github.com/sanprasirt/go@v0.0.0-20170607001320-a027466e4b6d/src/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 "runtime/internal/atomic" 9 "runtime/internal/sys" 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 // _Gidle means this goroutine was just allocated and has not 26 // yet been initialized. 27 _Gidle = iota // 0 28 29 // _Grunnable means this goroutine is on a run queue. It is 30 // not currently executing user code. The stack is not owned. 31 _Grunnable // 1 32 33 // _Grunning means this goroutine may execute user code. The 34 // stack is owned by this goroutine. It is not on a run queue. 35 // It is assigned an M and a P. 36 _Grunning // 2 37 38 // _Gsyscall means this goroutine is executing a system call. 39 // It is not executing user code. The stack is owned by this 40 // goroutine. It is not on a run queue. It is assigned an M. 41 _Gsyscall // 3 42 43 // _Gwaiting means this goroutine is blocked in the runtime. 44 // It is not executing user code. It is not on a run queue, 45 // but should be recorded somewhere (e.g., a channel wait 46 // queue) so it can be ready()d when necessary. The stack is 47 // not owned *except* that a channel operation may read or 48 // write parts of the stack under the appropriate channel 49 // lock. Otherwise, it is not safe to access the stack after a 50 // goroutine enters _Gwaiting (e.g., it may get moved). 51 _Gwaiting // 4 52 53 // _Gmoribund_unused is currently unused, but hardcoded in gdb 54 // scripts. 55 _Gmoribund_unused // 5 56 57 // _Gdead means this goroutine is currently unused. It may be 58 // just exited, on a free list, or just being initialized. It 59 // is not executing user code. It may or may not have a stack 60 // allocated. The G and its stack (if any) are owned by the M 61 // that is exiting the G or that obtained the G from the free 62 // list. 63 _Gdead // 6 64 65 // _Genqueue_unused is currently unused. 66 _Genqueue_unused // 7 67 68 // _Gcopystack means this goroutine's stack is being moved. It 69 // is not executing user code and is not on a run queue. The 70 // stack is owned by the goroutine that put it in _Gcopystack. 71 _Gcopystack // 8 72 73 // _Gscan combined with one of the above states other than 74 // _Grunning indicates that GC is scanning the stack. The 75 // goroutine is not executing user code and the stack is owned 76 // by the goroutine that set the _Gscan bit. 77 // 78 // _Gscanrunning is different: it is used to briefly block 79 // state transitions while GC signals the G to scan its own 80 // stack. This is otherwise like _Grunning. 81 // 82 // atomicstatus&~Gscan gives the state the goroutine will 83 // return to when the scan completes. 84 _Gscan = 0x1000 85 _Gscanrunnable = _Gscan + _Grunnable // 0x1001 86 _Gscanrunning = _Gscan + _Grunning // 0x1002 87 _Gscansyscall = _Gscan + _Gsyscall // 0x1003 88 _Gscanwaiting = _Gscan + _Gwaiting // 0x1004 89 ) 90 91 const ( 92 // P status 93 _Pidle = iota 94 _Prunning // Only this P is allowed to change from _Prunning. 95 _Psyscall 96 _Pgcstop 97 _Pdead 98 ) 99 100 // Mutual exclusion locks. In the uncontended case, 101 // as fast as spin locks (just a few user-level instructions), 102 // but on the contention path they sleep in the kernel. 103 // A zeroed Mutex is unlocked (no need to initialize each lock). 104 type mutex struct { 105 // Futex-based impl treats it as uint32 key, 106 // while sema-based impl as M* waitm. 107 // Used to be a union, but unions break precise GC. 108 key uintptr 109 } 110 111 // sleep and wakeup on one-time events. 112 // before any calls to notesleep or notewakeup, 113 // must call noteclear to initialize the Note. 114 // then, exactly one thread can call notesleep 115 // and exactly one thread can call notewakeup (once). 116 // once notewakeup has been called, the notesleep 117 // will return. future notesleep will return immediately. 