runtime: replace rwmutexR/W with per-rwmutex lock rank

CL 549536 intended to decouple the internal implementation of rwmutex
from the semantic meaning of an rwmutex read/write lock in the static
lock ranking.

Unfortunately, it was not thought through well enough. The internals
were represented with the rwmutexR and rwmutexW lock ranks. The idea was
that the internal lock ranks need not model the higher-level ordering,
since those have separate rankings. That is incorrect; rwmutexW is held
for the duration of a write lock, so it must be ranked before any lock
taken while any write lock is held, which is precisely what we were
trying to avoid.

This is visible in violations like:

        0 : execW 11 0x0
        1 : rwmutexW 51 0x111d9c8
        2 : fin 30 0x111d3a0
        fatal error: lock ordering problem

execW < fin is modeled, but rwmutexW < fin is missing.

Fix this by eliminating the rwmutexR/W lock ranks shared across
different types of rwmutex. Instead require users to define an
additional "internal" lock rank to represent the implementation details
of rwmutex.rLock. We can avoid an additional "internal" lock rank for
rwmutex.wLock because the existing writeRank has the same semantics for
semantic and internal locking. i.e., writeRank is held for the duration
of a write lock, which is exactly how rwmutex.wLock is used, so we can
use writeRank directly on wLock.

For #64722.

Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-staticlockranking
Change-Id: Ia572de188a46ba8fe054ae28537648beaa16b12c
Reviewed-on: https://go-review.googlesource.com/c/go/+/555055
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

5 files changed, 143 insertions, 134 deletions

diff --git a/src/runtime/export_test.go b/src/runtime/export_test.go
index 11e4bd26c5..e25f748ed4 100644
--- a/src/runtime/export_test.go
+++ b/src/runtime/export_test.go
@@ -587,7 +587,7 @@ type RWMutex struct {
 }
 
 func (rw *RWMutex) Init() {
-	rw.rw.init(lockRankTestR, lockRankTestW)
+	rw.rw.init(lockRankTestR, lockRankTestRInternal, lockRankTestW)
 }
 
 func (rw *RWMutex) RLock() {
diff --git a/src/runtime/lockrank.go b/src/runtime/lockrank.go
index 43b3239f1e..b27e6c5606 100644
--- a/src/runtime/lockrank.go
+++ b/src/runtime/lockrank.go
@@ -69,8 +69,9 @@ const (
 	lockRankPanic
 	lockRankDeadlock
 	lockRankRaceFini
-	lockRankRwmutexW
-	lockRankRwmutexR
+	lockRankAllocmRInternal
+	lockRankExecRInternal
+	lockRankTestRInternal
 )
 
