github.com/AESNooper/go/src@v0.0.0-20220218095104-b56a4ab1bbbb/runtime/runtime2.go (about) 1 // Copyright 2009 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 package runtime 6 7 import ( 8 "internal/goarch" 9 "runtime/internal/atomic" 10 "unsafe" 11 ) 12 13 // defined constants 14 const ( 15 // G status 16 // 17 // Beyond indicating the general state of a G, the G status 18 // acts like a lock on the goroutine's stack (and hence its 19 // ability to execute user code). 20 // 21 // If you add to this list, add to the list 22 // of "okay during garbage collection" status 23 // in mgcmark.go too. 24 // 25 // TODO(austin): The _Gscan bit could be much lighter-weight. 26 // For example, we could choose not to run _Gscanrunnable 27 // goroutines found in the run queue, rather than CAS-looping 28 // until they become _Grunnable. And transitions like 29 // _Gscanwaiting -> _Gscanrunnable are actually okay because 30 // they don't affect stack ownership. 31 32 // _Gidle means this goroutine was just allocated and has not 33 // yet been initialized. 34 _Gidle = iota // 0 35 36 // _Grunnable means this goroutine is on a run queue. It is 37 // not currently executing user code. The stack is not owned. 38 _Grunnable // 1 39 40 // _Grunning means this goroutine may execute user code. The 41 // stack is owned by this goroutine. It is not on a run queue. 42 // It is assigned an M and a P (g.m and g.m.p are valid). 43 _Grunning // 2 44 45 // _Gsyscall means this goroutine is executing a system call. 46 // It is not executing user code. The stack is owned by this 47 // goroutine. It is not on a run queue. It is assigned an M. 48 _Gsyscall // 3 49 50 // _Gwaiting means this goroutine is blocked in the runtime. 51 // It is not executing user code. It is not on a run queue, 52 // but should be recorded somewhere (e.g., a channel wait 53 // queue) so it can be ready()d when necessary. The stack is 54 // not owned *except* that a channel operation may read or 55 // write parts of the stack under the appropriate channel 56 // lock. Otherwise, it is not safe to access the stack after a 57 // goroutine enters _Gwaiting (e.g., it may get moved). 58 _Gwaiting // 4 59 60 // _Gmoribund_unused is currently unused, but hardcoded in gdb 61 // scripts. 62 _Gmoribund_unused // 5 63 64 // _Gdead means this goroutine is currently unused. It may be 65 // just exited, on a free list, or just being initialized. It 66 // is not executing user code. It may or may not have a stack 67 // allocated. The G and its stack (if any) are owned by the M 68 // that is exiting the G or that obtained the G from the free 69 // list. 70 _Gdead // 6 71 72 // _Genqueue_unused is currently unused. 73 _Genqueue_unused // 7 74 75 // _Gcopystack means this goroutine's stack is being moved. It 76 // is not executing user code and is not on a run queue. The 77 // stack is owned by the goroutine that put it in _Gcopystack. 78 _Gcopystack // 8 79 80 // _Gpreempted means this goroutine stopped itself for a 81 // suspendG preemption. It is like _Gwaiting, but nothing is 82 // yet responsible for ready()ing it. Some suspendG must CAS 83 // the status to _Gwaiting to take responsibility for 84 // ready()ing this G. 85 _Gpreempted // 9 86 87 // _Gscan combined with one of the above states other than 88 // _Grunning indicates that GC is scanning the stack. The 89 // goroutine is not executing user code and the stack is owned 90 // by the goroutine that set the _Gscan bit. 91 // 92 // _Gscanrunning is different: it is used to briefly block 93 // state transitions while GC signals the G to scan its own 94 // stack. This is otherwise like _Grunning. 95 // 96 // atomicstatus&~Gscan gives the state the goroutine will 97 // return to when the scan completes. 98 _Gscan = 0x1000 99 _Gscanrunnable = _Gscan + _Grunnable // 0x1001 100 _Gscanrunning = _Gscan + _Grunning // 0x1002 101 _Gscansyscall = _Gscan + _Gsyscall // 0x1003 102 _Gscanwaiting = _Gscan + _Gwaiting // 0x1004 103 _Gscanpreempted = _Gscan + _Gpreempted // 0x1009 104 ) 105 106 const ( 107 // P status 108 109 // _Pidle means a P is not being used to run user code or the 110 // scheduler. Typically, it's on the idle P list and available 111 // to the scheduler, but it may just be transitioning between 112 // other states. 113 // 114 // The P is owned by the idle list or by whatever is 115 // transitioning its state. Its run queue is empty. 116 _Pidle = iota 117 118 // _Prunning means a P is owned by an M and is being used to 119 // run user code or the scheduler. Only the M that owns this P 120 // is allowed to change the P's status from _Prunning. The M 121 // may transition the P to _Pidle (if it has no more work to 122 // do), _Psyscall (when entering a syscall), or _Pgcstop (to 123 // halt for the GC). The M may also hand ownership of the P 124 // off directly to another M (e.g., to schedule a locked G). 125 _Prunning 126 127 // _Psyscall means a P is not running user code. It has 128 // affinity to an M in a syscall but is not owned by it and 129 // may be stolen by another M. This is similar to _Pidle but 130 // uses lightweight transitions and maintains M affinity. 131 // 132 // Leaving _Psyscall must be done with a CAS, either to steal 133 // or retake the P. Note that there's an ABA hazard: even if 134 // an M successfully CASes its original P back to _Prunning 135 // after a syscall, it must understand the P may have been 136 // used by another M in the interim. 