118 // subsequent noteclear must be called only after 119 // previous notesleep has returned, e.g. it's disallowed 120 // to call noteclear straight after notewakeup. 121 // 122 // notetsleep is like notesleep but wakes up after 123 // a given number of nanoseconds even if the event 124 // has not yet happened. if a goroutine uses notetsleep to 125 // wake up early, it must wait to call noteclear until it 126 // can be sure that no other goroutine is calling 127 // notewakeup. 128 // 129 // notesleep/notetsleep are generally called on g0, 130 // notetsleepg is similar to notetsleep but is called on user g. 131 type note struct { 132 // Futex-based impl treats it as uint32 key, 133 // while sema-based impl as M* waitm. 134 // Used to be a union, but unions break precise GC. 135 key uintptr 136 } 137 138 type funcval struct { 139 fn uintptr 140 // variable-size, fn-specific data here 141 } 142 143 type iface struct { 144 tab *itab 145 data unsafe.Pointer 146 } 147 148 type eface struct { 149 _type *_type 150 data unsafe.Pointer 151 } 152 153 func efaceOf(ep *interface{}) *eface { 154 return (*eface)(unsafe.Pointer(ep)) 155 } 156 157 // The guintptr, muintptr, and puintptr are all used to bypass write barriers. 158 // It is particularly important to avoid write barriers when the current P has 159 // been released, because the GC thinks the world is stopped, and an 160 // unexpected write barrier would not be synchronized with the GC, 161 // which can lead to a half-executed write barrier that has marked the object 162 // but not queued it. If the GC skips the object and completes before the 163 // queuing can occur, it will incorrectly free the object. 164 // 165 // We tried using special assignment functions invoked only when not 166 // holding a running P, but then some updates to a particular memory 167 // word went through write barriers and some did not. This breaks the 168 // write barrier shadow checking mode, and it is also scary: better to have 169 // a word that is completely ignored by the GC than to have one for which 170 // only a few updates are ignored. 171 // 172 // Gs, Ms, and Ps are always reachable via true pointers in the 173 // allgs, allm, and allp lists or (during allocation before they reach those lists) 174 // from stack variables. 175 176 // A guintptr holds a goroutine pointer, but typed as a uintptr 177 // to bypass write barriers. It is used in the Gobuf goroutine state 178 // and in scheduling lists that are manipulated without a P. 179 // 180 // The Gobuf.g goroutine pointer is almost always updated by assembly code. 181 // In one of the few places it is updated by Go code - func save - it must be 182 // treated as a uintptr to avoid a write barrier being emitted at a bad time. 183 // Instead of figuring out how to emit the write barriers missing in the 184 // assembly manipulation, we change the type of the field to uintptr, 185 // so that it does not require write barriers at all. 186 // 187 // Goroutine structs are published in the allg list and never freed. 188 // That will keep the goroutine structs from being collected. 189 // There is never a time that Gobuf.g's contain the only references 190 // to a goroutine: the publishing of the goroutine in allg comes first. 191 // Goroutine pointers are also kept in non-GC-visible places like TLS, 192 // so I can't see them ever moving. If we did want to start moving data 193 // in the GC, we'd need to allocate the goroutine structs from an 194 // alternate arena. Using guintptr doesn't make that problem any worse. 195 type guintptr uintptr 196 197 //go:nosplit 198 func (gp guintptr) ptr() *g { return (*g)(unsafe.Pointer(gp)) } 199 200 //go:nosplit 201 func (gp *guintptr) set(g *g) { *gp = guintptr(unsafe.Pointer(g)) } 202 203 //go:nosplit 204 func (gp *guintptr) cas(old, new guintptr) bool { 205 return atomic.Casuintptr((*uintptr)(unsafe.Pointer(gp)), uintptr(old), uintptr(new)) 206 } 207 208 // setGNoWB performs *gp = new without a write barrier. 