Source file src/runtime/runtime2.go
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/abi" 9 "internal/chacha8rand" 10 "internal/goarch" 11 "internal/runtime/atomic" 12 "internal/runtime/sys" 13 "unsafe" 14 ) 15 16 // defined constants 17 const ( 18 // G status 19 // 20 // Beyond indicating the general state of a G, the G status 21 // acts like a lock on the goroutine's stack (and hence its 22 // ability to execute user code). 23 // 24 // If you add to this list, add to the list 25 // of "okay during garbage collection" status 26 // in mgcmark.go too. 27 // 28 // TODO(austin): The _Gscan bit could be much lighter-weight. 29 // For example, we could choose not to run _Gscanrunnable 30 // goroutines found in the run queue, rather than CAS-looping 31 // until they become _Grunnable. And transitions like 32 // _Gscanwaiting -> _Gscanrunnable are actually okay because 33 // they don't affect stack ownership. 34 35 // _Gidle means this goroutine was just allocated and has not 36 // yet been initialized. 37 _Gidle = iota // 0 38 39 // _Grunnable means this goroutine is on a run queue. It is 40 // not currently executing user code. The stack is not owned. 41 _Grunnable // 1 42 43 // _Grunning means this goroutine may execute user code. The 44 // stack is owned by this goroutine. It is not on a run queue. 45 // It is assigned an M (g.m is valid) and it usually has a P 46 // (g.m.p is valid), but there are small windows of time where 47 // it might not, namely upon entering and exiting _Gsyscall. 48 _Grunning // 2 49 50 // _Gsyscall means this goroutine is executing a system call. 51 // It is not executing user code. The stack is owned by this 52 // goroutine. It is not on a run queue. It is assigned an M. 53 // It may have a P attached, but it does not own it. Code 54 // executing in this state must not touch g.m.p. 55 _Gsyscall // 3 56 57 // _Gwaiting means this goroutine is blocked in the runtime. 58 // It is not executing user code. It is not on a run queue, 59 // but should be recorded somewhere (e.g., a channel wait 60 // queue) so it can be ready()d when necessary. The stack is 61 // not owned *except* that a channel operation may read or 62 // write parts of the stack under the appropriate channel 63 // lock. Otherwise, it is not safe to access the stack after a 64 // goroutine enters _Gwaiting (e.g., it may get moved). 65 _Gwaiting // 4 66 67 // _Gmoribund_unused is currently unused, but hardcoded in gdb 68 // scripts. 69 _Gmoribund_unused // 5 70 71 // _Gdead means this goroutine is currently unused. It may be 72 // just exited, on a free list, or just being initialized. It 73 // is not executing user code. It may or may not have a stack 74 // allocated. The G and its stack (if any) are owned by the M 75 // that is exiting the G or that obtained the G from the free 76 // list. 77 _Gdead // 6 78 79 // _Genqueue_unused is currently unused. 80 _Genqueue_unused // 7 81 82 // _Gcopystack means this goroutine's stack is being moved. It 83 // is not executing user code and is not on a run queue. The 84 // stack is owned by the goroutine that put it in _Gcopystack. 85 _Gcopystack // 8 86 87 // _Gpreempted means this goroutine stopped itself for a 88 // suspendG preemption. It is like _Gwaiting, but nothing is 89 // yet responsible for ready()ing it. Some suspendG must CAS 90 // the status to _Gwaiting to take responsibility for 91 // ready()ing this G. 92 _Gpreempted // 9 93 94 // _Gleaked represents a leaked goroutine caught by the GC. 95 _Gleaked // 10 96 97 // _Gdeadextra is a _Gdead goroutine that's attached to an extra M 98 // used for cgo callbacks. 99 _Gdeadextra // 11 100 101 // _Gscan combined with one of the above states other than 102 // _Grunning indicates that GC is scanning the stack. The 103 // goroutine is not executing user code and the stack is owned 104 // by the goroutine that set the _Gscan bit. 105 // 106 // _Gscanrunning is different: it is used to briefly block 107 // state transitions while GC signals the G to scan its own 108 // stack. This is otherwise like _Grunning. 109 // 110 // atomicstatus&~Gscan gives the state the goroutine will 111 // return to when the scan completes. 112 _Gscan = 0x1000 113 _Gscanrunnable = _Gscan + _Grunnable // 0x1001 114 _Gscanrunning = _Gscan + _Grunning // 0x1002 115 _Gscansyscall = _Gscan + _Gsyscall // 0x1003 116 _Gscanwaiting = _Gscan + _Gwaiting // 0x1004 117 _Gscanpreempted = _Gscan + _Gpreempted // 0x1009 118 _Gscanleaked = _Gscan + _Gleaked // 0x100a 119 _Gscandeadextra = _Gscan + _Gdeadextra // 0x100b 120 ) 121 122 const ( 123 // P status 124 125 // _Pidle means a P is not being used to run user code or the 126 // scheduler. Typically, it's on the idle P list and available 127 // to the scheduler, but it may just be transitioning between 128 // other states. 129 // 130 // The P is owned by the idle list or by whatever is 131 // transitioning its state. Its run queue is empty. 132 _Pidle = iota 133 134 // _Prunning means a P is owned by an M and is being used to 135 // run user code or the scheduler. Only the M that owns this P 136 // is allowed to change the P's status from _Prunning. The M 137 // may transition the P to _Pidle (if it has no more work to 138 // do), or _Pgcstop (to halt for the GC). The M may also hand 139 // ownership of the P off directly to another M (for example, 140 // to schedule a locked G). 141 _Prunning 142 143 // _Psyscall_unused is a now-defunct state for a P. A P is 144 // identified as "in a system call" by looking at the goroutine's 145 // state. 146 _Psyscall_unused 147 148 // _Pgcstop means a P is halted for STW and owned by the M 149 // that stopped the world. The M that stopped the world 150 // continues to use its P, even in _Pgcstop. Transitioning 151 // from _Prunning to _Pgcstop causes an M to release its P and 152 // park. 153 // 154 // The P retains its run queue and startTheWorld will restart 155 // the scheduler on Ps with non-empty run queues. 156 _Pgcstop 157 158 // _Pdead means a P is no longer used (GOMAXPROCS shrank). We 159 // reuse Ps if GOMAXPROCS increases. A dead P is mostly 160 // stripped of its resources, though a few things remain 161 // (e.g., trace buffers). 162 _Pdead 163 ) 164 165 // Mutual exclusion locks. In the uncontended case, 166 // as fast as spin locks (just a few user-level instructions), 167 // but on the contention path they sleep in the kernel. 168 // A zeroed Mutex is unlocked (no need to initialize each lock). 169 // Initialization is helpful for static lock ranking, but not required. 170 type mutex struct { 171 // Empty struct if lock ranking is disabled, otherwise includes the lock rank 172 lockRankStruct 173 // Futex-based impl treats it as uint32 key, 174 // while sema-based impl as M* waitm. 175 // Used to be a union, but unions break precise GC. 176 key uintptr 177 } 178 179 type funcval struct { 180 fn uintptr 181 // variable-size, fn-specific data here 182 } 183 184 type iface struct { 185 tab *itab 186 data unsafe.Pointer 187 } 188 189 type eface struct { 190 _type *_type 191 data unsafe.Pointer 192 } 193 194 func efaceOf(ep *any) *eface { 195 return (*eface)(unsafe.Pointer(ep)) 196 } 197 198 // The guintptr, muintptr, and puintptr are all used to bypass write barriers. 