137 _Psyscall 138 139 // _Pgcstop means a P is halted for STW and owned by the M 140 // that stopped the world. The M that stopped the world 141 // continues to use its P, even in _Pgcstop. Transitioning 142 // from _Prunning to _Pgcstop causes an M to release its P and 143 // park. 144 // 145 // The P retains its run queue and startTheWorld will restart 146 // the scheduler on Ps with non-empty run queues. 147 _Pgcstop 148 149 // _Pdead means a P is no longer used (GOMAXPROCS shrank). We 150 // reuse Ps if GOMAXPROCS increases. A dead P is mostly 151 // stripped of its resources, though a few things remain 152 // (e.g., trace buffers). 153 _Pdead 154 ) 155 156 // Mutual exclusion locks. In the uncontended case, 157 // as fast as spin locks (just a few user-level instructions), 158 // but on the contention path they sleep in the kernel. 159 // A zeroed Mutex is unlocked (no need to initialize each lock). 160 // Initialization is helpful for static lock ranking, but not required. 161 type mutex struct { 162 // Empty struct if lock ranking is disabled, otherwise includes the lock rank 163 lockRankStruct 164 // Futex-based impl treats it as uint32 key, 165 // while sema-based impl as M* waitm. 166 // Used to be a union, but unions break precise GC. 167 key uintptr 168 } 169 170 // sleep and wakeup on one-time events. 171 // before any calls to notesleep or notewakeup, 172 // must call noteclear to initialize the Note. 173 // then, exactly one thread can call notesleep 174 // and exactly one thread can call notewakeup (once). 175 // once notewakeup has been called, the notesleep 176 // will return. future notesleep will return immediately. 177 // subsequent noteclear must be called only after 178 // previous notesleep has returned, e.g. it's disallowed 179 // to call noteclear straight after notewakeup. 180 // 181 // notetsleep is like notesleep but wakes up after 182 // a given number of nanoseconds even if the event 183 // has not yet happened. if a goroutine uses notetsleep to 184 // wake up early, it must wait to call noteclear until it 185 // can be sure that no other goroutine is calling 186 // notewakeup. 187 // 188 // notesleep/notetsleep are generally called on g0, 189 // notetsleepg is similar to notetsleep but is called on user g. 190 type note struct { 191 // Futex-based impl treats it as uint32 key, 192 // while sema-based impl as M* waitm. 193 // Used to be a union, but unions break precise GC. 194 key uintptr 195 } 196 197 type funcval struct { 198 fn uintptr 199 // variable-size, fn-specific data here 200 } 201 202 type iface struct { 203 tab *itab 204 data unsafe.Pointer 205 } 206 207 type eface struct { 208 _type *_type 209 data unsafe.Pointer 210 } 211 212 func efaceOf(ep *interface{}) *eface { 213 return (*eface)(unsafe.Pointer(ep)) 214 } 215 216 // The guintptr, muintptr, and puintptr are all used to bypass write barriers. 217 // It is particularly important to avoid write barriers when the current P has 218 // been released, because the GC thinks the world is stopped, and an 219 // unexpected write barrier would not be synchronized with the GC, 220 // which can lead to a half-executed write barrier that has marked the object 221 // but not queued it. If the GC skips the object and completes before the 222 // queuing can occur, it will incorrectly free the object. 223 // 224 // We tried using special assignment functions invoked only when not 225 // holding a running P, but then some updates to a particular memory 226 // word went through write barriers and some did not. This breaks the 227 // write barrier shadow checking mode, and it is also scary: better to have 228 // a word that is completely ignored by the GC than to have one for which 229 // only a few updates are ignored. 230 // 231 // Gs and Ps are always reachable via true pointers in the 232 // allgs and allp lists or (during allocation before they reach those lists) 233 // from stack variables. 234 // 235 // Ms are always reachable via true pointers either from allm or 236 // freem. Unlike Gs and Ps we do free Ms, so it's important that 237 // nothing ever hold an muintptr across a safe point. 238 239 // A guintptr holds a goroutine pointer, but typed as a uintptr 240 // to bypass write barriers. It is used in the Gobuf goroutine state 241 // and in scheduling lists that are manipulated without a P. 242 // 243 // The Gobuf.g goroutine pointer is almost always updated by assembly code. 244 // In one of the few places it is updated by Go code - func save - it must be 245 // treated as a uintptr to avoid a write barrier being emitted at a bad time. 246 // Instead of figuring out how to emit the write barriers missing in the 247 // assembly manipulation, we change the type of the field to uintptr, 248 // so that it does not require write barriers at all. 249 // 250 // Goroutine structs are published in the allg list and never freed. 251 // That will keep the goroutine structs from being collected. 252 // There is never a time that Gobuf.g's contain the only references 253 // to a goroutine: the publishing of the goroutine in allg comes first. 254 // Goroutine pointers are also kept in non-GC-visible places like TLS, 255 // so I can't see them ever moving. If we did want to start moving data 256 // in the GC, we'd need to allocate the goroutine structs from an 257 // alternate arena. Using guintptr doesn't make that problem any worse. 258 type guintptr uintptr 259 260 //go:nosplit 261 func (gp guintptr) ptr() *g { return (*g)(unsafe.Pointer(gp)) } 262 263 //go:nosplit 264 func (gp *guintptr) set(g *g) { *gp = guintptr(unsafe.Pointer(g)) } 265 266 //go:nosplit 267 func (gp *guintptr) cas(old, new guintptr) bool { 268 return atomic.Casuintptr((*uintptr)(unsafe.Pointer(gp)), uintptr(old), uintptr(new)) 269 } 270 271 // setGNoWB performs *gp = new without a write barrier. 