon < scavenge, forcegc;
-assistQueue, cpuprof, forcegc, pollDesc, scavenge, sweep, sweepWaiters < sched;
+# Sysmon
+NONE
+< sysmon
+< scavenge, forcegc;
+
+# Defer
+NONE < defer;
+
+# GC
+NONE <
+  sweepWaiters,
+  assistQueue,
+  sweep;
+
+# Scheduler, timers, netpoll
+NONE < pollDesc, cpuprof;
+assistQueue,
+  cpuprof,
+  forcegc,
+  pollDesc, # pollDesc can interact with timers, which can lock sched.
+  scavenge,
+  sweep,
+  sweepWaiters
+< sched;
 sched < allg, allp;
 allp < timers;
-itab < reflectOffs;
+timers < netpollInit;
+
+# Channels
 scavenge, sweep < hchan;
-scavenge < traceBuf;
+NONE < notifyList;
+hchan, notifyList < sudog;
+
+# RWMutex
+NONE < rwmutexW;
+rwmutexW, sysmon < rwmutexR;
+
+# Semaphores
+NONE < root;
+
+# Itabs
+NONE
+< itab
+< reflectOffs;
+
+# Tracing without a P uses a global trace buffer.
+scavenge
+# Above TRACEGLOBAL can emit a trace event without a P.
+< TRACEGLOBAL
+# Below TRACEGLOBAL manages the global tracing buffer.
+# Note that traceBuf eventually chains to MALLOC, but we never get that far
+# in the situation where there's no P.
+< traceBuf;
+# Starting/stopping tracing traces strings.
 traceBuf < traceStrings;
-allg, hchan, notifyList, reflectOffs, timers, traceStrings < mspanSpecial, profInsert, profBlock, profMemActive, gcBitsArenas, spanSetSpine, mheapSpecial, fin;
+
+# Malloc
+allg,
+  hchan,
+  notifyList,
+  reflectOffs,
+  timers,
+  traceStrings
+# Above MALLOC are things that can allocate memory.
+< MALLOC
+# Below MALLOC is the malloc implementation.
+< fin,
+  gcBitsArenas,
+  mheapSpecial,
+  mspanSpecial,
+  spanSetSpine,
+  MPROF;
+
+# Memory profiling
+MPROF < profInsert, profBlock, profMemActive;
 profMemActive < profMemFuture;
-hchan, root, sched, traceStrings, notifyList, fin < trace;
-trace < traceStackTab;
-timers < netpollInit;
-rwmutexW, sysmon < rwmutexR;
-gcBitsArenas, netpollInit, profBlock, profInsert, profMemFuture, spanSetSpine, traceStackTab < gscan;
+
+# Execution tracer events (with a P)
+hchan,
+  root,
+  sched,
+  traceStrings,
+  notifyList,
+  fin
+# Above TRACE is anything that can create a trace event
+< TRACE
+< trace
+< traceStackTab;
+
+# Stack allocation and copying
+gcBitsArenas,
+  netpollInit,
+  profBlock,
+  profInsert,
+  profMemFuture,
+  spanSetSpine,
+  traceStackTab
+# Anything that can grow the stack can acquire STACKGROW.
+# (Most higher layers imply STACKGROW, like MALLOC.)
+< STACKGROW
+# Below STACKGROW is the stack allocator/copying implementation.
+< gscan;
 gscan, rwmutexR < stackpool;
 gscan < stackLarge;
-
-# Generally, hchan must be acquired before gscan. But in one specific
-# case (in syncadjustsudogs from markroot after the g has been suspended
-# by suspendG), we allow gscan to be acquired, and then an hchan lock. To
-# allow this case, we use this hchanLeaf rank in syncadjustsudogs(),
-# rather than hchan. By using this special rank, we don't allow any further
-# locks to be acquired other than more hchan locks.
+# Generally, hchan must be acquired before gscan. But in one case,
+# where we suspend a G and then shrink its stack, syncadjustsudogs
+# can acquire hchan locks while holding gscan. To allow this case,
+# we use hchanLeaf instead of hchan.
 gscan < hchanLeaf;
 
-hchan, notifyList < sudog;
-defer, gscan, mspanSpecial, sudog < wbufSpans;
-stackLarge, stackpool, wbufSpans < mheap;
+# Write barrier
+defer,
+  gscan,
+  mspanSpecial,
+  sudog
+# Anything that can have write barriers can acquire WB.
+# Above WB, we can have write barriers.
+< WB
+# Below WB is the write barrier implementation.
+< wbufSpans;
+
+# Span allocator
+stackLarge,
+  stackpool,
+  wbufSpans
+# Above mheap is anything that can call the span allocator.
+< mheap;
+# Below mheap is the span allocator implementation.
 mheap, mheapSpecial < globalAlloc;
 
 # panic is handled specially. It is implicitly below all other locks.
+NONE < deadlock;
 deadlock < panic;
 `
 
@@ -158,7 +260,11 @@ const (
 
 `)
 	for _, rank := range topo {
-		fmt.Fprintf(w, "\t%s\n", cname(rank))
+		if isPseudo(rank) {
+			fmt.Fprintf(w, "\t// %s\n", rank)
+		} else {
+			fmt.Fprintf(w, "\t%s\n", cname(rank))
+		}
 	}
 	fmt.Fprintf(w, `)
 
@@ -173,7 +279,9 @@ const lockRankLeafRank lockRank = 1000
 var lockNames = []string{
 `)
 	for _, rank := range topo {
-		fmt.Fprintf(w, "\t%s: %q,\n", cname(rank), rank)
+		if !isPseudo(rank) {
+			fmt.Fprintf(w, "\t%s: %q,\n", cname(rank), rank)
+		}
 	}
 	fmt.Fprintf(w, `}
 
@@ -201,9 +309,14 @@ func (rank lockRank) String() string {
 var lockPartialOrder [][]lockRank = [][]lockRank{
 `)
 	for _, rank := range topo {
+		if isPseudo(rank) {
+			continue
+		}
 		list := []string{}
 		for _, before := range g.Edges(rank) {
-			list = append(list, cname(before))
+			if !isPseudo(before) {
+				list = append(list, cname(before))
+			}
 		}
 		if cyclicRanks[rank] {
 			list = append(list, cname(rank))
@@ -219,6 +332,10 @@ func cname(label string) string {
 	return "lockRank" + strings.ToUpper(label[:1]) + label[1:]
 }
 
+func isPseudo(label string) bool {
+	return strings.ToUpper(label) == label
+}
+
 // generateDot emits a Graphviz dot representation of g to w.
 func generateDot(w io.Writer, g *dag.Graph) {
 	fmt.Fprintf(w, "digraph g {\n")