199 // It is particularly important to avoid write barriers when the current P has 200 // been released, because the GC thinks the world is stopped, and an 201 // unexpected write barrier would not be synchronized with the GC, 202 // which can lead to a half-executed write barrier that has marked the object 203 // but not queued it. If the GC skips the object and completes before the 204 // queuing can occur, it will incorrectly free the object. 205 // 206 // We tried using special assignment functions invoked only when not 207 // holding a running P, but then some updates to a particular memory 208 // word went through write barriers and some did not. This breaks the 209 // write barrier shadow checking mode, and it is also scary: better to have 210 // a word that is completely ignored by the GC than to have one for which 211 // only a few updates are ignored. 212 // 213 // Gs and Ps are always reachable via true pointers in the 214 // allgs and allp lists or (during allocation before they reach those lists) 215 // from stack variables. 216 // 217 // Ms are always reachable via true pointers either from allm or 218 // freem. Unlike Gs and Ps we do free Ms, so it's important that 219 // nothing ever hold an muintptr across a safe point. 220 221 // A guintptr holds a goroutine pointer, but typed as a uintptr 222 // to bypass write barriers. It is used in the Gobuf goroutine state 223 // and in scheduling lists that are manipulated without a P. 224 // 225 // The Gobuf.g goroutine pointer is almost always updated by assembly code. 226 // In one of the few places it is updated by Go code - func save - it must be 227 // treated as a uintptr to avoid a write barrier being emitted at a bad time. 228 // Instead of figuring out how to emit the write barriers missing in the 229 // assembly manipulation, we change the type of the field to uintptr, 230 // so that it does not require write barriers at all. 231 // 232 // Goroutine structs are published in the allg list and never freed. 233 // That will keep the goroutine structs from being collected. 234 // There is never a time that Gobuf.g's contain the only references 235 // to a goroutine: the publishing of the goroutine in allg comes first. 236 // Goroutine pointers are also kept in non-GC-visible places like TLS, 237 // so I can't see them ever moving. If we did want to start moving data 238 // in the GC, we'd need to allocate the goroutine structs from an 239 // alternate arena. Using guintptr doesn't make that problem any worse. 240 // Note that pollDesc.rg, pollDesc.wg also store g in uintptr form, 241 // so they would need to be updated too if g's start moving. 242 type guintptr uintptr 243 244 //go:nosplit 245 func (gp guintptr) ptr() *g { return (*g)(unsafe.Pointer(gp)) } 246 247 //go:nosplit 248 func (gp *guintptr) set(g *g) { *gp = guintptr(unsafe.Pointer(g)) } 249 250 //go:nosplit 251 func (gp *guintptr) cas(old, new guintptr) bool { 252 return atomic.Casuintptr((*uintptr)(unsafe.Pointer(gp)), uintptr(old), uintptr(new)) 253 } 254 255 //go:nosplit 256 func (gp *g) guintptr() guintptr { 257 return guintptr(unsafe.Pointer(gp)) 258 } 259 260 // setGNoWB performs *gp = new without a write barrier. 261 // For times when it's impractical to use a guintptr. 262 // 263 //go:nosplit 264 //go:nowritebarrier 265 func setGNoWB(gp **g, new *g) { 266 (*guintptr)(unsafe.Pointer(gp)).set(new) 267 } 268 269 type puintptr uintptr 270 271 //go:nosplit 272 func (pp puintptr) ptr() *p { return (*p)(unsafe.Pointer(pp)) } 273 274 //go:nosplit 275 func (pp *puintptr) set(p *p) { *pp = puintptr(unsafe.Pointer(p)) } 276 277 // muintptr is a *m that is not tracked by the garbage collector. 278 // 279 // Because we do free Ms, there are some additional constrains on 280 // muintptrs: 281 // 282 // 1. Never hold an muintptr locally across a safe point. 283 // 284 // 2. Any muintptr in the heap must be owned by the M itself so it can 285 // ensure it is not in use when the last true *m is released. 286 type muintptr uintptr 287 288 //go:nosplit 289 func (mp muintptr) ptr() *m { return (*m)(unsafe.Pointer(mp)) } 290 291 //go:nosplit 292 func (mp *muintptr) set(m *m) { *mp = muintptr(unsafe.Pointer(m)) } 293 294 // setMNoWB performs *mp = new without a write barrier. 295 // For times when it's impractical to use an muintptr. 296 // 297 //go:nosplit 298 //go:nowritebarrier 299 func setMNoWB(mp **m, new *m) { 300 (*muintptr)(unsafe.Pointer(mp)).set(new) 301 } 302 303 type gobuf struct { 304 // ctxt is unusual with respect to GC: it may be a 305 // heap-allocated funcval, so GC needs to track it, but it 306 // needs to be set and cleared from assembly, where it's 307 // difficult to have write barriers. However, ctxt is really a 308 // saved, live register, and we only ever exchange it between 309 // the real register and the gobuf. Hence, we treat it as a 310 // root during stack scanning, which means assembly that saves 311 // and restores it doesn't need write barriers. It's still 312 // typed as a pointer so that any other writes from Go get 313 // write barriers. 314 sp uintptr 315 pc uintptr 316 g guintptr 317 ctxt unsafe.Pointer 318 lr uintptr 319 bp uintptr // for framepointer-enabled architectures 320 } 321 322 // maybeTraceablePtr is a special pointer that is conditionally trackable 323 // by the GC. It consists of an address as a uintptr (vu) and a pointer 324 // to a data element (vp). 325 // 326 // maybeTraceablePtr values can be in one of three states: 327 // 1. Unset: vu == 0 && vp == nil 328 // 2. Untracked: vu != 0 && vp == nil 329 // 3. Tracked: vu != 0 && vp != nil 330 // 331 // Do not set fields manually. Use methods instead. 332 // Extend this type with additional methods if needed. 333 type maybeTraceablePtr struct { 334 vp unsafe.Pointer // For liveness only. 335 vu uintptr // Source of truth. 336 } 337 338 // untrack unsets the pointer but preserves the address. 339 // This is used to hide the pointer from the GC. 340 // 341 //go:nosplit 342 func (p *maybeTraceablePtr) setUntraceable() { 343 p.vp = nil 344 } 345 346 // setTraceable resets the pointer to the stored address. 347 // This is used to make the pointer visible to the GC. 348 // 349 //go:nosplit 350 func (p *maybeTraceablePtr) setTraceable() { 351 p.vp = unsafe.Pointer(p.vu) 352 } 353 354 // set sets the pointer to the data element and updates the address. 355 // 356 //go:nosplit 357 func (p *maybeTraceablePtr) set(v unsafe.Pointer) { 358 p.vp = v 359 p.vu = uintptr(v) 360 } 361 362 // get retrieves the pointer to the data element. 363 // 364 //go:nosplit 365 func (p *maybeTraceablePtr) get() unsafe.Pointer { 366 return unsafe.Pointer(p.vu) 367 } 368 369 // uintptr returns the uintptr address of the pointer. 370 // 371 //go:nosplit 372 func (p *maybeTraceablePtr) uintptr() uintptr { 373 return p.vu 374 } 375 376 // maybeTraceableChan extends conditionally trackable pointers (maybeTraceablePtr) 377 // to track hchan pointers. 378 // 379 // Do not set fields manually. Use methods instead. 380 type maybeTraceableChan struct { 381 maybeTraceablePtr 382 } 383 384 //go:nosplit 385 func (p *maybeTraceableChan) set(c *hchan) { 386 p.maybeTraceablePtr.set(unsafe.Pointer(c)) 387 } 388 389 //go:nosplit 390 func (p *maybeTraceableChan) get() *hchan { 391 return (*hchan)(p.maybeTraceablePtr.get()) 392 } 393 394 // sudog (pseudo-g) represents a g in a wait list, such as for sending/receiving 395 // on a channel. 