272 // For times when it's impractical to use a guintptr. 273 //go:nosplit 274 //go:nowritebarrier 275 func setGNoWB(gp **g, new *g) { 276 (*guintptr)(unsafe.Pointer(gp)).set(new) 277 } 278 279 type puintptr uintptr 280 281 //go:nosplit 282 func (pp puintptr) ptr() *p { return (*p)(unsafe.Pointer(pp)) } 283 284 //go:nosplit 285 func (pp *puintptr) set(p *p) { *pp = puintptr(unsafe.Pointer(p)) } 286 287 // muintptr is a *m that is not tracked by the garbage collector. 288 // 289 // Because we do free Ms, there are some additional constrains on 290 // muintptrs: 291 // 292 // 1. Never hold an muintptr locally across a safe point. 293 // 294 // 2. Any muintptr in the heap must be owned by the M itself so it can 295 // ensure it is not in use when the last true *m is released. 296 type muintptr uintptr 297 298 //go:nosplit 299 func (mp muintptr) ptr() *m { return (*m)(unsafe.Pointer(mp)) } 300 301 //go:nosplit 302 func (mp *muintptr) set(m *m) { *mp = muintptr(unsafe.Pointer(m)) } 303 304 // setMNoWB performs *mp = new without a write barrier. 305 // For times when it's impractical to use an muintptr. 306 //go:nosplit 307 //go:nowritebarrier 308 func setMNoWB(mp **m, new *m) { 309 (*muintptr)(unsafe.Pointer(mp)).set(new) 310 } 311 312 type gobuf struct { 313 // The offsets of sp, pc, and g are known to (hard-coded in) libmach. 314 // 315 // ctxt is unusual with respect to GC: it may be a 316 // heap-allocated funcval, so GC needs to track it, but it 317 // needs to be set and cleared from assembly, where it's 318 // difficult to have write barriers. However, ctxt is really a 319 // saved, live register, and we only ever exchange it between 320 // the real register and the gobuf. Hence, we treat it as a 321 // root during stack scanning, which means assembly that saves 322 // and restores it doesn't need write barriers. It's still 323 // typed as a pointer so that any other writes from Go get 324 // write barriers. 325 sp uintptr 326 pc uintptr 327 g guintptr 328 ctxt unsafe.Pointer 329 ret uintptr 330 lr uintptr 331 bp uintptr // for framepointer-enabled architectures 332 } 333 334 // sudog represents a g in a wait list, such as for sending/receiving 335 // on a channel. 336 // 337 // sudog is necessary because the g ↔ synchronization object relation 338 // is many-to-many. A g can be on many wait lists, so there may be 339 // many sudogs for one g; and many gs may be waiting on the same 340 // synchronization object, so there may be many sudogs for one object. 341 // 342 // sudogs are allocated from a special pool. Use acquireSudog and 343 // releaseSudog to allocate and free them. 344 type sudog struct { 345 // The following fields are protected by the hchan.lock of the 346 // channel this sudog is blocking on. shrinkstack depends on 347 // this for sudogs involved in channel ops. 348 349 g *g 350 351 next *sudog 352 prev *sudog 353 elem unsafe.Pointer // data element (may point to stack) 354 355 // The following fields are never accessed concurrently. 356 // For channels, waitlink is only accessed by g. 357 // For semaphores, all fields (including the ones above) 358 // are only accessed when holding a semaRoot lock. 359 360 acquiretime int64 361 releasetime int64 362 ticket uint32 363 364 // isSelect indicates g is participating in a select, so 365 // g.selectDone must be CAS'd to win the wake-up race. 366 isSelect bool 367 368 // success indicates whether communication over channel c 369 // succeeded. It is true if the goroutine was awoken because a 370 // value was delivered over channel c, and false if awoken 371 // because c was closed. 372 success bool 373 374 parent *sudog // semaRoot binary tree 375 waitlink *sudog // g.waiting list or semaRoot 376 waittail *sudog // semaRoot 377 c *hchan // channel 378 } 379 380 type libcall struct { 381 fn uintptr 382 n uintptr // number of parameters 383 args uintptr // parameters 384 r1 uintptr // return values 385 r2 uintptr 386 err uintptr // error number 387 } 388 389 // Stack describes a Go execution stack. 390 // The bounds of the stack are exactly [lo, hi), 391 // with no implicit data structures on either side. 392 type stack struct { 393 lo uintptr 394 hi uintptr 395 } 396 397 // heldLockInfo gives info on a held lock and the rank of that lock 398 type heldLockInfo struct { 399 lockAddr uintptr 400 rank lockRank 401 } 402 403 type g struct { 404 // Stack parameters. 405 // stack describes the actual stack memory: [stack.lo, stack.hi). 406 // stackguard0 is the stack pointer compared in the Go stack growth prologue. 407 // It is stack.lo+StackGuard normally, but can be StackPreempt to trigger a preemption. 408 // stackguard1 is the stack pointer compared in the C stack growth prologue. 409 // It is stack.lo+StackGuard on g0 and gsignal stacks. 410 // It is ~0 on other goroutine stacks, to trigger a call to morestackc (and crash). 411 stack stack // offset known to runtime/cgo 412 stackguard0 uintptr // offset known to liblink 413 stackguard1 uintptr // offset known to liblink 414 415 _panic *_panic // innermost panic - offset known to liblink 416 _defer *_defer // innermost defer 417 m *m // current m; offset known to arm liblink 418 sched gobuf 419 syscallsp uintptr // if status==Gsyscall, syscallsp = sched.sp to use during gc 420 syscallpc uintptr // if status==Gsyscall, syscallpc = sched.pc to use during gc 421 stktopsp uintptr // expected sp at top of stack, to check in traceback 422 // param is a generic pointer parameter field used to pass 423 // values in particular contexts where other storage for the 424 // parameter would be difficult to find. It is currently used 425 // in three ways: 426 // 1. When a channel operation wakes up a blocked goroutine, it sets param to 427 // point to the sudog of the completed blocking operation. 