209 // For times when it's impractical to use a guintptr. 210 //go:nosplit 211 //go:nowritebarrier 212 func setGNoWB(gp **g, new *g) { 213 (*guintptr)(unsafe.Pointer(gp)).set(new) 214 } 215 216 type puintptr uintptr 217 218 //go:nosplit 219 func (pp puintptr) ptr() *p { return (*p)(unsafe.Pointer(pp)) } 220 221 //go:nosplit 222 func (pp *puintptr) set(p *p) { *pp = puintptr(unsafe.Pointer(p)) } 223 224 type muintptr uintptr 225 226 //go:nosplit 227 func (mp muintptr) ptr() *m { return (*m)(unsafe.Pointer(mp)) } 228 229 //go:nosplit 230 func (mp *muintptr) set(m *m) { *mp = muintptr(unsafe.Pointer(m)) } 231 232 // setMNoWB performs *mp = new without a write barrier. 233 // For times when it's impractical to use an muintptr. 234 //go:nosplit 235 //go:nowritebarrier 236 func setMNoWB(mp **m, new *m) { 237 (*muintptr)(unsafe.Pointer(mp)).set(new) 238 } 239 240 type gobuf struct { 241 // The offsets of sp, pc, and g are known to (hard-coded in) libmach. 242 // 243 // ctxt is unusual with respect to GC: it may be a 244 // heap-allocated funcval so write require a write barrier, 245 // but gobuf needs to be cleared from assembly. We take 246 // advantage of the fact that the only path that uses a 247 // non-nil ctxt is morestack. As a result, gogo is the only 248 // place where it may not already be nil, so gogo uses an 249 // explicit write barrier. Everywhere else that resets the 250 // gobuf asserts that ctxt is already nil. 251 sp uintptr 252 pc uintptr 253 g guintptr 254 ctxt unsafe.Pointer // this has to be a pointer so that gc scans it 255 ret sys.Uintreg 256 lr uintptr 257 bp uintptr // for GOEXPERIMENT=framepointer 258 } 259 260 // sudog represents a g in a wait list, such as for sending/receiving 261 // on a channel. 262 // 263 // sudog is necessary because the g ↔ synchronization object relation 264 // is many-to-many. A g can be on many wait lists, so there may be 265 // many sudogs for one g; and many gs may be waiting on the same 266 // synchronization object, so there may be many sudogs for one object. 267 // 268 // sudogs are allocated from a special pool. Use acquireSudog and 269 // releaseSudog to allocate and free them. 270 type sudog struct { 271 // The following fields are protected by the hchan.lock of the 272 // channel this sudog is blocking on. shrinkstack depends on 273 // this for sudogs involved in channel ops. 274 275 g *g 276 selectdone *uint32 // CAS to 1 to win select race (may point to stack) 277 next *sudog 278 prev *sudog 279 elem unsafe.Pointer // data element (may point to stack) 280 281 // The following fields are never accessed concurrently. 282 // For channels, waitlink is only accessed by g. 283 // For semaphores, all fields (including the ones above) 284 // are only accessed when holding a semaRoot lock. 285 286 acquiretime int64 287 releasetime int64 288 ticket uint32 289 parent *sudog // semaRoot binary tree 290 waitlink *sudog // g.waiting list or semaRoot 291 waittail *sudog // semaRoot 292 c *hchan // channel 293 } 294 295 type libcall struct { 296 fn uintptr 297 n uintptr // number of parameters 298 args uintptr // parameters 299 r1 uintptr // return values 300 r2 uintptr 301 err uintptr // error number 302 } 303 304 // describes how to handle callback 305 type wincallbackcontext struct { 306 gobody unsafe.Pointer // go function to call 307 argsize uintptr // callback arguments size (in bytes) 308 restorestack uintptr // adjust stack on return by (in bytes) (386 only) 309 cleanstack bool 310 } 311 312 // Stack describes a Go execution stack. 