396 // 397 // sudog is necessary because the g ↔ synchronization object relation 398 // is many-to-many. A g can be on many wait lists, so there may be 399 // many sudogs for one g; and many gs may be waiting on the same 400 // synchronization object, so there may be many sudogs for one object. 401 // 402 // sudogs are allocated from a special pool. Use acquireSudog and 403 // releaseSudog to allocate and free them. 404 type sudog struct { 405 // The following fields are protected by the hchan.lock of the 406 // channel this sudog is blocking on. shrinkstack depends on 407 // this for sudogs involved in channel ops. 408 409 g *g 410 411 next *sudog 412 prev *sudog 413 414 elem maybeTraceablePtr // data element (may point to stack) 415 416 // The following fields are never accessed concurrently. 417 // For channels, waitlink is only accessed by g. 418 // For semaphores, all fields (including the ones above) 419 // are only accessed when holding a semaRoot lock. 420 421 acquiretime int64 422 releasetime int64 423 ticket uint32 424 425 // isSelect indicates g is participating in a select, so 426 // g.selectDone must be CAS'd to win the wake-up race. 427 isSelect bool 428 429 // success indicates whether communication over channel c 430 // succeeded. It is true if the goroutine was awoken because a 431 // value was delivered over channel c, and false if awoken 432 // because c was closed. 433 success bool 434 435 // waiters is a count of semaRoot waiting list other than head of list, 436 // clamped to a uint16 to fit in unused space. 437 // Only meaningful at the head of the list. 438 // (If we wanted to be overly clever, we could store a high 16 bits 439 // in the second entry in the list.) 440 waiters uint16 441 442 parent *sudog // semaRoot binary tree 443 waitlink *sudog // g.waiting list or semaRoot 444 waittail *sudog // semaRoot 445 c maybeTraceableChan // channel 446 } 447 448 type libcall struct { 449 fn uintptr 450 n uintptr // number of parameters 451 args uintptr // parameters 452 r1 uintptr // return values 453 r2 uintptr 454 err uintptr // error number 455 } 456 457 // Stack describes a Go execution stack. 458 // The bounds of the stack are exactly [lo, hi), 459 // with no implicit data structures on either side. 460 type stack struct { 461 lo uintptr 462 hi uintptr 463 } 464 465 // heldLockInfo gives info on a held lock and the rank of that lock 466 type heldLockInfo struct { 467 lockAddr uintptr 468 rank lockRank 469 } 470 471 type g struct { 472 // Stack parameters. 473 // stack describes the actual stack memory: [stack.lo, stack.hi). 474 // stackguard0 is the stack pointer compared in the Go stack growth prologue. 475 // It is stack.lo+StackGuard normally, but can be StackPreempt to trigger a preemption. 476 // stackguard1 is the stack pointer compared in the //go:systemstack stack growth prologue. 477 // It is stack.lo+StackGuard on g0 and gsignal stacks. 478 // It is ~0 on other goroutine stacks, to trigger a call to morestackc (and crash). 479 stack stack // offset known to runtime/cgo 480 stackguard0 uintptr // offset known to cmd/internal/obj/* 481 stackguard1 uintptr // offset known to cmd/internal/obj/* 482 483 _panic *_panic // innermost panic 484 _defer *_defer // innermost defer 485 m *m // current m 486 sched gobuf 487 syscallsp uintptr // if status==Gsyscall, syscallsp = sched.sp to use during gc 488 syscallpc uintptr // if status==Gsyscall, syscallpc = sched.pc to use during gc 489 syscallbp uintptr // if status==Gsyscall, syscallbp = sched.bp to use in fpTraceback 490 stktopsp uintptr // expected sp at top of stack, to check in traceback 491 // param is a generic pointer parameter field used to pass 492 // values in particular contexts where other storage for the 493 // parameter would be difficult to find. It is currently used 494 // in four ways: 495 // 1. When a channel operation wakes up a blocked goroutine, it sets param to 496 // point to the sudog of the completed blocking operation. 497 // 2. By gcAssistAlloc1 to signal back to its caller that the goroutine completed 498 // the GC cycle. It is unsafe to do so in any other way, because the goroutine's 499 // stack may have moved in the meantime. 500 // 3. By debugCallWrap to pass parameters to a new goroutine because allocating a 501 // closure in the runtime is forbidden. 502 // 4. When a panic is recovered and control returns to the respective frame, 503 // param may point to a savedOpenDeferState. 504 param unsafe.Pointer 505 atomicstatus atomic.Uint32 506 stackLock uint32 // sigprof/scang lock; TODO: fold in to atomicstatus 507 goid uint64 508 schedlink guintptr 509 waitsince int64 // approx time when the g become blocked 510 waitreason waitReason // if status==Gwaiting 511 512 preempt bool // preemption signal, duplicates stackguard0 = stackpreempt 513 preemptStop bool // transition to _Gpreempted on preemption; otherwise, just deschedule 514 preemptShrink bool // shrink stack at synchronous safe point 515 516 // asyncSafePoint is set if g is stopped at an asynchronous 517 // safe point. This means there are frames on the stack 518 // without precise pointer information. 519 asyncSafePoint bool 520 521 paniconfault bool // panic (instead of crash) on unexpected fault address 522 gcscandone bool // g has scanned stack; protected by _Gscan bit in status 523 throwsplit bool // must not split stack 524 // activeStackChans indicates that there are unlocked channels 525 // pointing into this goroutine's stack. If true, stack 526 // copying needs to acquire channel locks to protect these 527 // areas of the stack. 528 activeStackChans bool 529 // parkingOnChan indicates that the goroutine is about to 530 // park on a chansend or chanrecv. Used to signal an unsafe point 531 // for stack shrinking. 532 parkingOnChan atomic.Bool 533 // inMarkAssist indicates whether the goroutine is in mark assist. 534 // Used by the execution tracer. 535 inMarkAssist bool 536 coroexit bool // argument to coroswitch_m 537 538 raceignore int8 // ignore race detection events 539 nocgocallback bool // whether disable callback from C 540 tracking bool // whether we're tracking this G for sched latency statistics 541 trackingSeq uint8 // used to decide whether to track this G 542 trackingStamp int64 // timestamp of when the G last started being tracked 543 runnableTime int64 // the amount of time spent runnable, cleared when running, only used when tracking 544 lockedm muintptr 545 fipsIndicator uint8 546 fipsOnlyBypass bool 547 ditWanted bool // set if g wants to be executed with DIT enabled 548 syncSafePoint bool // set if g is stopped at a synchronous safe point. 549 runningCleanups atomic.Bool 550 sig uint32 551 secret int32 // current nesting of runtime/secret.Do calls. 552 writebuf []byte 553 sigcode0 uintptr 554 sigcode1 uintptr 555 sigpc uintptr 556 parentGoid uint64 // goid of goroutine that created this goroutine 557 gopc uintptr // pc of go statement that created this goroutine 558 ancestors *[]ancestorInfo // ancestor information goroutine(s) that created this goroutine (only used if debug.tracebackancestors) 559 startpc uintptr // pc of goroutine function 560 racectx uintptr 561 waiting *sudog // sudog structures this g is waiting on (that have a valid elem ptr); in lock order 562 cgoCtxt []uintptr // cgo traceback context 563 labels unsafe.Pointer // profiler labels 564 timer *timer // cached timer for time.Sleep 565 sleepWhen int64 // when to sleep until 566 selectDone atomic.Uint32 // are we participating in a select and did someone win the race? 567 568 // goroutineProfiled indicates the status of this goroutine's stack for the 569 // current in-progress goroutine profile 570 goroutineProfiled goroutineProfileStateHolder 571 572 coroarg *coro // argument during coroutine transfers 573 bubble *synctestBubble 574 575 // xRegs stores the extended register state if this G has been 576 // asynchronously preempted. 