 // lockRankLeafRank is the rank of lock that does not have a declared rank,
@@ -79,59 +80,60 @@ 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",
-	lockRankSweep:          "sweep",
-	lockRankTestR:          "testR",
-	lockRankTestW:          "testW",
-	lockRankAllocmW:        "allocmW",
-	lockRankExecW:          "execW",
-	lockRankCpuprof:        "cpuprof",
-	lockRankPollDesc:       "pollDesc",
-	lockRankWakeableSleep:  "wakeableSleep",
-	lockRankAllocmR:        "allocmR",
-	lockRankExecR:          "execR",
-	lockRankSched:          "sched",
-	lockRankAllg:           "allg",
-	lockRankAllp:           "allp",
-	lockRankTimers:         "timers",
-	lockRankNetpollInit:    "netpollInit",
-	lockRankHchan:          "hchan",
-	lockRankNotifyList:     "notifyList",
-	lockRankSudog:          "sudog",
-	lockRankRoot:           "root",
-	lockRankItab:           "itab",
-	lockRankReflectOffs:    "reflectOffs",
-	lockRankUserArenaState: "userArenaState",
-	lockRankTraceBuf:       "traceBuf",
-	lockRankTraceStrings:   "traceStrings",
-	lockRankFin:            "fin",
-	lockRankSpanSetSpine:   "spanSetSpine",
-	lockRankMspanSpecial:   "mspanSpecial",
-	lockRankGcBitsArenas:   "gcBitsArenas",
-	lockRankProfInsert:     "profInsert",
-	lockRankProfBlock:      "profBlock",
-	lockRankProfMemActive:  "profMemActive",
-	lockRankProfMemFuture:  "profMemFuture",
-	lockRankGscan:          "gscan",
-	lockRankStackpool:      "stackpool",
-	lockRankStackLarge:     "stackLarge",
-	lockRankHchanLeaf:      "hchanLeaf",
-	lockRankWbufSpans:      "wbufSpans",
-	lockRankMheap:          "mheap",
-	lockRankMheapSpecial:   "mheapSpecial",
-	lockRankGlobalAlloc:    "globalAlloc",
-	lockRankTrace:          "trace",
-	lockRankTraceStackTab:  "traceStackTab",
-	lockRankPanic:          "panic",
-	lockRankDeadlock:       "deadlock",
-	lockRankRaceFini:       "raceFini",
-	lockRankRwmutexW:       "rwmutexW",
-	lockRankRwmutexR:       "rwmutexR",
+	lockRankSysmon:          "sysmon",
+	lockRankScavenge:        "scavenge",
+	lockRankForcegc:         "forcegc",
+	lockRankDefer:           "defer",
+	lockRankSweepWaiters:    "sweepWaiters",
+	lockRankAssistQueue:     "assistQueue",
+	lockRankSweep:           "sweep",
+	lockRankTestR:           "testR",
+	lockRankTestW:           "testW",
+	lockRankAllocmW:         "allocmW",
+	lockRankExecW:           "execW",
+	lockRankCpuprof:         "cpuprof",
+	lockRankPollDesc:        "pollDesc",
+	lockRankWakeableSleep:   "wakeableSleep",
+	lockRankAllocmR:         "allocmR",
+	lockRankExecR:           "execR",
+	lockRankSched:           "sched",
+	lockRankAllg:            "allg",
+	lockRankAllp:            "allp",
+	lockRankTimers:          "timers",
+	lockRankNetpollInit:     "netpollInit",
+	lockRankHchan:           "hchan",
+	lockRankNotifyList:      "notifyList",
+	lockRankSudog:           "sudog",
+	lockRankRoot:            "root",
+	lockRankItab:            "itab",
+	lockRankReflectOffs:     "reflectOffs",
+	lockRankUserArenaState:  "userArenaState",
+	lockRankTraceBuf:        "traceBuf",
+	lockRankTraceStrings:    "traceStrings",
+	lockRankFin:             "fin",
+	lockRankSpanSetSpine:    "spanSetSpine",
+	lockRankMspanSpecial:    "mspanSpecial",
+	lockRankGcBitsArenas:    "gcBitsArenas",
+	lockRankProfInsert:      "profInsert",
+	lockRankProfBlock:       "profBlock",
+	lockRankProfMemActive:   "profMemActive",
+	lockRankProfMemFuture:   "profMemFuture",
+	lockRankGscan:           "gscan",
+	lockRankStackpool:       "stackpool",
+	lockRankStackLarge:      "stackLarge",
+	lockRankHchanLeaf:       "hchanLeaf",
+	lockRankWbufSpans:       "wbufSpans",
+	lockRankMheap:           "mheap",
+	lockRankMheapSpecial:    "mheapSpecial",
+	lockRankGlobalAlloc:     "globalAlloc",
+	lockRankTrace:           "trace",
+	lockRankTraceStackTab:   "traceStackTab",
+	lockRankPanic:           "panic",
+	lockRankDeadlock:        "deadlock",
+	lockRankRaceFini:        "raceFini",
+	lockRankAllocmRInternal: "allocmRInternal",
+	lockRankExecRInternal:   "execRInternal",
+	lockRankTestRInternal:   "testRInternal",
 }
 