313 // The bounds of the stack are exactly [lo, hi), 314 // with no implicit data structures on either side. 315 type stack struct { 316 lo uintptr 317 hi uintptr 318 } 319 320 type g struct { 321 // Stack parameters. 322 // stack describes the actual stack memory: [stack.lo, stack.hi). 323 // stackguard0 is the stack pointer compared in the Go stack growth prologue. 324 // It is stack.lo+StackGuard normally, but can be StackPreempt to trigger a preemption. 325 // stackguard1 is the stack pointer compared in the C stack growth prologue. 326 // It is stack.lo+StackGuard on g0 and gsignal stacks. 327 // It is ~0 on other goroutine stacks, to trigger a call to morestackc (and crash). 328 stack stack // offset known to runtime/cgo 329 stackguard0 uintptr // offset known to liblink 330 stackguard1 uintptr // offset known to liblink 331 332 _panic *_panic // innermost panic - offset known to liblink 333 _defer *_defer // innermost defer 334 m *m // current m; offset known to arm liblink 335 sched gobuf 336 syscallsp uintptr // if status==Gsyscall, syscallsp = sched.sp to use during gc 337 syscallpc uintptr // if status==Gsyscall, syscallpc = sched.pc to use during gc 338 stktopsp uintptr // expected sp at top of stack, to check in traceback 339 param unsafe.Pointer // passed parameter on wakeup 340 atomicstatus uint32 341 stackLock uint32 // sigprof/scang lock; TODO: fold in to atomicstatus 342 goid int64 343 waitsince int64 // approx time when the g become blocked 344 waitreason string // if status==Gwaiting 345 schedlink guintptr 346 preempt bool // preemption signal, duplicates stackguard0 = stackpreempt 347 paniconfault bool // panic (instead of crash) on unexpected fault address 348 preemptscan bool // preempted g does scan for gc 349 gcscandone bool // g has scanned stack; protected by _Gscan bit in status 350 gcscanvalid bool // false at start of gc cycle, true if G has not run since last scan; TODO: remove? 351 throwsplit bool // must not split stack 352 raceignore int8 // ignore race detection events 353 sysblocktraced bool // StartTrace has emitted EvGoInSyscall about this goroutine 354 sysexitticks int64 // cputicks when syscall has returned (for tracing) 355 traceseq uint64 // trace event sequencer 356 tracelastp puintptr // last P emitted an event for this goroutine 357 lockedm *m 358 sig uint32 359 writebuf []byte 360 sigcode0 uintptr 361 sigcode1 uintptr 362 sigpc uintptr 363 gopc uintptr // pc of go statement that created this goroutine 364 startpc uintptr // pc of goroutine function 365 racectx uintptr 366 waiting *sudog // sudog structures this g is waiting on (that have a valid elem ptr); in lock order 367 cgoCtxt []uintptr // cgo traceback context 368 labels unsafe.Pointer // profiler labels 369 timer *timer // cached timer for time.Sleep 370 371 // Per-G GC state 372 373 // gcAssistBytes is this G's GC assist credit in terms of 374 // bytes allocated. If this is positive, then the G has credit 375 // to allocate gcAssistBytes bytes without assisting. If this 376 // is negative, then the G must correct this by performing 377 // scan work. We track this in bytes to make it fast to update 378 // and check for debt in the malloc hot path. The assist ratio 379 // determines how this corresponds to scan work debt. 380 gcAssistBytes int64 381 } 382 383 type m struct { 384 g0 *g // goroutine with scheduling stack 385 morebuf gobuf // gobuf arg to morestack 386 divmod uint32 // div/mod denominator for arm - known to liblink 387 388 // Fields not known to debuggers. 