577 xRegs xRegPerG 578 579 // Per-G tracer state. 580 trace gTraceState 581 582 // Per-G GC state 583 584 // gcAssistBytes is this G's GC assist credit in terms of 585 // bytes allocated. If this is positive, then the G has credit 586 // to allocate gcAssistBytes bytes without assisting. If this 587 // is negative, then the G must correct this by performing 588 // scan work. We track this in bytes to make it fast to update 589 // and check for debt in the malloc hot path. The assist ratio 590 // determines how this corresponds to scan work debt. 591 gcAssistBytes int64 592 593 // valgrindStackID is used to track what memory is used for stacks when a program is 594 // built with the "valgrind" build tag, otherwise it is unused. 595 valgrindStackID uintptr 596 } 597 598 // gTrackingPeriod is the number of transitions out of _Grunning between 599 // latency tracking runs. 600 const gTrackingPeriod = 8 601 602 const ( 603 // tlsSlots is the number of pointer-sized slots reserved for TLS on some platforms, 604 // like Windows. 605 tlsSlots = 6 606 tlsSize = tlsSlots * goarch.PtrSize 607 ) 608 609 // Values for m.freeWait. 610 const ( 611 freeMStack = 0 // M done, free stack and reference. 612 freeMRef = 1 // M done, free reference. 613 freeMWait = 2 // M still in use. 614 ) 615 616 type m struct { 617 g0 *g // goroutine with scheduling stack 618 morebuf gobuf // gobuf arg to morestack 619 divmod uint32 // div/mod denominator for arm - known to liblink (cmd/internal/obj/arm/obj5.go) 620 621 // Fields whose offsets are not known to debuggers. 622 623 procid uint64 // for debuggers, but offset not hard-coded 624 gsignal *g // signal-handling g 625 goSigStack gsignalStack // Go-allocated signal handling stack 626 sigmask sigset // storage for saved signal mask 627 tls [tlsSlots]uintptr // thread-local storage (for x86 extern register) 628 mstartfn func() 629 curg *g // current running goroutine 630 caughtsig guintptr // goroutine running during fatal signal 631 632 // Indicates whether we've received a signal while 633 // running in secret mode. 634 signalSecret bool 635 636 // p is the currently attached P for executing Go code, nil if not executing user Go code. 637 // 638 // A non-nil p implies exclusive ownership of the P, unless curg is in _Gsyscall. 639 // In _Gsyscall the scheduler may mutate this instead. The point of synchronization 640 // is the _Gscan bit on curg's status. The scheduler must arrange to prevent curg 641 // from transitioning out of _Gsyscall if it intends to mutate p. 642 p puintptr 643 644 nextp puintptr // The next P to install before executing. Implies exclusive ownership of this P. 645 oldp puintptr // The P that was attached before executing a syscall. 646 id int64 647 mallocing int32 648 throwing throwType 649 preemptoff string // if != "", keep curg running on this m 650 locks int32 651 dying int32 652 profilehz int32 653 spinning bool // m is out of work and is actively looking for work 654 blocked bool // m is blocked on a note 655 newSigstack bool // minit on C thread called sigaltstack 656 printlock int8 657 incgo bool // m is executing a cgo call 658 isextra bool // m is an extra m 659 isExtraInC bool // m is an extra m that does not have any Go frames 660 isExtraInSig bool // m is an extra m in a signal handler 661 freeWait atomic.Uint32 // Whether it is safe to free g0 and delete m (one of freeMRef, freeMStack, freeMWait) 662 needextram bool 663 g0StackAccurate bool // whether the g0 stack has accurate bounds 664 traceback uint8 665 allpSnapshot []*p // Snapshot of allp for use after dropping P in findRunnable, nil otherwise. 666 ncgocall uint64 // number of cgo calls in total 667 ncgo int32 // number of cgo calls currently in progress 668 cgoCallersUse atomic.Uint32 // if non-zero, cgoCallers in use temporarily 669 cgoCallers *cgoCallers // cgo traceback if crashing in cgo call 670 park note 671 alllink *m // on allm 672 schedlink muintptr 673 idleNode listNodeManual 674 lockedg guintptr 675 createstack [32]uintptr // stack that created this thread, it's used for StackRecord.Stack0, so it must align with it. 676 lockedExt uint32 // tracking for external LockOSThread 677 lockedInt uint32 // tracking for internal lockOSThread 678 mWaitList mWaitList // list of runtime lock waiters 679 ditEnabled bool // set if DIT is currently enabled on this M 680 681 mLockProfile mLockProfile // fields relating to runtime.lock contention 682 profStack []uintptr // used for memory/block/mutex stack traces 683 684 // wait* are used to carry arguments from gopark into park_m, because 685 // there's no stack to put them on. That is their sole purpose. 686 waitunlockf func(*g, unsafe.Pointer) bool 687 waitlock unsafe.Pointer 688 waitTraceSkip int 689 waitTraceBlockReason traceBlockReason 690 691 syscalltick uint32 692 freelink *m // on sched.freem 693 trace mTraceState 694 695 // These are here to avoid using the G stack so the stack can move during the call. 696 libcallpc uintptr // for cpu profiler 697 libcallsp uintptr 698 libcallg guintptr 699 winsyscall winlibcall // stores syscall parameters on windows 700 701 vdsoSP uintptr // SP for traceback while in VDSO call (0 if not in call) 702 vdsoPC uintptr // PC for traceback while in VDSO call 703 704 // preemptGen counts the number of completed preemption 705 // signals. This is used to detect when a preemption is 706 // requested, but fails. 707 preemptGen atomic.Uint32 708 709 // Whether this is a pending preemption signal on this M. 710 signalPending atomic.Uint32 711 712 // pcvalue lookup cache 713 pcvalueCache pcvalueCache 714 715 dlogPerM 716 717 mOS 718 719 chacha8 chacha8rand.State 720 cheaprand uint32 721 cheaprand64 uint64 722 723 // Up to 10 locks held by this m, maintained by the lock ranking code. 724 locksHeldLen int 725 locksHeld [10]heldLockInfo 726 727 // self points this M until mexit clears it to return nil. 728 self mWeakPointer 729 } 730 731 const mRedZoneSize = (16 << 3) * asanenabledBit // redZoneSize(2048) 732 733 type mPadded struct { 734 m 735 736 // Size the runtime.m structure so it fits in the 2048-byte size class, and 737 // not in the next-smallest (1792-byte) size class. That leaves the 11 low 738 // bits of muintptr values available for flags, as required by 739 // lock_spinbit.go. 740 _ [(1 - goarch.IsWasm) * (2048 - mallocHeaderSize - mRedZoneSize - unsafe.Sizeof(m{}))]byte 741 } 742 743 // mWeakPointer is a "weak" pointer to an M. A weak pointer for each M is 744 // available as m.self. Users may copy mWeakPointer arbitrarily, and get will 745 // return the M if it is still live, or nil after mexit. 746 // 747 // The zero value is treated as a nil pointer. 748 // 749 // Note that get may race with M exit. A successful get will keep the m object 750 // alive, but the M itself may be exited and thus not actually usable. 