428 // 2. By gcAssistAlloc1 to signal back to its caller that the goroutine completed 429 // the GC cycle. It is unsafe to do so in any other way, because the goroutine's 430 // stack may have moved in the meantime. 431 // 3. By debugCallWrap to pass parameters to a new goroutine because allocating a 432 // closure in the runtime is forbidden. 433 param unsafe.Pointer 434 atomicstatus uint32 435 stackLock uint32 // sigprof/scang lock; TODO: fold in to atomicstatus 436 goid int64 437 schedlink guintptr 438 waitsince int64 // approx time when the g become blocked 439 waitreason waitReason // if status==Gwaiting 440 441 preempt bool // preemption signal, duplicates stackguard0 = stackpreempt 442 preemptStop bool // transition to _Gpreempted on preemption; otherwise, just deschedule 443 preemptShrink bool // shrink stack at synchronous safe point 444 445 // asyncSafePoint is set if g is stopped at an asynchronous 446 // safe point. This means there are frames on the stack 447 // without precise pointer information. 448 asyncSafePoint bool 449 450 paniconfault bool // panic (instead of crash) on unexpected fault address 451 gcscandone bool // g has scanned stack; protected by _Gscan bit in status 452 throwsplit bool // must not split stack 453 // activeStackChans indicates that there are unlocked channels 454 // pointing into this goroutine's stack. If true, stack 455 // copying needs to acquire channel locks to protect these 456 // areas of the stack. 457 activeStackChans bool 458 // parkingOnChan indicates that the goroutine is about to 459 // park on a chansend or chanrecv. Used to signal an unsafe point 460 // for stack shrinking. It's a boolean value, but is updated atomically. 461 parkingOnChan uint8 462 463 raceignore int8 // ignore race detection events 464 sysblocktraced bool // StartTrace has emitted EvGoInSyscall about this goroutine 465 tracking bool // whether we're tracking this G for sched latency statistics 466 trackingSeq uint8 // used to decide whether to track this G 467 runnableStamp int64 // timestamp of when the G last became runnable, only used when tracking 468 runnableTime int64 // the amount of time spent runnable, cleared when running, only used when tracking 469 sysexitticks int64 // cputicks when syscall has returned (for tracing) 470 traceseq uint64 // trace event sequencer 471 tracelastp puintptr // last P emitted an event for this goroutine 472 lockedm muintptr 473 sig uint32 474 writebuf []byte 475 sigcode0 uintptr 476 sigcode1 uintptr 477 sigpc uintptr 478 gopc uintptr // pc of go statement that created this goroutine 479 ancestors *[]ancestorInfo // ancestor information goroutine(s) that created this goroutine (only used if debug.tracebackancestors) 480 startpc uintptr // pc of goroutine function 481 racectx uintptr 482 waiting *sudog // sudog structures this g is waiting on (that have a valid elem ptr); in lock order 483 cgoCtxt []uintptr // cgo traceback context 484 labels unsafe.Pointer // profiler labels 485 timer *timer // cached timer for time.Sleep 486 selectDone uint32 // are we participating in a select and did someone win the race? 487 488 // Per-G GC state 489 490 // gcAssistBytes is this G's GC assist credit in terms of 491 // bytes allocated. If this is positive, then the G has credit 492 // to allocate gcAssistBytes bytes without assisting. If this 493 // is negative, then the G must correct this by performing 494 // scan work. We track this in bytes to make it fast to update 495 // and check for debt in the malloc hot path. The assist ratio 496 // determines how this corresponds to scan work debt. 497 gcAssistBytes int64 498 } 499 500 // gTrackingPeriod is the number of transitions out of _Grunning between 501 // latency tracking runs. 502 const gTrackingPeriod = 8 503 504 const ( 505 // tlsSlots is the number of pointer-sized slots reserved for TLS on some platforms, 506 // like Windows. 507 tlsSlots = 6 508 tlsSize = tlsSlots * goarch.PtrSize 509 ) 510 511 type m struct { 512 g0 *g // goroutine with scheduling stack 513 morebuf gobuf // gobuf arg to morestack 514 divmod uint32 // div/mod denominator for arm - known to liblink 515 516 // Fields not known to debuggers. 517 procid uint64 // for debuggers, but offset not hard-coded 518 gsignal *g // signal-handling g 519 goSigStack gsignalStack // Go-allocated signal handling stack 520 sigmask sigset // storage for saved signal mask 521 tls [tlsSlots]uintptr // thread-local storage (for x86 extern register) 522 mstartfn func() 523 curg *g // current running goroutine 524 caughtsig guintptr // goroutine running during fatal signal 525 p puintptr // attached p for executing go code (nil if not executing go code) 526 nextp puintptr 527 oldp puintptr // the p that was attached before executing a syscall 528 id int64 529 mallocing int32 530 throwing int32 531 preemptoff string // if != "", keep curg running on this m 532 locks int32 533 dying int32 534 profilehz int32 535 spinning bool // m is out of work and is actively looking for work 536 blocked bool // m is blocked on a note 537 newSigstack bool // minit on C thread called sigaltstack 538 printlock int8 539 incgo bool // m is executing a cgo call 540 freeWait uint32 // if == 0, safe to free g0 and delete m (atomic) 541 fastrand uint64 542 needextram bool 543 traceback uint8 544 ncgocall uint64 // number of cgo calls in total 545 ncgo int32 // number of cgo calls currently in progress 546 cgoCallersUse uint32 // if non-zero, cgoCallers in use temporarily 547 cgoCallers *cgoCallers // cgo traceback if crashing in cgo call 548 doesPark bool // non-P running threads: sysmon and newmHandoff never use .park 549 park note 550 alllink *m // on allm 551 schedlink muintptr 552 lockedg guintptr 553 createstack [32]uintptr // stack that created this thread. 