389 procid uint64 // for debuggers, but offset not hard-coded 390 gsignal *g // signal-handling g 391 sigmask sigset // storage for saved signal mask 392 tls [6]uintptr // thread-local storage (for x86 extern register) 393 mstartfn func() 394 curg *g // current running goroutine 395 caughtsig guintptr // goroutine running during fatal signal 396 p puintptr // attached p for executing go code (nil if not executing go code) 397 nextp puintptr 398 id int32 399 mallocing int32 400 throwing int32 401 preemptoff string // if != "", keep curg running on this m 402 locks int32 403 softfloat int32 404 dying int32 405 profilehz int32 406 helpgc int32 407 spinning bool // m is out of work and is actively looking for work 408 blocked bool // m is blocked on a note 409 inwb bool // m is executing a write barrier 410 newSigstack bool // minit on C thread called sigaltstack 411 printlock int8 412 incgo bool // m is executing a cgo call 413 fastrand uint32 414 ncgocall uint64 // number of cgo calls in total 415 ncgo int32 // number of cgo calls currently in progress 416 cgoCallersUse uint32 // if non-zero, cgoCallers in use temporarily 417 cgoCallers *cgoCallers // cgo traceback if crashing in cgo call 418 park note 419 alllink *m // on allm 420 schedlink muintptr 421 mcache *mcache 422 lockedg *g 423 createstack [32]uintptr // stack that created this thread. 424 freglo [16]uint32 // d[i] lsb and f[i] 425 freghi [16]uint32 // d[i] msb and f[i+16] 426 fflag uint32 // floating point compare flags 427 locked uint32 // tracking for lockosthread 428 nextwaitm uintptr // next m waiting for lock 429 needextram bool 430 traceback uint8 431 waitunlockf unsafe.Pointer // todo go func(*g, unsafe.pointer) bool 432 waitlock unsafe.Pointer 433 waittraceev byte 434 waittraceskip int 435 startingtrace bool 436 syscalltick uint32 437 thread uintptr // thread handle 438 439 // these are here because they are too large to be on the stack 440 // of low-level NOSPLIT functions. 441 libcall libcall 442 libcallpc uintptr // for cpu profiler 443 libcallsp uintptr 444 libcallg guintptr 445 syscall libcall // stores syscall parameters on windows 446 447 mOS 448 } 449 450 type p struct { 451 lock mutex 452 453 id int32 454 status uint32 // one of pidle/prunning/... 455 link puintptr 456 schedtick uint32 // incremented on every scheduler call 457 syscalltick uint32 // incremented on every system call 458 m muintptr // back-link to associated m (nil if idle) 459 mcache *mcache 460 racectx uintptr 461 462 deferpool [5][]*_defer // pool of available defer structs of different sizes (see panic.go) 463 deferpoolbuf [5][32]*_defer 464 465 // Cache of goroutine ids, amortizes accesses to runtime·sched.goidgen. 466 goidcache uint64 467 goidcacheend uint64 468 469 // Queue of runnable goroutines. Accessed without lock. 470 runqhead uint32 471 runqtail uint32 472 runq [256]guintptr 473 // runnext, if non-nil, is a runnable G that was ready'd by 474 // the current G and should be run next instead of what's in 475 // runq if there's time remaining in the running G's time 476 // slice. It will inherit the time left in the current time 477 // slice. If a set of goroutines is locked in a 478 // communicate-and-wait pattern, this schedules that set as a 479 // unit and eliminates the (potentially large) scheduling 480 // latency that otherwise arises from adding the ready'd 481 // goroutines to the end of the run queue. 482 runnext guintptr 483 484 // Available G's (status == Gdead) 485 gfree *g 486 gfreecnt int32 487 488 sudogcache []*sudog 489 sudogbuf [128]*sudog 490 491 tracebuf traceBufPtr 492 493 // traceSweep indicates the sweep events should be traced. 494 // This is used to defer the sweep start event until a span 495 // has actually been swept. 496 traceSweep bool 497 // traceSwept and traceReclaimed track the number of bytes 498 // swept and reclaimed by sweeping in the current sweep loop. 499 traceSwept, traceReclaimed uintptr 500 501 palloc persistentAlloc // per-P to avoid mutex 502 503 // Per-P GC state 504 gcAssistTime int64 // Nanoseconds in assistAlloc 505 gcBgMarkWorker guintptr 506 gcMarkWorkerMode gcMarkWorkerMode 507 508 // gcw is this P's GC work buffer cache. The work buffer is 509 // filled by write barriers, drained by mutator assists, and 510 // disposed on certain GC state transitions. 