 func (rank lockRank) String() string {
@@ -153,57 +155,58 @@ 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:    {},
-	lockRankSweep:          {},
-	lockRankTestR:          {},
-	lockRankTestW:          {},
-	lockRankAllocmW:        {},
-	lockRankExecW:          {},
-	lockRankCpuprof:        {},
-	lockRankPollDesc:       {},
-	lockRankWakeableSleep:  {},
-	lockRankAllocmR:        {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep},
-	lockRankExecR:          {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep},
-	lockRankSched:          {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR},
-	lockRankAllg:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched},
-	lockRankAllp:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched},
-	lockRankTimers:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllp, lockRankTimers},
-	lockRankNetpollInit:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllp, lockRankTimers},
-	lockRankHchan:          {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankWakeableSleep, lockRankHchan},
-	lockRankNotifyList:     {},
-	lockRankSudog:          {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankWakeableSleep, lockRankHchan, lockRankNotifyList},
-	lockRankRoot:           {},
-	lockRankItab:           {},
-	lockRankReflectOffs:    {lockRankItab},
-	lockRankUserArenaState: {},
-	lockRankTraceBuf:       {lockRankSysmon, lockRankScavenge},
-	lockRankTraceStrings:   {lockRankSysmon, lockRankScavenge, lockRankTraceBuf},
-	lockRankFin:            {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankSpanSetSpine:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankMspanSpecial:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankGcBitsArenas:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankMspanSpecial},
-	lockRankProfInsert:     {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankProfBlock:      {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankProfMemActive:  {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
-	lockRankProfMemFuture:  {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankProfMemActive},
-	lockRankGscan:          {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture},
-	lockRankStackpool:      {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
-	lockRankStackLarge:     {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
-	lockRankHchanLeaf:      {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankHchanLeaf},
-	lockRankWbufSpans:      {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
-	lockRankMheap:          {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans},
-	lockRankMheapSpecial:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap},
-	lockRankGlobalAlloc:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap, lockRankMheapSpecial},
-	lockRankTrace:          {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap},
-	lockRankTraceStackTab:  {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap, lockRankTrace},
-	lockRankPanic:          {},
-	lockRankDeadlock:       {lockRankPanic, lockRankDeadlock},
-	lockRankRaceFini:       {lockRankPanic},
-	lockRankRwmutexW:       {lockRankTestW, lockRankAllocmW, lockRankExecW},
-	lockRankRwmutexR:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankTestW, lockRankAllocmW, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankRwmutexW},
+	lockRankSysmon:          {},
+	lockRankScavenge:        {lockRankSysmon},
+	lockRankForcegc:         {lockRankSysmon},
+	lockRankDefer:           {},
+	lockRankSweepWaiters:    {},
+	lockRankAssistQueue:     {},
+	lockRankSweep:           {},
+	lockRankTestR:           {},
+	lockRankTestW:           {},
+	lockRankAllocmW:         {},
+	lockRankExecW:           {},
+	lockRankCpuprof:         {},
+	lockRankPollDesc:        {},
+	lockRankWakeableSleep:   {},
+	lockRankAllocmR:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep},
+	lockRankExecR:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep},
+	lockRankSched:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR},
+	lockRankAllg:            {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched},
+	lockRankAllp:            {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched},
+	lockRankTimers:          {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllp, lockRankTimers},
+	lockRankNetpollInit:     {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllp, lockRankTimers},
+	lockRankHchan:           {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankWakeableSleep, lockRankHchan},
+	lockRankNotifyList:      {},
+	lockRankSudog:           {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankWakeableSleep, lockRankHchan, lockRankNotifyList},
+	lockRankRoot:            {},
+	lockRankItab:            {},
+	lockRankReflectOffs:     {lockRankItab},
+	lockRankUserArenaState:  {},
+	lockRankTraceBuf:        {lockRankSysmon, lockRankScavenge},
+	lockRankTraceStrings:    {lockRankSysmon, lockRankScavenge, lockRankTraceBuf},
+	lockRankFin:             {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankSpanSetSpine:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankMspanSpecial:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankGcBitsArenas:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankMspanSpecial},
+	lockRankProfInsert:      {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankProfBlock:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankProfMemActive:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings},
+	lockRankProfMemFuture:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankHchan, lockRankNotifyList, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankProfMemActive},
+	lockRankGscan:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture},
+	lockRankStackpool:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
+	lockRankStackLarge:      {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
+	lockRankHchanLeaf:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankHchanLeaf},
+	lockRankWbufSpans:       {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan},
+	lockRankMheap:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans},
+	lockRankMheapSpecial:    {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap},
+	lockRankGlobalAlloc:     {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap, lockRankMheapSpecial},
+	lockRankTrace:           {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap},
+	lockRankTraceStackTab:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankDefer, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR, lockRankExecR, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankNetpollInit, lockRankHchan, lockRankNotifyList, lockRankSudog, lockRankRoot, lockRankItab, lockRankReflectOffs, lockRankUserArenaState, lockRankTraceBuf, lockRankTraceStrings, lockRankFin, lockRankSpanSetSpine, lockRankMspanSpecial, lockRankGcBitsArenas, lockRankProfInsert, lockRankProfBlock, lockRankProfMemActive, lockRankProfMemFuture, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankWbufSpans, lockRankMheap, lockRankTrace},
+	lockRankPanic:           {},
+	lockRankDeadlock:        {lockRankPanic, lockRankDeadlock},
+	lockRankRaceFini:        {lockRankPanic},
+	lockRankAllocmRInternal: {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankAllocmW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankAllocmR},
+	lockRankExecRInternal:   {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankTestR, lockRankExecW, lockRankCpuprof, lockRankPollDesc, lockRankWakeableSleep, lockRankExecR},
+	lockRankTestRInternal:   {lockRankTestR, lockRankTestW},
 }
diff --git a/src/runtime/mklockrank.go b/src/runtime/mklockrank.go
index d9ffcbef8d..c8e34d8f00 100644
--- a/src/runtime/mklockrank.go
+++ b/src/runtime/mklockrank.go
@@ -203,17 +203,19 @@ panic < deadlock;
 # raceFini is only held while exiting.
 panic < raceFini;
 