554 lockedExt uint32 // tracking for external LockOSThread 555 lockedInt uint32 // tracking for internal lockOSThread 556 nextwaitm muintptr // next m waiting for lock 557 waitunlockf func(*g, unsafe.Pointer) bool 558 waitlock unsafe.Pointer 559 waittraceev byte 560 waittraceskip int 561 startingtrace bool 562 syscalltick uint32 563 freelink *m // on sched.freem 564 565 // mFixup is used to synchronize OS related m state 566 // (credentials etc) use mutex to access. To avoid deadlocks 567 // an atomic.Load() of used being zero in mDoFixupFn() 568 // guarantees fn is nil. 569 mFixup struct { 570 lock mutex 571 used uint32 572 fn func(bool) bool 573 } 574 575 // these are here because they are too large to be on the stack 576 // of low-level NOSPLIT functions. 577 libcall libcall 578 libcallpc uintptr // for cpu profiler 579 libcallsp uintptr 580 libcallg guintptr 581 syscall libcall // stores syscall parameters on windows 582 583 vdsoSP uintptr // SP for traceback while in VDSO call (0 if not in call) 584 vdsoPC uintptr // PC for traceback while in VDSO call 585 586 // preemptGen counts the number of completed preemption 587 // signals. This is used to detect when a preemption is 588 // requested, but fails. Accessed atomically. 589 preemptGen uint32 590 591 // Whether this is a pending preemption signal on this M. 592 // Accessed atomically. 593 signalPending uint32 594 595 dlogPerM 596 597 mOS 598 599 // Up to 10 locks held by this m, maintained by the lock ranking code. 600 locksHeldLen int 601 locksHeld [10]heldLockInfo 602 } 603 604 type p struct { 605 id int32 606 status uint32 // one of pidle/prunning/... 607 link puintptr 608 schedtick uint32 // incremented on every scheduler call 609 syscalltick uint32 // incremented on every system call 610 sysmontick sysmontick // last tick observed by sysmon 611 m muintptr // back-link to associated m (nil if idle) 612 mcache *mcache 613 pcache pageCache 614 raceprocctx uintptr 615 616 deferpool []*_defer // pool of available defer structs (see panic.go) 617 deferpoolbuf [32]*_defer 618 619 // Cache of goroutine ids, amortizes accesses to runtime·sched.goidgen. 620 goidcache uint64 621 goidcacheend uint64 622 623 // Queue of runnable goroutines. Accessed without lock. 624 runqhead uint32 625 runqtail uint32 626 runq [256]guintptr 627 // runnext, if non-nil, is a runnable G that was ready'd by 628 // the current G and should be run next instead of what's in 629 // runq if there's time remaining in the running G's time 630 // slice. It will inherit the time left in the current time 631 // slice. If a set of goroutines is locked in a 632 // communicate-and-wait pattern, this schedules that set as a 633 // unit and eliminates the (potentially large) scheduling 634 // latency that otherwise arises from adding the ready'd 635 // goroutines to the end of the run queue. 636 // 637 // Note that while other P's may atomically CAS this to zero, 638 // only the owner P can CAS it to a valid G. 639 runnext guintptr 640 641 // Available G's (status == Gdead) 642 gFree struct { 643 gList 644 n int32 645 } 646 647 sudogcache []*sudog 648 sudogbuf [128]*sudog 649 650 // Cache of mspan objects from the heap. 651 mspancache struct { 652 // We need an explicit length here because this field is used 653 // in allocation codepaths where write barriers are not allowed, 654 // and eliminating the write barrier/keeping it eliminated from 655 // slice updates is tricky, moreso than just managing the length 656 // ourselves. 657 len int 658 buf [128]*mspan 659 } 660 661 tracebuf traceBufPtr 662 663 // traceSweep indicates the sweep events should be traced. 664 // This is used to defer the sweep start event until a span 665 // has actually been swept. 666 traceSweep bool 667 // traceSwept and traceReclaimed track the number of bytes 668 // swept and reclaimed by sweeping in the current sweep loop. 669 traceSwept, traceReclaimed uintptr 670 671 palloc persistentAlloc // per-P to avoid mutex 672 673 _ uint32 // Alignment for atomic fields below 674 675 // The when field of the first entry on the timer heap. 676 // This is updated using atomic functions. 677 // This is 0 if the timer heap is empty. 678 timer0When uint64 679 680 // The earliest known nextwhen field of a timer with 681 // timerModifiedEarlier status. Because the timer may have been 682 // modified again, there need not be any timer with this value. 683 // This is updated using atomic functions. 684 // This is 0 if there are no timerModifiedEarlier timers. 685 timerModifiedEarliest uint64 686 687 // Per-P GC state 688 gcAssistTime int64 // Nanoseconds in assistAlloc 689 gcFractionalMarkTime int64 // Nanoseconds in fractional mark worker (atomic) 690 691 // gcMarkWorkerMode is the mode for the next mark worker to run in. 692 // That is, this is used to communicate with the worker goroutine 693 // selected for immediate execution by 694 // gcController.findRunnableGCWorker. When scheduling other goroutines, 695 // this field must be set to gcMarkWorkerNotWorker. 696 gcMarkWorkerMode gcMarkWorkerMode 697 // gcMarkWorkerStartTime is the nanotime() at which the most recent 698 // mark worker started. 