511 gcw gcWork 512 513 runSafePointFn uint32 // if 1, run sched.safePointFn at next safe point 514 515 pad [sys.CacheLineSize]byte 516 } 517 518 const ( 519 // The max value of GOMAXPROCS. 520 // There are no fundamental restrictions on the value. 521 _MaxGomaxprocs = 1 << 8 522 ) 523 524 type schedt struct { 525 // accessed atomically. keep at top to ensure alignment on 32-bit systems. 526 goidgen uint64 527 lastpoll uint64 528 529 lock mutex 530 531 midle muintptr // idle m's waiting for work 532 nmidle int32 // number of idle m's waiting for work 533 nmidlelocked int32 // number of locked m's waiting for work 534 mcount int32 // number of m's that have been created 535 maxmcount int32 // maximum number of m's allowed (or die) 536 537 ngsys uint32 // number of system goroutines; updated atomically 538 539 pidle puintptr // idle p's 540 npidle uint32 541 nmspinning uint32 // See "Worker thread parking/unparking" comment in proc.go. 542 543 // Global runnable queue. 544 runqhead guintptr 545 runqtail guintptr 546 runqsize int32 547 548 // Global cache of dead G's. 549 gflock mutex 550 gfreeStack *g 551 gfreeNoStack *g 552 ngfree int32 553 554 // Central cache of sudog structs. 555 sudoglock mutex 556 sudogcache *sudog 557 558 // Central pool of available defer structs of different sizes. 559 deferlock mutex 560 deferpool [5]*_defer 561 562 gcwaiting uint32 // gc is waiting to run 563 stopwait int32 564 stopnote note 565 sysmonwait uint32 566 sysmonnote note 567 568 // safepointFn should be called on each P at the next GC 569 // safepoint if p.runSafePointFn is set. 570 safePointFn func(*p) 571 safePointWait int32 572 safePointNote note 573 574 profilehz int32 // cpu profiling rate 575 576 procresizetime int64 // nanotime() of last change to gomaxprocs 577 totaltime int64 // ∫gomaxprocs dt up to procresizetime 578 } 579 580 // The m.locked word holds two pieces of state counting active calls to LockOSThread/lockOSThread. 581 // The low bit (LockExternal) is a boolean reporting whether any LockOSThread call is active. 582 // External locks are not recursive; a second lock is silently ignored. 583 // The upper bits of m.locked record the nesting depth of calls to lockOSThread 584 // (counting up by LockInternal), popped by unlockOSThread (counting down by LockInternal). 585 // Internal locks can be recursive. For instance, a lock for cgo can occur while the main 586 // goroutine is holding the lock during the initialization phase. 587 const ( 588 _LockExternal = 1 589 _LockInternal = 2 590 ) 591 592 const ( 593 _SigNotify = 1 << iota // let signal.Notify have signal, even if from kernel 594 _SigKill // if signal.Notify doesn't take it, exit quietly 595 _SigThrow // if signal.Notify doesn't take it, exit loudly 596 _SigPanic // if the signal is from the kernel, panic 597 _SigDefault // if the signal isn't explicitly requested, don't monitor it 598 _SigGoExit // cause all runtime procs to exit (only used on Plan 9). 599 _SigSetStack // add SA_ONSTACK to libc handler 600 _SigUnblock // unblocked in minit 601 ) 602 603 // Layout of in-memory per-function information prepared by linker 604 // See https://golang.org/s/go12symtab. 605 // Keep in sync with linker (../cmd/link/internal/ld/pcln.go:/pclntab) 606 // and with package debug/gosym and with symtab.go in package runtime. 607 type _func struct { 608 entry uintptr // start pc 609 nameoff int32 // function name 610 611 args int32 // in/out args size 612 _ int32 // previously legacy frame size; kept for layout compatibility 613 614 pcsp int32 615 pcfile int32 616 pcln int32 617 npcdata int32 618 nfuncdata int32 619 } 620 621 // layout of Itab known to compilers 622 // allocated in non-garbage-collected memory 623 // Needs to be in sync with 624 // ../cmd/compile/internal/gc/reflect.go:/^func.dumptypestructs. 