751 type mWeakPointer struct { 752 m *atomic.Pointer[m] 753 } 754 755 func newMWeakPointer(mp *m) mWeakPointer { 756 w := mWeakPointer{m: new(atomic.Pointer[m])} 757 w.m.Store(mp) 758 return w 759 } 760 761 func (w mWeakPointer) get() *m { 762 if w.m == nil { 763 return nil 764 } 765 return w.m.Load() 766 } 767 768 // clear sets the weak pointer to nil. It cannot be used on zero value 769 // mWeakPointers. 770 func (w mWeakPointer) clear() { 771 w.m.Store(nil) 772 } 773 774 type p struct { 775 id int32 776 status uint32 // one of pidle/prunning/... 777 link puintptr 778 schedtick uint32 // incremented on every scheduler call 779 syscalltick uint32 // incremented on every system call 780 sysmontick sysmontick // last tick observed by sysmon 781 m muintptr // back-link to associated m (nil if idle) 782 mcache *mcache 783 pcache pageCache 784 raceprocctx uintptr 785 786 // oldm is the previous m this p ran on. 787 // 788 // We are not assosciated with this m, so we have no control over its 789 // lifecycle. This value is an m.self object which points to the m 790 // until the m exits. 791 // 792 // Note that this m may be idle, running, or exiting. It should only be 793 // used with mgetSpecific, which will take ownership of the m only if 794 // it is idle. 795 oldm mWeakPointer 796 797 deferpool []*_defer // pool of available defer structs (see panic.go) 798 deferpoolbuf [32]*_defer 799 800 // Cache of goroutine ids, amortizes accesses to runtime·sched.goidgen. 801 goidcache uint64 802 goidcacheend uint64 803 804 // Queue of runnable goroutines. Accessed without lock. 805 runqhead uint32 806 runqtail uint32 807 runq [256]guintptr 808 // runnext, if non-nil, is a runnable G that was ready'd by 809 // the current G and should be run next instead of what's in 810 // runq if there's time remaining in the running G's time 811 // slice. It will inherit the time left in the current time 812 // slice. If a set of goroutines is locked in a 813 // communicate-and-wait pattern, this schedules that set as a 814 // unit and eliminates the (potentially large) scheduling 815 // latency that otherwise arises from adding the ready'd 816 // goroutines to the end of the run queue. 817 // 818 // Note that while other P's may atomically CAS this to zero, 819 // only the owner P can CAS it to a valid G. 820 runnext guintptr 821 822 // Available G's (status == Gdead) 823 gFree gList 824 825 sudogcache []*sudog 826 sudogbuf [128]*sudog 827 828 // Cache of mspan objects from the heap. 829 mspancache struct { 830 // We need an explicit length here because this field is used 831 // in allocation codepaths where write barriers are not allowed, 832 // and eliminating the write barrier/keeping it eliminated from 833 // slice updates is tricky, more so than just managing the length 834 // ourselves. 835 len int 836 buf [128]*mspan 837 } 838 839 // Cache of a single pinner object to reduce allocations from repeated 840 // pinner creation. 841 pinnerCache *pinner 842 843 trace pTraceState 844 845 palloc persistentAlloc // per-P to avoid mutex 846 847 // Per-P GC state 848 gcAssistTime int64 // Nanoseconds in assistAlloc 849 gcFractionalMarkTime atomic.Int64 // Nanoseconds in fractional mark worker 850 851 // limiterEvent tracks events for the GC CPU limiter. 852 limiterEvent limiterEvent 853 854 // gcMarkWorkerMode is the mode for the next mark worker to run in. 855 // That is, this is used to communicate with the worker goroutine 856 // selected for immediate execution by 857 // gcController.findRunnableGCWorker. When scheduling other goroutines, 858 // this field must be set to gcMarkWorkerNotWorker. 859 gcMarkWorkerMode gcMarkWorkerMode 860 // gcMarkWorkerStartTime is the nanotime() at which the most recent 861 // mark worker started. 862 gcMarkWorkerStartTime int64 863 864 // nextGCMarkWorker is the next mark worker to run. This may be set 865 // during start-the-world to assign a worker to this P. The P runs this 866 // worker on the next call to gcController.findRunnableGCWorker. If the 867 // P runs something else or stops, it must release this worker via 868 // gcController.releaseNextGCMarkWorker. 869 // 870 // See comment in gcBgMarkWorker about the lifetime of 871 // gcBgMarkWorkerNode. 872 // 873 // Only accessed by this P or during STW. 874 nextGCMarkWorker *gcBgMarkWorkerNode 875 876 // gcw is this P's GC work buffer cache. The work buffer is 877 // filled by write barriers, drained by mutator assists, and 878 // disposed on certain GC state transitions. 879 gcw gcWork 880 881 // wbBuf is this P's GC write barrier buffer. 882 // 883 // TODO: Consider caching this in the running G. 884 wbBuf wbBuf 885 886 runSafePointFn uint32 // if 1, run sched.safePointFn at next safe point 887 888 // statsSeq is a counter indicating whether this P is currently 889 // writing any stats. Its value is even when not, odd when it is. 890 statsSeq atomic.Uint32 891 892 // Timer heap. 893 timers timers 894 895 // Cleanups. 896 cleanups *cleanupBlock 897 cleanupsQueued uint64 // monotonic count of cleanups queued by this P 898 899 // maxStackScanDelta accumulates the amount of stack space held by 900 // live goroutines (i.e. those eligible for stack scanning). 901 // Flushed to gcController.maxStackScan once maxStackScanSlack 902 // or -maxStackScanSlack is reached. 903 maxStackScanDelta int64 904 905 // gc-time statistics about current goroutines 906 // Note that this differs from maxStackScan in that this 907 // accumulates the actual stack observed to be used at GC time (hi - sp), 908 // not an instantaneous measure of the total stack size that might need 909 // to be scanned (hi - lo). 910 scannedStackSize uint64 // stack size of goroutines scanned by this P 911 scannedStacks uint64 // number of goroutines scanned by this P 912 913 // preempt is set to indicate that this P should be enter the 914 // scheduler ASAP (regardless of what G is running on it). 915 preempt bool 916 917 // gcStopTime is the nanotime timestamp that this P last entered _Pgcstop. 918 gcStopTime int64 919 920 // goroutinesCreated is the total count of goroutines created by this P. 921 goroutinesCreated uint64 922 923 // xRegs is the per-P extended register state used by asynchronous 924 // preemption. This is an empty struct on platforms that don't use extended 925 // register state. 926 xRegs xRegPerP 927 928 // Padding is no longer needed. False sharing is now not a worry because p is large enough 929 // that its size class is an integer multiple of the cache line size (for any of our architectures). 930 } 931 932 type schedt struct { 933 goidgen atomic.Uint64 934 lastpoll atomic.Int64 // time of last network poll, 0 if currently polling 935 pollUntil atomic.Int64 // time to which current poll is sleeping 936 pollingNet atomic.Int32 // 1 if some P doing non-blocking network poll 937 938 lock mutex 939 940 // When increasing nmidle, nmidlelocked, nmsys, or nmfreed, be 941 // sure to call checkdead(). 942 943 midle listHeadManual // idle m's waiting for work 944 nmidle int32 // number of idle m's waiting for work 945 nmidlelocked int32 // number of locked m's waiting for work 946 mnext int64 // number of m's that have been created and next M ID 947 maxmcount int32 // maximum number of m's allowed (or die) 948 nmsys int32 // number of system m's not counted for deadlock 949 nmfreed int64 // cumulative number of freed m's 950 951 ngsys atomic.Int32 // number of system goroutines 952 nGsyscallNoP atomic.Int32 // number of goroutines in syscalls without a P but whose M is not isExtraInC 953 954 pidle puintptr // idle p's 955 npidle atomic.Int32 956 nmspinning atomic.Int32 // See "Worker thread parking/unparking" comment in proc.go. 957 needspinning atomic.Uint32 // See "Delicate dance" comment in proc.go. Boolean. Must hold sched.lock to set to 1. 