699 gcMarkWorkerStartTime int64 700 701 // gcw is this P's GC work buffer cache. The work buffer is 702 // filled by write barriers, drained by mutator assists, and 703 // disposed on certain GC state transitions. 704 gcw gcWork 705 706 // wbBuf is this P's GC write barrier buffer. 707 // 708 // TODO: Consider caching this in the running G. 709 wbBuf wbBuf 710 711 runSafePointFn uint32 // if 1, run sched.safePointFn at next safe point 712 713 // statsSeq is a counter indicating whether this P is currently 714 // writing any stats. Its value is even when not, odd when it is. 715 statsSeq uint32 716 717 // Lock for timers. We normally access the timers while running 718 // on this P, but the scheduler can also do it from a different P. 719 timersLock mutex 720 721 // Actions to take at some time. This is used to implement the 722 // standard library's time package. 723 // Must hold timersLock to access. 724 timers []*timer 725 726 // Number of timers in P's heap. 727 // Modified using atomic instructions. 728 numTimers uint32 729 730 // Number of timerDeleted timers in P's heap. 731 // Modified using atomic instructions. 732 deletedTimers uint32 733 734 // Race context used while executing timer functions. 735 timerRaceCtx uintptr 736 737 // scannableStackSizeDelta accumulates the amount of stack space held by 738 // live goroutines (i.e. those eligible for stack scanning). 739 // Flushed to gcController.scannableStackSize once scannableStackSizeSlack 740 // or -scannableStackSizeSlack is reached. 741 scannableStackSizeDelta int64 742 743 // preempt is set to indicate that this P should be enter the 744 // scheduler ASAP (regardless of what G is running on it). 745 preempt bool 746 747 // Padding is no longer needed. False sharing is now not a worry because p is large enough 748 // that its size class is an integer multiple of the cache line size (for any of our architectures). 749 } 750 751 type schedt struct { 752 // accessed atomically. keep at top to ensure alignment on 32-bit systems. 753 goidgen uint64 754 lastpoll uint64 // time of last network poll, 0 if currently polling 755 pollUntil uint64 // time to which current poll is sleeping 756 757 lock mutex 758 759 // When increasing nmidle, nmidlelocked, nmsys, or nmfreed, be 760 // sure to call checkdead(). 761 762 midle muintptr // idle m's waiting for work 763 nmidle int32 // number of idle m's waiting for work 764 nmidlelocked int32 // number of locked m's waiting for work 765 mnext int64 // number of m's that have been created and next M ID 766 maxmcount int32 // maximum number of m's allowed (or die) 767 nmsys int32 // number of system m's not counted for deadlock 768 nmfreed int64 // cumulative number of freed m's 769 770 ngsys uint32 // number of system goroutines; updated atomically 771 772 pidle puintptr // idle p's 773 npidle uint32 774 nmspinning uint32 // See "Worker thread parking/unparking" comment in proc.go. 775 776 // Global runnable queue. 777 runq gQueue 778 runqsize int32 779 780 // disable controls selective disabling of the scheduler. 781 // 782 // Use schedEnableUser to control this. 783 // 784 // disable is protected by sched.lock. 785 disable struct { 786 // user disables scheduling of user goroutines. 787 user bool 788 runnable gQueue // pending runnable Gs 789 n int32 // length of runnable 790 } 791 792 // Global cache of dead G's. 793 gFree struct { 794 lock mutex 795 stack gList // Gs with stacks 796 noStack gList // Gs without stacks 797 n int32 798 } 799 800 // Central cache of sudog structs. 801 sudoglock mutex 802 sudogcache *sudog 803 804 // Central pool of available defer structs. 805 deferlock mutex 806 deferpool *_defer 807 808 // freem is the list of m's waiting to be freed when their 809 // m.exited is set. Linked through m.freelink. 810 freem *m 811 812 gcwaiting uint32 // gc is waiting to run 813 stopwait int32 814 stopnote note 815 sysmonwait uint32 816 sysmonnote note 817 818 // While true, sysmon not ready for mFixup calls. 819 // Accessed atomically. 820 sysmonStarting uint32 821 822 // safepointFn should be called on each P at the next GC 823 // safepoint if p.runSafePointFn is set. 824 safePointFn func(*p) 825 safePointWait int32 826 safePointNote note 827 828 profilehz int32 // cpu profiling rate 829 830 procresizetime int64 // nanotime() of last change to gomaxprocs 831 totaltime int64 // ∫gomaxprocs dt up to procresizetime 832 833 // sysmonlock protects sysmon's actions on the runtime. 834 // 835 // Acquire and hold this mutex to block sysmon from interacting 836 // with the rest of the runtime. 837 sysmonlock mutex 838 839 _ uint32 // ensure timeToRun has 8-byte alignment 840 841 // timeToRun is a distribution of scheduling latencies, defined 842 // as the sum of time a G spends in the _Grunnable state before 843 // it transitions to _Grunning. 844 // 845 // timeToRun is protected by sched.lock. 846 timeToRun timeHistogram 847 } 848 849 // Values for the flags field of a sigTabT. 850 const ( 851 _SigNotify = 1 << iota // let signal.Notify have signal, even if from kernel 852 _SigKill // if signal.Notify doesn't take it, exit quietly 853 _SigThrow // if signal.Notify doesn't take it, exit loudly 854 _SigPanic // if the signal is from the kernel, panic 855 _SigDefault // if the signal isn't explicitly requested, don't monitor it 856 _SigGoExit // cause all runtime procs to exit (only used on Plan 9). 857 _SigSetStack // add SA_ONSTACK to libc handler 858 _SigUnblock // always unblock; see blockableSig 859 _SigIgn // _SIG_DFL action is to ignore the signal 860 ) 861 862 // Layout of in-memory per-function information prepared by linker 863 // See https://golang.org/s/go12symtab. 