libgo/go/runtime/lockrank.go

   1 // Copyright 2020 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // This file records the static ranks of the locks in the runtime. If a lock
   6 // is not given a rank, then it is assumed to be a leaf lock, which means no other
   7 // lock can be acquired while it is held. Therefore, leaf locks do not need to be
   8 // given an explicit rank. We list all of the architecture-independent leaf locks
   9 // for documentation purposes, but don't list any of the architecture-dependent
  10 // locks (which are all leaf locks). debugLock is ignored for ranking, since it is used
  11 // when printing out lock ranking errors.
  12 //
  13 // lockInit(l *mutex, rank int) is used to set the rank of lock before it is used.
  14 // If there is no clear place to initialize a lock, then the rank of a lock can be
  15 // specified during the lock call itself via lockWithrank(l *mutex, rank int).
  16 //
  17 // Besides the static lock ranking (which is a total ordering of the locks), we
  18 // also represent and enforce the actual partial order among the locks in the
  19 // arcs[] array below. That is, if it is possible that lock B can be acquired when
  20 // lock A is the previous acquired lock that is still held, then there should be
  21 // an entry for A in arcs[B][]. We will currently fail not only if the total order
  22 // (the lock ranking) is violated, but also if there is a missing entry in the
  23 // partial order.
  24
  25 package runtime
  26
  27 type lockRank int
  28
  29 // Constants representing the lock rank of the architecture-independent locks in
  30 // the runtime. Locks with lower rank must be taken before locks with higher
  31 // rank.
  32 const (
  33         lockRankDummy lockRank = iota
  34
  35         // Locks held above sched
  36         lockRankSysmon
  37         lockRankScavenge
  38         lockRankForcegc
  39         lockRankSweepWaiters
  40         lockRankAssistQueue
  41         lockRankCpuprof
  42         lockRankSweep
  43
  44         lockRankPollDesc
  45         lockRankSched
  46         lockRankDeadlock
  47         lockRankAllg
  48         lockRankAllp
  49
  50         lockRankTimers // Multiple timers locked simultaneously in destroy()
  51         lockRankItab
  52         lockRankReflectOffs
  53         lockRankHchan // Multiple hchans acquired in lock order in syncadjustsudogs()
  54         lockRankTraceBuf
  55         lockRankFin
  56         lockRankNotifyList
  57         lockRankTraceStrings
  58         lockRankMspanSpecial
  59         lockRankProf
  60         lockRankGcBitsArenas
  61         lockRankRoot
  62         lockRankTrace
  63         lockRankTraceStackTab
  64         lockRankNetpollInit
  65
  66         lockRankRwmutexW
  67         lockRankRwmutexR
  68
  69         lockRankSpanSetSpine
  70         lockRankGscan
  71         lockRankStackpool
  72         lockRankStackLarge
  73         lockRankDefer
  74         lockRankSudog
  75
  76         // Memory-related non-leaf locks
  77         lockRankWbufSpans
  78         lockRankMheap
  79         lockRankMheapSpecial
  80
  81         // Memory-related leaf locks
  82         lockRankGlobalAlloc
  83         lockRankPageAllocScav
  84
  85         // Other leaf locks
  86         lockRankGFree
  87         // Generally, hchan must be acquired before gscan. But in one specific
  88         // case (in syncadjustsudogs from markroot after the g has been suspended
  89         // by suspendG), we allow gscan to be acquired, and then an hchan lock. To
  90         // allow this case, we get this lockRankHchanLeaf rank in
  91         // syncadjustsudogs(), rather than lockRankHchan. By using this special
  92         // rank, we don't allow any further locks to be acquired other than more
  93         // hchan locks.
  94         lockRankHchanLeaf
  95         lockRankPanic
  96
  97         // Leaf locks with no dependencies, so these constants are not actually used anywhere.
  98         // There are other architecture-dependent leaf locks as well.
  99         lockRankNewmHandoff
 100         lockRankDebugPtrmask
 101         lockRankFaketimeState
 102         lockRankTicks
 103         lockRankRaceFini
 104         lockRankPollCache
 105         lockRankDebug
 106 )
 107
 108 // lockRankLeafRank is the rank of lock that does not have a declared rank, and hence is
 109 // a leaf lock.