958 959 // Global runnable queue. 960 runq gQueue 961 962 // disable controls selective disabling of the scheduler. 963 // 964 // Use schedEnableUser to control this. 965 // 966 // disable is protected by sched.lock. 967 disable struct { 968 // user disables scheduling of user goroutines. 969 user bool 970 runnable gQueue // pending runnable Gs 971 } 972 973 // Global cache of dead G's. 974 gFree struct { 975 lock mutex 976 stack gList // Gs with stacks 977 noStack gList // Gs without stacks 978 } 979 980 // Central cache of sudog structs. 981 sudoglock mutex 982 sudogcache *sudog 983 984 // Central pool of available defer structs. 985 deferlock mutex 986 deferpool *_defer 987 988 // freem is the list of m's waiting to be freed when their 989 // m.exited is set. Linked through m.freelink. 990 freem *m 991 992 gcwaiting atomic.Bool // gc is waiting to run 993 stopwait int32 994 stopnote note 995 sysmonwait atomic.Bool 996 sysmonnote note 997 998 // safePointFn should be called on each P at the next GC 999 // safepoint if p.runSafePointFn is set. 1000 safePointFn func(*p) 1001 safePointWait int32 1002 safePointNote note 1003 1004 profilehz int32 // cpu profiling rate 1005 1006 procresizetime int64 // nanotime() of last change to gomaxprocs 1007 totaltime int64 // ∫gomaxprocs dt up to procresizetime 1008 1009 customGOMAXPROCS bool // GOMAXPROCS was manually set from the environment or runtime.GOMAXPROCS 1010 1011 // sysmonlock protects sysmon's actions on the runtime. 1012 // 1013 // Acquire and hold this mutex to block sysmon from interacting 1014 // with the rest of the runtime. 1015 sysmonlock mutex 1016 1017 // timeToRun is a distribution of scheduling latencies, defined 1018 // as the sum of time a G spends in the _Grunnable state before 1019 // it transitions to _Grunning. 1020 timeToRun timeHistogram 1021 1022 // idleTime is the total CPU time Ps have "spent" idle. 1023 // 1024 // Reset on each GC cycle. 1025 idleTime atomic.Int64 1026 1027 // totalMutexWaitTime is the sum of time goroutines have spent in _Gwaiting 1028 // with a waitreason of the form waitReasonSync{RW,}Mutex{R,}Lock. 1029 totalMutexWaitTime atomic.Int64 1030 1031 // stwStoppingTimeGC/Other are distributions of stop-the-world stopping 1032 // latencies, defined as the time taken by stopTheWorldWithSema to get 1033 // all Ps to stop. stwStoppingTimeGC covers all GC-related STWs, 1034 // stwStoppingTimeOther covers the others. 1035 stwStoppingTimeGC timeHistogram 1036 stwStoppingTimeOther timeHistogram 1037 1038 // stwTotalTimeGC/Other are distributions of stop-the-world total 1039 // latencies, defined as the total time from stopTheWorldWithSema to 1040 // startTheWorldWithSema. This is a superset of 1041 // stwStoppingTimeGC/Other. stwTotalTimeGC covers all GC-related STWs, 1042 // stwTotalTimeOther covers the others. 1043 stwTotalTimeGC timeHistogram 1044 stwTotalTimeOther timeHistogram 1045 1046 // totalRuntimeLockWaitTime (plus the value of lockWaitTime on each M in 1047 // allm) is the sum of time goroutines have spent in _Grunnable and with an 1048 // M, but waiting for locks within the runtime. This field stores the value 1049 // for Ms that have exited. 1050 totalRuntimeLockWaitTime atomic.Int64 1051 1052 // goroutinesCreated (plus the value of goroutinesCreated on each P in allp) 1053 // is the sum of all goroutines created by the program. 1054 goroutinesCreated atomic.Uint64 1055 } 1056 1057 // Values for the flags field of a sigTabT. 1058 const ( 1059 _SigNotify = 1 << iota // let signal.Notify have signal, even if from kernel 1060 _SigKill // if signal.Notify doesn't take it, exit quietly 1061 _SigThrow // if signal.Notify doesn't take it, exit loudly 1062 _SigPanic // if the signal is from the kernel, panic 1063 _SigDefault // if the signal isn't explicitly requested, don't monitor it 1064 _SigGoExit // cause all runtime procs to exit (only used on Plan 9). 1065 _SigSetStack // Don't explicitly install handler, but add SA_ONSTACK to existing libc handler 1066 _SigUnblock // always unblock; see blockableSig 1067 _SigIgn // _SIG_DFL action is to ignore the signal 1068 ) 1069 1070 // Layout of in-memory per-function information prepared by linker 1071 // See https://golang.org/s/go12symtab. 1072 // Keep in sync with linker (../cmd/link/internal/ld/pcln.go:/pclntab) 1073 // and with package debug/gosym and with symtab.go in package runtime. 1074 type _func struct { 1075 sys.NotInHeap // Only in static data 1076 1077 entryOff uint32 // start pc, as offset from moduledata.text 1078 nameOff int32 // function name, as index into moduledata.funcnametab. 1079 1080 args int32 // in/out args size 1081 deferreturn uint32 // offset of start of a deferreturn call instruction from entry, if any. 1082 1083 pcsp uint32 1084 pcfile uint32 1085 pcln uint32 1086 npcdata uint32 1087 cuOffset uint32 // runtime.cutab offset of this function's CU 1088 startLine int32 // line number of start of function (func keyword/TEXT directive) 1089 funcID abi.FuncID // set for certain special runtime functions 1090 flag abi.FuncFlag 1091 _ [1]byte // pad 1092 nfuncdata uint8 // must be last, must end on a uint32-aligned boundary 1093 1094 // The end of the struct is followed immediately by two variable-length 1095 // arrays that reference the pcdata and funcdata locations for this 1096 // function. 1097 1098 // pcdata contains the offset into moduledata.pctab for the start of 1099 // that index's table. e.g., 1100 // &moduledata.pctab[_func.pcdata[_PCDATA_UnsafePoint]] is the start of 1101 // the unsafe point table. 1102 // 1103 // An offset of 0 indicates that there is no table. 1104 // 1105 // pcdata [npcdata]uint32 1106 1107 // funcdata contains the offset past moduledata.gofunc which contains a 1108 // pointer to that index's funcdata. e.g., 1109 // *(moduledata.gofunc + _func.funcdata[_FUNCDATA_ArgsPointerMaps]) is 1110 // the argument pointer map. 1111 // 1112 // An offset of ^uint32(0) indicates that there is no entry. 1113 // 1114 // funcdata [nfuncdata]uint32 1115 } 1116 1117 // Pseudo-Func that is returned for PCs that occur in inlined code. 1118 // A *Func can be either a *_func or a *funcinl, and they are distinguished 1119 // by the first uintptr. 1120 // 1121 // TODO(austin): Can we merge this with inlinedCall? 1122 type funcinl struct { 1123 ones uint32 // set to ^0 to distinguish from _func 1124 entry uintptr // entry of the real (the "outermost") frame 1125 name string 1126 file string 1127 line int32 1128 startLine int32 1129 } 1130 1131 type itab = abi.ITab 1132 1133 // Lock-free stack node. 1134 // Also known to export_test.go. 1135 type lfnode struct { 1136 next uint64 1137 pushcnt uintptr 1138 } 1139 1140 type forcegcstate struct { 1141 lock mutex 1142 g *g 1143 idle atomic.Bool 1144 } 1145 1146 // A _defer holds an entry on the list of deferred calls. 1147 // If you add a field here, add code to clear it in deferProcStack. 