864 // Keep in sync with linker (../cmd/link/internal/ld/pcln.go:/pclntab) 865 // and with package debug/gosym and with symtab.go in package runtime. 866 type _func struct { 867 entryoff uint32 // start pc, as offset from moduledata.text/pcHeader.textStart 868 nameoff int32 // function name 869 870 args int32 // in/out args size 871 deferreturn uint32 // offset of start of a deferreturn call instruction from entry, if any. 872 873 pcsp uint32 874 pcfile uint32 875 pcln uint32 876 npcdata uint32 877 cuOffset uint32 // runtime.cutab offset of this function's CU 878 funcID funcID // set for certain special runtime functions 879 flag funcFlag 880 _ [1]byte // pad 881 nfuncdata uint8 // must be last, must end on a uint32-aligned boundary 882 } 883 884 // Pseudo-Func that is returned for PCs that occur in inlined code. 885 // A *Func can be either a *_func or a *funcinl, and they are distinguished 886 // by the first uintptr. 887 type funcinl struct { 888 ones uint32 // set to ^0 to distinguish from _func 889 entry uintptr // entry of the real (the "outermost") frame 890 name string 891 file string 892 line int 893 } 894 895 // layout of Itab known to compilers 896 // allocated in non-garbage-collected memory 897 // Needs to be in sync with 898 // ../cmd/compile/internal/reflectdata/reflect.go:/^func.WriteTabs. 899 type itab struct { 900 inter *interfacetype 901 _type *_type 902 hash uint32 // copy of _type.hash. Used for type switches. 903 _ [4]byte 904 fun [1]uintptr // variable sized. fun[0]==0 means _type does not implement inter. 905 } 906 907 // Lock-free stack node. 908 // Also known to export_test.go. 909 type lfnode struct { 910 next uint64 911 pushcnt uintptr 912 } 913 914 type forcegcstate struct { 915 lock mutex 916 g *g 917 idle uint32 918 } 919 920 // extendRandom extends the random numbers in r[:n] to the whole slice r. 921 // Treats n<0 as n==0. 922 func extendRandom(r []byte, n int) { 923 if n < 0 { 924 n = 0 925 } 926 for n < len(r) { 927 // Extend random bits using hash function & time seed 928 w := n 929 if w > 16 { 930 w = 16 931 } 932 h := memhash(unsafe.Pointer(&r[n-w]), uintptr(nanotime()), uintptr(w)) 933 for i := 0; i < goarch.PtrSize && n < len(r); i++ { 934 r[n] = byte(h) 935 n++ 936 h >>= 8 937 } 938 } 939 } 940 941 // A _defer holds an entry on the list of deferred calls. 942 // If you add a field here, add code to clear it in freedefer and deferProcStack 943 // This struct must match the code in cmd/compile/internal/ssagen/ssa.go:deferstruct 944 // and cmd/compile/internal/ssagen/ssa.go:(*state).call. 945 // Some defers will be allocated on the stack and some on the heap. 946 // All defers are logically part of the stack, so write barriers to 947 // initialize them are not required. All defers must be manually scanned, 948 // and for heap defers, marked. 949 type _defer struct { 950 started bool 951 heap bool 952 // openDefer indicates that this _defer is for a frame with open-coded 953 // defers. We have only one defer record for the entire frame (which may 954 // currently have 0, 1, or more defers active). 955 openDefer bool 956 sp uintptr // sp at time of defer 957 pc uintptr // pc at time of defer 958 fn func() // can be nil for open-coded defers 959 _panic *_panic // panic that is running defer 960 link *_defer // next defer on G; can point to either heap or stack! 961 962 // If openDefer is true, the fields below record values about the stack 963 // frame and associated function that has the open-coded defer(s). sp 964 // above will be the sp for the frame, and pc will be address of the 965 // deferreturn call in the function. 966 fd unsafe.Pointer // funcdata for the function associated with the frame 967 varp uintptr // value of varp for the stack frame 968 // framepc is the current pc associated with the stack frame. Together, 969 // with sp above (which is the sp associated with the stack frame), 970 // framepc/sp can be used as pc/sp pair to continue a stack trace via 971 // gentraceback(). 972 framepc uintptr 973 } 974 975 // A _panic holds information about an active panic. 976 // 977 // A _panic value must only ever live on the stack. 978 // 979 // The argp and link fields are stack pointers, but don't need special 980 // handling during stack growth: because they are pointer-typed and 981 // _panic values only live on the stack, regular stack pointer 982 // adjustment takes care of them. 983 type _panic struct { 984 argp unsafe.Pointer // pointer to arguments of deferred call run during panic; cannot move - known to liblink 985 arg interface{} // argument to panic 986 link *_panic // link to earlier panic 987 pc uintptr // where to return to in runtime if this panic is bypassed 988 sp unsafe.Pointer // where to return to in runtime if this panic is bypassed 989 recovered bool // whether this panic is over 990 aborted bool // the panic was aborted 991 goexit bool 992 } 993 994 // stack traces 995 type stkframe struct { 996 fn funcInfo // function being run 997 pc uintptr // program counter within fn 998 continpc uintptr // program counter where execution can continue, or 0 if not 999 lr uintptr // program counter at caller aka link register 1000 sp uintptr // stack pointer at pc 1001 fp uintptr // stack pointer at caller aka frame pointer 1002 varp uintptr // top of local variables 1003 argp uintptr // pointer to function arguments 1004 arglen uintptr // number of bytes at argp 1005 argmap *bitvector // force use of this argmap 1006 } 1007 1008 // ancestorInfo records details of where a goroutine was started. 