 110 const lockRankLeafRank lockRank = 1000
 111
 112 // lockNames gives the names associated with each of the above ranks
 113 var lockNames = []string{
 114         lockRankDummy: "",
 115
 116         lockRankSysmon:       "sysmon",
 117         lockRankScavenge:     "scavenge",
 118         lockRankForcegc:      "forcegc",
 119         lockRankSweepWaiters: "sweepWaiters",
 120         lockRankAssistQueue:  "assistQueue",
 121         lockRankCpuprof:      "cpuprof",
 122         lockRankSweep:        "sweep",
 123
 124         lockRankPollDesc: "pollDesc",
 125         lockRankSched:    "sched",
 126         lockRankDeadlock: "deadlock",
 127         lockRankAllg:     "allg",
 128         lockRankAllp:     "allp",
 129
 130         lockRankTimers:      "timers",
 131         lockRankItab:        "itab",
 132         lockRankReflectOffs: "reflectOffs",
 133
 134         lockRankHchan:         "hchan",
 135         lockRankTraceBuf:      "traceBuf",
 136         lockRankFin:           "fin",
 137         lockRankNotifyList:    "notifyList",
 138         lockRankTraceStrings:  "traceStrings",
 139         lockRankMspanSpecial:  "mspanSpecial",
 140         lockRankProf:          "prof",
 141         lockRankGcBitsArenas:  "gcBitsArenas",
 142         lockRankRoot:          "root",
 143         lockRankTrace:         "trace",
 144         lockRankTraceStackTab: "traceStackTab",
 145         lockRankNetpollInit:   "netpollInit",
 146
 147         lockRankRwmutexW: "rwmutexW",
 148         lockRankRwmutexR: "rwmutexR",
 149
 150         lockRankSpanSetSpine: "spanSetSpine",
 151         lockRankGscan:        "gscan",
 152         lockRankStackpool:    "stackpool",
 153         lockRankStackLarge:   "stackLarge",
 154         lockRankDefer:        "defer",
 155         lockRankSudog:        "sudog",
 156
 157         lockRankWbufSpans:    "wbufSpans",
 158         lockRankMheap:        "mheap",
 159         lockRankMheapSpecial: "mheapSpecial",
 160
 161         lockRankGlobalAlloc:   "globalAlloc.mutex",
 162         lockRankPageAllocScav: "pageAlloc.scav.lock",
 163
 164         lockRankGFree:     "gFree",
 165         lockRankHchanLeaf: "hchanLeaf",
 166         lockRankPanic:     "panic",
 167
 168         lockRankNewmHandoff:   "newmHandoff.lock",
 169         lockRankDebugPtrmask:  "debugPtrmask.lock",
 170         lockRankFaketimeState: "faketimeState.lock",
 171         lockRankTicks:         "ticks.lock",
 172         lockRankRaceFini:      "raceFiniLock",
 173         lockRankPollCache:     "pollCache.lock",
 174         lockRankDebug:         "debugLock",
 175 }
 176
 177 func (rank lockRank) String() string {
 178         if rank == 0 {
 179                 return "UNKNOWN"
 180         }
 181         if rank == lockRankLeafRank {
 182                 return "LEAF"
 183         }
 184         return lockNames[rank]
 185 }
 186
 187 // lockPartialOrder is a partial order among the various lock types, listing the
 188 // immediate ordering that has actually been observed in the runtime. Each entry
 189 // (which corresponds to a particular lock rank) specifies the list of locks
 190 // that can already be held immediately "above" it.
 191 //
 192 // So, for example, the lockRankSched entry shows that all the locks preceding
 193 // it in rank can actually be held. The allp lock shows that only the sysmon or
 194 // sched lock can be held immediately above it when it is acquired.
 195 var lockPartialOrder [][]lockRank = [][]lockRank{
 196         lockRankDummy:         {},
 197         lockRankSysmon:        {},
 198         lockRankScavenge:      {lockRankSysmon},
 199         lockRankForcegc:       {lockRankSysmon},
 200         lockRankSweepWaiters:  {},
 201         lockRankAssistQueue:   {},
 202         lockRankCpuprof:       {},
 203         lockRankSweep:         {},
 204         lockRankPollDesc:      {},
 205         lockRankSched:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc},
 206         lockRankDeadlock:      {lockRankDeadlock},
 207         lockRankAllg:          {lockRankSysmon, lockRankSched},
 208         lockRankAllp:          {lockRankSysmon, lockRankSched},
 209         lockRankTimers:        {lockRankSysmon, lockRankScavenge, lockRankPollDesc, lockRankSched, lockRankAllp, lockRankTimers},
 210         lockRankItab:          {},
 211         lockRankReflectOffs:   {lockRankItab},
 212         lockRankHchan:         {lockRankScavenge, lockRankSweep, lockRankHchan},
 213         lockRankTraceBuf:      {lockRankSysmon, lockRankScavenge},
 214         lockRankFin:           {lockRankSysmon, lockRankScavenge, lockRankSched, lockRankAllg, lockRankTimers, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf},