1148 // This struct must match the code in cmd/compile/internal/ssagen/ssa.go:deferstruct 1149 // and cmd/compile/internal/ssagen/ssa.go:(*state).call. 1150 // Some defers will be allocated on the stack and some on the heap. 1151 // All defers are logically part of the stack, so write barriers to 1152 // initialize them are not required. All defers must be manually scanned, 1153 // and for heap defers, marked. 1154 type _defer struct { 1155 heap bool 1156 rangefunc bool // true for rangefunc list 1157 sp uintptr // sp at time of defer 1158 pc uintptr // pc at time of defer 1159 fn func() // can be nil for open-coded defers 1160 link *_defer // next defer on G; can point to either heap or stack! 1161 1162 // If rangefunc is true, *head is the head of the atomic linked list 1163 // during a range-over-func execution. 1164 head *atomic.Pointer[_defer] 1165 } 1166 1167 // A _panic holds information about an active panic. 1168 // 1169 // A _panic value must only ever live on the stack. 1170 // 1171 // The gopanicFP and link fields are stack pointers, but don't need special 1172 // handling during stack growth: because they are pointer-typed and 1173 // _panic values only live on the stack, regular stack pointer 1174 // adjustment takes care of them. 1175 type _panic struct { 1176 arg any // argument to panic 1177 link *_panic // link to earlier panic 1178 1179 // startPC and startSP track where _panic.start was called. 1180 // (These are the SP and PC of the gopanic frame itself.) 1181 startPC uintptr 1182 startSP unsafe.Pointer 1183 1184 // The current stack frame that we're running deferred calls for. 1185 pc uintptr 1186 sp unsafe.Pointer 1187 fp unsafe.Pointer 1188 1189 // retpc stores the PC where the panic should jump back to, if the 1190 // function last returned by _panic.nextDefer() recovers the panic. 1191 retpc uintptr 1192 1193 // Extra state for handling open-coded defers. 1194 deferBitsPtr *uint8 1195 slotsPtr unsafe.Pointer 1196 1197 recovered bool // whether this panic has been recovered 1198 repanicked bool // whether this panic repanicked 1199 goexit bool 1200 deferreturn bool 1201 1202 gopanicFP unsafe.Pointer // frame pointer of the gopanic frame 1203 } 1204 1205 // savedOpenDeferState tracks the extra state from _panic that's 1206 // necessary for deferreturn to pick up where gopanic left off, 1207 // without needing to unwind the stack. 1208 type savedOpenDeferState struct { 1209 retpc uintptr 1210 deferBitsOffset uintptr 1211 slotsOffset uintptr 1212 } 1213 1214 // ancestorInfo records details of where a goroutine was started. 1215 type ancestorInfo struct { 1216 pcs []uintptr // pcs from the stack of this goroutine 1217 goid uint64 // goroutine id of this goroutine; original goroutine possibly dead 1218 gopc uintptr // pc of go statement that created this goroutine 1219 } 1220 1221 // A waitReason explains why a goroutine has been stopped. 1222 // See gopark. Do not re-use waitReasons, add new ones. 1223 type waitReason uint8 1224 1225 const ( 1226 waitReasonZero waitReason = iota // "" 1227 waitReasonGCAssistMarking // "GC assist marking" 1228 waitReasonIOWait // "IO wait" 1229 waitReasonDumpingHeap // "dumping heap" 1230 waitReasonGarbageCollection // "garbage collection" 1231 waitReasonGarbageCollectionScan // "garbage collection scan" 1232 waitReasonPanicWait // "panicwait" 1233 waitReasonGCAssistWait // "GC assist wait" 1234 waitReasonGCSweepWait // "GC sweep wait" 1235 waitReasonGCScavengeWait // "GC scavenge wait" 1236 waitReasonFinalizerWait // "finalizer wait" 1237 waitReasonForceGCIdle // "force gc (idle)" 1238 waitReasonUpdateGOMAXPROCSIdle // "GOMAXPROCS updater (idle)" 1239 waitReasonSemacquire // "semacquire" 1240 waitReasonSleep // "sleep" 1241 waitReasonChanReceiveNilChan // "chan receive (nil chan)" 1242 waitReasonChanSendNilChan // "chan send (nil chan)" 1243 waitReasonSelectNoCases // "select (no cases)" 1244 waitReasonSelect // "select" 1245 waitReasonChanReceive // "chan receive" 1246 waitReasonChanSend // "chan send" 1247 waitReasonSyncCondWait // "sync.Cond.Wait" 1248 waitReasonSyncMutexLock // "sync.Mutex.Lock" 1249 waitReasonSyncRWMutexRLock // "sync.RWMutex.RLock" 1250 waitReasonSyncRWMutexLock // "sync.RWMutex.Lock" 1251 waitReasonSyncWaitGroupWait // "sync.WaitGroup.Wait" 1252 waitReasonTraceReaderBlocked // "trace reader (blocked)" 1253 waitReasonWaitForGCCycle // "wait for GC cycle" 1254 waitReasonGCWorkerIdle // "GC worker (idle)" 1255 waitReasonGCWorkerActive // "GC worker (active)" 1256 waitReasonPreempted // "preempted" 1257 waitReasonDebugCall // "debug call" 1258 waitReasonGCMarkTermination // "GC mark termination" 1259 waitReasonStoppingTheWorld // "stopping the world" 1260 waitReasonFlushProcCaches // "flushing proc caches" 1261 waitReasonTraceGoroutineStatus // "trace goroutine status" 1262 waitReasonTraceProcStatus // "trace proc status" 1263 waitReasonPageTraceFlush // "page trace flush" 1264 waitReasonCoroutine // "coroutine" 1265 waitReasonGCWeakToStrongWait // "GC weak to strong wait" 1266 waitReasonSynctestRun // "synctest.Run" 1267 waitReasonSynctestWait // "synctest.Wait" 1268 waitReasonSynctestChanReceive // "chan receive (durable)" 1269 waitReasonSynctestChanSend // "chan send (durable)" 1270 waitReasonSynctestSelect // "select (durable)" 1271 waitReasonSynctestWaitGroupWait // "sync.WaitGroup.Wait (durable)" 1272 waitReasonCleanupWait // "cleanup wait" 1273 ) 1274 1275 var waitReasonStrings = [...]string{ 1276 waitReasonZero: "", 1277 waitReasonGCAssistMarking: "GC assist marking", 1278 waitReasonIOWait: "IO wait", 1279 waitReasonChanReceiveNilChan: "chan receive (nil chan)", 1280 waitReasonChanSendNilChan: "chan send (nil chan)", 1281 waitReasonDumpingHeap: "dumping heap", 1282 waitReasonGarbageCollection: "garbage collection", 1283 waitReasonGarbageCollectionScan: "garbage collection scan", 1284 waitReasonPanicWait: "panicwait", 1285 waitReasonSelect: "select", 1286 waitReasonSelectNoCases: "select (no cases)", 1287 waitReasonGCAssistWait: "GC assist wait", 1288 waitReasonGCSweepWait: "GC sweep wait", 1289 waitReasonGCScavengeWait: "GC scavenge wait", 1290 waitReasonChanReceive: "chan receive", 1291 waitReasonChanSend: "chan send", 1292 waitReasonFinalizerWait: "finalizer wait", 1293 waitReasonForceGCIdle: "force gc (idle)", 1294 waitReasonUpdateGOMAXPROCSIdle: "GOMAXPROCS updater (idle)", 1295 waitReasonSemacquire: "semacquire", 1296 waitReasonSleep: "sleep", 1297 waitReasonSyncCondWait: "sync.Cond.Wait", 1298 waitReasonSyncMutexLock: "sync.Mutex.Lock", 1299 waitReasonSyncRWMutexRLock: "sync.RWMutex.RLock", 1300 waitReasonSyncRWMutexLock: "sync.RWMutex.Lock", 1301 waitReasonSyncWaitGroupWait: "sync.WaitGroup.Wait", 1302 waitReasonTraceReaderBlocked: "trace reader (blocked)", 1303 waitReasonWaitForGCCycle: "wait for GC cycle", 1304 waitReasonGCWorkerIdle: "GC worker (idle)", 1305 waitReasonGCWorkerActive: "GC worker (active)", 1306 waitReasonPreempted: "preempted", 1307 waitReasonDebugCall: "debug call", 1308 waitReasonGCMarkTermination: "GC mark termination", 1309 waitReasonStoppingTheWorld: "stopping the world", 1310 waitReasonFlushProcCaches: "flushing proc caches", 1311 waitReasonTraceGoroutineStatus: "trace goroutine status", 1312 waitReasonTraceProcStatus: "trace proc status", 1313 waitReasonPageTraceFlush: "page trace flush", 1314 waitReasonCoroutine: "coroutine", 1315 waitReasonGCWeakToStrongWait: "GC weak to strong wait", 1316 waitReasonSynctestRun: "synctest.Run", 1317 waitReasonSynctestWait: "synctest.Wait", 1318 waitReasonSynctestChanReceive: "chan receive (durable)", 1319 waitReasonSynctestChanSend: "chan send (durable)", 1320 waitReasonSynctestSelect: "select (durable)", 1321 waitReasonSynctestWaitGroupWait: "sync.WaitGroup.Wait (durable)", 1322 waitReasonCleanupWait: "cleanup wait", 1323 } 1324 1325 func (w waitReason) String() string { 1326 if w < 0 || w >= waitReason(len(waitReasonStrings)) { 1327 return "unknown wait reason" 1328 } 1329 return waitReasonStrings[w] 1330 } 1331 1332 // isMutexWait returns true if the goroutine is blocked because of 1333 // sync.Mutex.Lock or sync.RWMutex.