1009 type ancestorInfo struct { 1010 pcs []uintptr // pcs from the stack of this goroutine 1011 goid int64 // goroutine id of this goroutine; original goroutine possibly dead 1012 gopc uintptr // pc of go statement that created this goroutine 1013 } 1014 1015 const ( 1016 _TraceRuntimeFrames = 1 << iota // include frames for internal runtime functions. 1017 _TraceTrap // the initial PC, SP are from a trap, not a return PC from a call 1018 _TraceJumpStack // if traceback is on a systemstack, resume trace at g that called into it 1019 ) 1020 1021 // The maximum number of frames we print for a traceback 1022 const _TracebackMaxFrames = 100 1023 1024 // A waitReason explains why a goroutine has been stopped. 1025 // See gopark. Do not re-use waitReasons, add new ones. 1026 type waitReason uint8 1027 1028 const ( 1029 waitReasonZero waitReason = iota // "" 1030 waitReasonGCAssistMarking // "GC assist marking" 1031 waitReasonIOWait // "IO wait" 1032 waitReasonChanReceiveNilChan // "chan receive (nil chan)" 1033 waitReasonChanSendNilChan // "chan send (nil chan)" 1034 waitReasonDumpingHeap // "dumping heap" 1035 waitReasonGarbageCollection // "garbage collection" 1036 waitReasonGarbageCollectionScan // "garbage collection scan" 1037 waitReasonPanicWait // "panicwait" 1038 waitReasonSelect // "select" 1039 waitReasonSelectNoCases // "select (no cases)" 1040 waitReasonGCAssistWait // "GC assist wait" 1041 waitReasonGCSweepWait // "GC sweep wait" 1042 waitReasonGCScavengeWait // "GC scavenge wait" 1043 waitReasonChanReceive // "chan receive" 1044 waitReasonChanSend // "chan send" 1045 waitReasonFinalizerWait // "finalizer wait" 1046 waitReasonForceGCIdle // "force gc (idle)" 1047 waitReasonSemacquire // "semacquire" 1048 waitReasonSleep // "sleep" 1049 waitReasonSyncCondWait // "sync.Cond.Wait" 1050 waitReasonTimerGoroutineIdle // "timer goroutine (idle)" 1051 waitReasonTraceReaderBlocked // "trace reader (blocked)" 1052 waitReasonWaitForGCCycle // "wait for GC cycle" 1053 waitReasonGCWorkerIdle // "GC worker (idle)" 1054 waitReasonPreempted // "preempted" 1055 waitReasonDebugCall // "debug call" 1056 ) 1057 1058 var waitReasonStrings = [...]string{ 1059 waitReasonZero: "", 1060 waitReasonGCAssistMarking: "GC assist marking", 1061 waitReasonIOWait: "IO wait", 1062 waitReasonChanReceiveNilChan: "chan receive (nil chan)", 1063 waitReasonChanSendNilChan: "chan send (nil chan)", 1064 waitReasonDumpingHeap: "dumping heap", 1065 waitReasonGarbageCollection: "garbage collection", 1066 waitReasonGarbageCollectionScan: "garbage collection scan", 1067 waitReasonPanicWait: "panicwait", 1068 waitReasonSelect: "select", 1069 waitReasonSelectNoCases: "select (no cases)", 1070 waitReasonGCAssistWait: "GC assist wait", 1071 waitReasonGCSweepWait: "GC sweep wait", 1072 waitReasonGCScavengeWait: "GC scavenge wait", 1073 waitReasonChanReceive: "chan receive", 1074 waitReasonChanSend: "chan send", 1075 waitReasonFinalizerWait: "finalizer wait", 1076 waitReasonForceGCIdle: "force gc (idle)", 1077 waitReasonSemacquire: "semacquire", 1078 waitReasonSleep: "sleep", 1079 waitReasonSyncCondWait: "sync.Cond.Wait", 1080 waitReasonTimerGoroutineIdle: "timer goroutine (idle)", 1081 waitReasonTraceReaderBlocked: "trace reader (blocked)", 1082 waitReasonWaitForGCCycle: "wait for GC cycle", 1083 waitReasonGCWorkerIdle: "GC worker (idle)", 1084 waitReasonPreempted: "preempted", 1085 waitReasonDebugCall: "debug call", 1086 } 1087 1088 func (w waitReason) String() string { 1089 if w < 0 || w >= waitReason(len(waitReasonStrings)) { 1090 return "unknown wait reason" 1091 } 1092 return waitReasonStrings[w] 1093 } 1094 1095 var ( 1096 allm *m 1097 gomaxprocs int32 1098 ncpu int32 1099 forcegc forcegcstate 1100 sched schedt 1101 newprocs int32 1102 1103 // allpLock protects P-less reads and size changes of allp, idlepMask, 1104 // and timerpMask, and all writes to allp. 1105 allpLock mutex 1106 // len(allp) == gomaxprocs; may change at safe points, otherwise 1107 // immutable. 1108 allp []*p 1109 // Bitmask of Ps in _Pidle list, one bit per P. Reads and writes must 1110 // be atomic. Length may change at safe points. 1111 // 1112 // Each P must update only its own bit. In order to maintain 1113 // consistency, a P going idle must the idle mask simultaneously with 1114 // updates to the idle P list under the sched.lock, otherwise a racing 1115 // pidleget may clear the mask before pidleput sets the mask, 1116 // corrupting the bitmap. 1117 // 1118 // N.B., procresize takes ownership of all Ps in stopTheWorldWithSema. 1119 idlepMask pMask 1120 // Bitmask of Ps that may have a timer, one bit per P. Reads and writes 1121 // must be atomic. Length may change at safe points. 1122 timerpMask pMask 1123 1124 // Pool of GC parked background workers. Entries are type 1125 // *gcBgMarkWorkerNode. 1126 gcBgMarkWorkerPool lfstack 1127 1128 // Total number of gcBgMarkWorker goroutines. Protected by worldsema. 1129 gcBgMarkWorkerCount int32 1130 1131 // Information about what cpu features are available. 1132 // Packages outside the runtime should not use these 1133 // as they are not an external api. 1134 // Set on startup in asm_{386,amd64}.s 1135 processorVersionInfo uint32 1136 isIntel bool 1137 1138 goarm uint8 // set by cmd/link on arm systems 1139 ) 1140 1141 // Set by the linker so the runtime can determine the buildmode. 1142 var ( 1143 islibrary bool // -buildmode=c-shared 1144 isarchive bool // -buildmode=c-archive 1145 ) 1146 1147 // Must agree with internal/buildcfg.Experiment.FramePointer. 1148 const framepointer_enabled = GOARCH == "amd64" || GOARCH == "arm64"