625 type itab struct { 626 inter *interfacetype 627 _type *_type 628 link *itab 629 hash uint32 // copy of _type.hash. Used for type switches. 630 bad bool // type does not implement interface 631 inhash bool // has this itab been added to hash? 632 unused [2]byte 633 fun [1]uintptr // variable sized 634 } 635 636 // Lock-free stack node. 637 // // Also known to export_test.go. 638 type lfnode struct { 639 next uint64 640 pushcnt uintptr 641 } 642 643 type forcegcstate struct { 644 lock mutex 645 g *g 646 idle uint32 647 } 648 649 // startup_random_data holds random bytes initialized at startup. These come from 650 // the ELF AT_RANDOM auxiliary vector (vdso_linux_amd64.go or os_linux_386.go). 651 var startupRandomData []byte 652 653 // extendRandom extends the random numbers in r[:n] to the whole slice r. 654 // Treats n<0 as n==0. 655 func extendRandom(r []byte, n int) { 656 if n < 0 { 657 n = 0 658 } 659 for n < len(r) { 660 // Extend random bits using hash function & time seed 661 w := n 662 if w > 16 { 663 w = 16 664 } 665 h := memhash(unsafe.Pointer(&r[n-w]), uintptr(nanotime()), uintptr(w)) 666 for i := 0; i < sys.PtrSize && n < len(r); i++ { 667 r[n] = byte(h) 668 n++ 669 h >>= 8 670 } 671 } 672 } 673 674 // deferred subroutine calls 675 type _defer struct { 676 siz int32 677 started bool 678 sp uintptr // sp at time of defer 679 pc uintptr 680 fn *funcval 681 _panic *_panic // panic that is running defer 682 link *_defer 683 } 684 685 // panics 686 type _panic struct { 687 argp unsafe.Pointer // pointer to arguments of deferred call run during panic; cannot move - known to liblink 688 arg interface{} // argument to panic 689 link *_panic // link to earlier panic 690 recovered bool // whether this panic is over 691 aborted bool // the panic was aborted 692 } 693 694 // stack traces 695 type stkframe struct { 696 fn funcInfo // function being run 697 pc uintptr // program counter within fn 698 continpc uintptr // program counter where execution can continue, or 0 if not 699 lr uintptr // program counter at caller aka link register 700 sp uintptr // stack pointer at pc 701 fp uintptr // stack pointer at caller aka frame pointer 702 varp uintptr // top of local variables 703 argp uintptr // pointer to function arguments 704 arglen uintptr // number of bytes at argp 705 argmap *bitvector // force use of this argmap 706 } 707 708 const ( 709 _TraceRuntimeFrames = 1 << iota // include frames for internal runtime functions. 710 _TraceTrap // the initial PC, SP are from a trap, not a return PC from a call 711 _TraceJumpStack // if traceback is on a systemstack, resume trace at g that called into it 712 ) 713 714 // The maximum number of frames we print for a traceback 715 const _TracebackMaxFrames = 100 716 717 var ( 718 emptystring string 719 allglen uintptr 720 allm *m 721 allp [_MaxGomaxprocs + 1]*p 722 gomaxprocs int32 723 ncpu int32 724 forcegc forcegcstate 725 sched schedt 726 newprocs int32 727 728 // Information about what cpu features are available. 729 // Set on startup in asm_{386,amd64,amd64p32}.s. 730 // Packages outside the runtime should not use these 731 // as they are not an external api. 732 processorVersionInfo uint32 733 isIntel bool 734 lfenceBeforeRdtsc bool 735 support_aes bool 736 support_avx bool 737 support_avx2 bool 738 support_bmi1 bool 739 support_bmi2 bool 740 support_erms bool 741 support_osxsave bool 742 support_popcnt bool 743 support_sse2 bool 744 support_sse41 bool 745 support_sse42 bool 746 support_ssse3 bool 747 748 goarm uint8 // set by cmd/link on arm systems 749 framepointer_enabled bool // set by cmd/link 750 ) 751 752 // Set by the linker so the runtime can determine the buildmode. 753 var ( 754 islibrary bool // -buildmode=c-shared 755 isarchive bool // -buildmode=c-archive 756 )