[R]Lock. 1334 // 1335 //go:nosplit 1336 func (w waitReason) isMutexWait() bool { 1337 return w == waitReasonSyncMutexLock || 1338 w == waitReasonSyncRWMutexRLock || 1339 w == waitReasonSyncRWMutexLock 1340 } 1341 1342 // isSyncWait returns true if the goroutine is blocked because of 1343 // sync library primitive operations. 1344 // 1345 //go:nosplit 1346 func (w waitReason) isSyncWait() bool { 1347 return waitReasonSyncCondWait <= w && w <= waitReasonSyncWaitGroupWait 1348 } 1349 1350 // isChanWait is true if the goroutine is blocked because of non-nil 1351 // channel operations or a select statement with at least one case. 1352 // 1353 //go:nosplit 1354 func (w waitReason) isChanWait() bool { 1355 return w == waitReasonSelect || 1356 w == waitReasonChanReceive || 1357 w == waitReasonChanSend 1358 } 1359 1360 func (w waitReason) isWaitingForSuspendG() bool { 1361 return isWaitingForSuspendG[w] 1362 } 1363 1364 // isWaitingForSuspendG indicates that a goroutine is only entering _Gwaiting and 1365 // setting a waitReason because it needs to be able to let the suspendG 1366 // (used by the GC and the execution tracer) take ownership of its stack. 1367 // The G is always actually executing on the system stack in these cases. 1368 // 1369 // TODO(mknyszek): Consider replacing this with a new dedicated G status. 1370 var isWaitingForSuspendG = [len(waitReasonStrings)]bool{ 1371 waitReasonStoppingTheWorld: true, 1372 waitReasonGCMarkTermination: true, 1373 waitReasonGarbageCollection: true, 1374 waitReasonGarbageCollectionScan: true, 1375 waitReasonTraceGoroutineStatus: true, 1376 waitReasonTraceProcStatus: true, 1377 waitReasonPageTraceFlush: true, 1378 waitReasonGCAssistMarking: true, 1379 waitReasonGCWorkerActive: true, 1380 waitReasonFlushProcCaches: true, 1381 } 1382 1383 func (w waitReason) isIdleInSynctest() bool { 1384 return isIdleInSynctest[w] 1385 } 1386 1387 // isIdleInSynctest indicates that a goroutine is considered idle by synctest.Wait. 1388 var isIdleInSynctest = [len(waitReasonStrings)]bool{ 1389 waitReasonChanReceiveNilChan: true, 1390 waitReasonChanSendNilChan: true, 1391 waitReasonSelectNoCases: true, 1392 waitReasonSleep: true, 1393 waitReasonSyncCondWait: true, 1394 waitReasonSynctestWaitGroupWait: true, 1395 waitReasonCoroutine: true, 1396 waitReasonSynctestRun: true, 1397 waitReasonSynctestWait: true, 1398 waitReasonSynctestChanReceive: true, 1399 waitReasonSynctestChanSend: true, 1400 waitReasonSynctestSelect: true, 1401 } 1402 1403 var ( 1404 // Linked-list of all Ms. Written under sched.lock, read atomically. 1405 allm *m 1406 1407 gomaxprocs int32 1408 numCPUStartup int32 1409 forcegc forcegcstate 1410 sched schedt 1411 newprocs int32 1412 ) 1413 1414 var ( 1415 // allpLock protects P-less reads and size changes of allp, idlepMask, 1416 // and timerpMask, and all writes to allp. 1417 allpLock mutex 1418 1419 // len(allp) == gomaxprocs; may change at safe points, otherwise 1420 // immutable. 1421 allp []*p 1422 1423 // Bitmask of Ps in _Pidle list, one bit per P. Reads and writes must 1424 // be atomic. Length may change at safe points. 1425 // 1426 // Each P must update only its own bit. In order to maintain 1427 // consistency, a P going idle must set the idle mask simultaneously with 1428 // updates to the idle P list under the sched.lock, otherwise a racing 1429 // pidleget may clear the mask before pidleput sets the mask, 1430 // corrupting the bitmap. 1431 // 1432 // N.B., procresize takes ownership of all Ps in stopTheWorldWithSema. 1433 idlepMask pMask 1434 1435 // Bitmask of Ps that may have a timer, one bit per P. Reads and writes 1436 // must be atomic. Length may change at safe points. 1437 // 1438 // Ideally, the timer mask would be kept immediately consistent on any timer 1439 // operations. Unfortunately, updating a shared global data structure in the 1440 // timer hot path adds too much overhead in applications frequently switching 1441 // between no timers and some timers. 1442 // 1443 // As a compromise, the timer mask is updated only on pidleget / pidleput. A 1444 // running P (returned by pidleget) may add a timer at any time, so its mask 1445 // must be set. An idle P (passed to pidleput) cannot add new timers while 1446 // idle, so if it has no timers at that time, its mask may be cleared. 1447 // 1448 // Thus, we get the following effects on timer-stealing in findRunnable: 1449 // 1450 // - Idle Ps with no timers when they go idle are never checked in findRunnable 1451 // (for work- or timer-stealing; this is the ideal case). 1452 // - Running Ps must always be checked. 1453 // - Idle Ps whose timers are stolen must continue to be checked until they run 1454 // again, even after timer expiration. 1455 // 1456 // When the P starts running again, the mask should be set, as a timer may be 1457 // added at any time. 1458 // 1459 // TODO(prattmic): Additional targeted updates may improve the above cases. 1460 // e.g., updating the mask when stealing a timer. 1461 timerpMask pMask 1462 ) 1463 1464 // goarmsoftfp is used by runtime/cgo assembly. 1465 // 1466 //go:linkname goarmsoftfp 1467 1468 var ( 1469 // Pool of GC parked background workers. Entries are type 1470 // *gcBgMarkWorkerNode. 1471 gcBgMarkWorkerPool lfstack 1472 1473 // Total number of gcBgMarkWorker goroutines. Protected by worldsema. 1474 gcBgMarkWorkerCount int32 1475 1476 // Information about what cpu features are available. 1477 // Packages outside the runtime should not use these 1478 // as they are not an external api. 1479 // Set on startup in asm_{386,amd64}.s 1480 processorVersionInfo uint32 1481 isIntel bool 1482 ) 1483 1484 // set by cmd/link on arm systems 1485 // accessed using linkname by internal/runtime/atomic. 1486 // 1487 // goarm should be an internal detail, 1488 // but widely used packages access it using linkname. 1489 // Notable members of the hall of shame include: 1490 // - github.com/creativeprojects/go-selfupdate 1491 // 1492 // Do not remove or change the type signature. 1493 // See go.dev/issue/67401. 1494 // 1495 //go:linkname goarm 1496 var ( 1497 goarm uint8 1498 goarmsoftfp uint8 1499 ) 1500 1501 // Set by the linker so the runtime can determine the buildmode. 1502 var ( 1503 islibrary bool // -buildmode=c-shared 1504 isarchive bool // -buildmode=c-archive 1505 ) 1506 1507 // Must agree with internal/buildcfg.FramePointerEnabled. 1508 const framepointer_enabled = GOARCH == "amd64" || GOARCH == "arm64" 1509 1510 // getcallerfp returns the frame pointer of the caller of the caller 1511 // of this function. 1512 // 1513 //go:nosplit 1514 //go:noinline 1515 func getcallerfp() uintptr { 1516 fp := getfp() // This frame's FP. 1517 if fp != 0 { 1518 fp = *(*uintptr)(unsafe.Pointer(fp)) // The caller's FP. 1519 fp = *(*uintptr)(unsafe.Pointer(fp)) // The caller's caller's FP. 1520 } 1521 return fp 1522 } 1523