 215         lockRankNotifyList:    {},
 216         lockRankTraceStrings:  {lockRankTraceBuf},
 217         lockRankMspanSpecial:  {lockRankSysmon, lockRankScavenge, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankItab, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankNotifyList, lockRankTraceStrings},
 218         lockRankProf:          {lockRankSysmon, lockRankScavenge, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankItab, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankNotifyList, lockRankTraceStrings},
 219         lockRankGcBitsArenas:  {lockRankSysmon, lockRankScavenge, lockRankAssistQueue, lockRankCpuprof, lockRankSched, lockRankAllg, lockRankTimers, lockRankItab, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankNotifyList, lockRankTraceStrings},
 220         lockRankRoot:          {},
 221         lockRankTrace:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankAssistQueue, lockRankSweep, lockRankSched, lockRankHchan, lockRankTraceBuf, lockRankTraceStrings, lockRankRoot},
 222         lockRankTraceStackTab: {lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankSched, lockRankAllg, lockRankTimers, lockRankHchan, lockRankTraceBuf, lockRankFin, lockRankNotifyList, lockRankTraceStrings, lockRankRoot, lockRankTrace},
 223         lockRankNetpollInit:   {lockRankTimers},
 224
 225         lockRankRwmutexW: {},
 226         lockRankRwmutexR: {lockRankSysmon, lockRankRwmutexW},
 227
 228         lockRankSpanSetSpine:  {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankItab, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankNotifyList, lockRankTraceStrings},
 229         lockRankGscan:         {lockRankSysmon, lockRankScavenge, lockRankForcegc, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankSched, lockRankTimers, lockRankItab, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankFin, lockRankNotifyList, lockRankTraceStrings, lockRankProf, lockRankGcBitsArenas, lockRankRoot, lockRankTrace, lockRankTraceStackTab, lockRankNetpollInit, lockRankSpanSetSpine},
 230         lockRankStackpool:     {lockRankSysmon, lockRankScavenge, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankSched, lockRankTimers, lockRankItab, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankFin, lockRankNotifyList, lockRankTraceStrings, lockRankProf, lockRankGcBitsArenas, lockRankRoot, lockRankTrace, lockRankTraceStackTab, lockRankNetpollInit, lockRankRwmutexR, lockRankSpanSetSpine, lockRankGscan},
 231         lockRankStackLarge:    {lockRankSysmon, lockRankAssistQueue, lockRankSched, lockRankItab, lockRankHchan, lockRankProf, lockRankGcBitsArenas, lockRankRoot, lockRankSpanSetSpine, lockRankGscan},
 232         lockRankDefer:         {},
 233         lockRankSudog:         {lockRankHchan, lockRankNotifyList},
 234         lockRankWbufSpans:     {lockRankSysmon, lockRankScavenge, lockRankSweepWaiters, lockRankAssistQueue, lockRankSweep, lockRankPollDesc, lockRankSched, lockRankAllg, lockRankTimers, lockRankItab, lockRankReflectOffs, lockRankHchan, lockRankFin, lockRankNotifyList, lockRankTraceStrings, lockRankMspanSpecial, lockRankProf, lockRankRoot, lockRankGscan, lockRankDefer, lockRankSudog},
 235         lockRankMheap:         {lockRankSysmon, lockRankScavenge, lockRankSweepWaiters, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankItab, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankFin, lockRankNotifyList, lockRankTraceStrings, lockRankMspanSpecial, lockRankProf, lockRankGcBitsArenas, lockRankRoot, lockRankSpanSetSpine, lockRankGscan, lockRankStackpool, lockRankStackLarge, lockRankDefer, lockRankSudog, lockRankWbufSpans},
 236         lockRankMheapSpecial:  {lockRankSysmon, lockRankScavenge, lockRankAssistQueue, lockRankCpuprof, lockRankSweep, lockRankPollDesc, lockRankSched, lockRankAllg, lockRankAllp, lockRankTimers, lockRankItab, lockRankReflectOffs, lockRankHchan, lockRankTraceBuf, lockRankNotifyList, lockRankTraceStrings},
 237         lockRankGlobalAlloc:   {lockRankProf, lockRankSpanSetSpine, lockRankMheap, lockRankMheapSpecial},
 238         lockRankPageAllocScav: {lockRankMheap},
 239
 240         lockRankGFree:     {lockRankSched},
 241         lockRankHchanLeaf: {lockRankGscan, lockRankHchanLeaf},
 242         lockRankPanic:     {lockRankDeadlock}, // plus any other lock held on throw.
 243
 244         lockRankNewmHandoff:   {},
 245         lockRankDebugPtrmask:  {},
 246         lockRankFaketimeState: {},
 247         lockRankTicks:         {},
 248         lockRankRaceFini:      {},
 249         lockRankPollCache:     {},
 250         lockRankDebug:         {},
 251 }