-# RWMutex
-allocmW,
-  execW,
-  testW
-< rwmutexW;
+# RWMutex internal read lock
 
-rwmutexW,
-  allocmR,
-  execR,
-  testR
-< rwmutexR;
+allocmR,
+  allocmW
+< allocmRInternal;
+
+execR,
+  execW
+< execRInternal;
+
+testR,
+  testW
+< testRInternal;
 `
 
 // cyclicRanks lists lock ranks that allow multiple locks of the same
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index b9715f267e..c487da652e 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -759,8 +759,8 @@ func schedinit() {
 	lockInit(&reflectOffs.lock, lockRankReflectOffs)
 	lockInit(&finlock, lockRankFin)
 	lockInit(&cpuprof.lock, lockRankCpuprof)
-	allocmLock.init(lockRankAllocmR, lockRankAllocmW)
-	execLock.init(lockRankExecR, lockRankExecW)
+	allocmLock.init(lockRankAllocmR, lockRankAllocmRInternal, lockRankAllocmW)
+	execLock.init(lockRankExecR, lockRankExecRInternal, lockRankExecW)
 	traceLockInit()
 	// Enforce that this lock is always a leaf lock.
 	// All of this lock's critical sections should be
diff --git a/src/runtime/rwmutex.go b/src/runtime/rwmutex.go
index 89fe16c10d..34d8f675c1 100644
--- a/src/runtime/rwmutex.go
+++ b/src/runtime/rwmutex.go
@@ -27,7 +27,6 @@ type rwmutex struct {
 	readerWait  atomic.Int32 // number of departing readers
 
 	readRank  lockRank // semantic lock rank for read locking
-	writeRank lockRank // semantic lock rank for write locking
 }
 
 // Lock ranking an rwmutex has two aspects:
@@ -41,21 +40,28 @@ type rwmutex struct {
 // rLock and wLock. These have lock order requirements: wLock must be locked
 // before rLock. This also needs to be represented in the lock rank.
 //
-// Internal ranking is represented by assigning ranks rwmutexR and rwmutexW to
-// rLock and wLock, respectively.
-//
 // Semantic ranking is represented by acquiring readRank during read lock and
 // writeRank during write lock.
 //
-// readRank is always taken before rwmutexR and writeRank is always taken
-// before rwmutexW, so each unique rwmutex must record this order in the lock
-// ranking.
-func (rw *rwmutex) init(readRank, writeRank lockRank) {
+// wLock is held for the duration of a write lock, so it uses writeRank
+// directly, both for semantic and internal ranking. rLock is only held
+// temporarily inside the rlock/lock methods, so it uses readRankInternal to
+// represent internal ranking. Semantic ranking is represented by a separate
+// acquire of readRank for the duration of a read lock.
+//
+// The lock ranking must document this ordering:
+// - readRankInternal is a leaf lock.
+// - readRank is taken before readRankInternal.
+// - writeRank is taken before readRankInternal.
+// - readRank is placed in the lock order wherever a read lock of this rwmutex
+//   belongs.
+// - writeRank is placed in the lock order wherever a write lock of this
+//   rwmutex belongs.
+func (rw *rwmutex) init(readRank, readRankInternal, writeRank lockRank) {
 	rw.readRank = readRank
-	rw.writeRank = writeRank
 
-	lockInit(&rw.rLock, lockRankRwmutexR)
-	lockInit(&rw.wLock, lockRankRwmutexW)
+	lockInit(&rw.rLock, readRankInternal)
+	lockInit(&rw.wLock, writeRank)
 }
 
 const rwmutexMaxReaders = 1 << 30
@@ -117,7 +123,6 @@ func (rw *rwmutex) runlock() {
 // lock locks rw for writing.
 func (rw *rwmutex) lock() {
 	// Resolve competition with other writers and stick to our P.
-	acquireLockRank(rw.writeRank)
 	lock(&rw.wLock)
 	m := getg().m
 	// Announce that there is a pending writer.
@@ -159,5 +164,4 @@ func (rw *rwmutex) unlock() {
 	unlock(&rw.rLock)
 	// Allow other writers to proceed.
 	unlock(&rw.wLock)
-	releaseLockRank(rw.writeRank)
 }