go version go1.12.5 darwin/amd64
14章Go启动疏导
// The bootstrap sequence is://// call osinit// call schedinit// make & queue new G// call runtime·mstart//// The new G calls runtime·main.
TEXT runtime·rt0_go(SB),NOSPLIT,$0---略---CALL runtime·args(SB)CALL runtime·osinit(SB)CALL runtime·schedinit(SB)// create a new goroutine to start programMOVQ $runtime·mainPC(SB), AX // entry (runtime·mainPC+0(SB)/8,$runtime·main(SB))PUSHQ AXPUSHQ $0 // arg sizeCALL runtime·newproc(SB)POPQ AXPOPQ AX// start this MCALL runtime·mstart(SB)CALL runtime·abort(SB) // mstart should never returnRET
osinit
func osinit() { // pthread_create delayed until end of goenvs so that we can look at the environment first. ncpu = getncpu() physPageSize = getPageSize()}
func schedinit() { // raceinit must be the first call to race detector. // In particular, it must be done before mallocinit below calls racemapshadow. _g_ := getg() if raceenabled { _g_.racectx, raceprocctx0 = raceinit() } // 最大零碎线程数(非goroutines数) sched.maxmcount = 10000 // 栈、内存、调度器初始化 tracebackinit() moduledataverify() stackinit() mallocinit() mcommoninit(_g_.m) // 初始化CPU等 cpuinit() // must run before alginit alginit() // maps must not be used before this call modulesinit() // provides activeModules typelinksinit() // uses maps, activeModules itabsinit() // uses activeModules msigsave(_g_.m) initSigmask = _g_.m.sigmask goargs() goenvs() // 初始化调试相干 parsedebugvars() // GC gcinit() sched.lastpoll = uint64(nanotime()) procs := ncpu if n, ok := atoi32(gogetenv("GOMAXPROCS")); ok && n > 0 { procs = n } if procresize(procs) != nil { throw("unknown runnable goroutine during bootstrap") } // For cgocheck > 1, we turn on the write barrier at all times // and check all pointer writes. We can't do this until after // procresize because the write barrier needs a P. if debug.cgocheck > 1 { writeBarrier.cgo = true writeBarrier.enabled = true for _, p := range allp { p.wbBuf.reset() } } if buildVersion == "" { // Condition should never trigger. This code just serves // to ensure runtime·buildVersion is kept in the resulting binary. buildVersion = "unknown" }}
runtime.main
// The main goroutine.func main() { g := getg() // Racectx of m0->g0 is used only as the parent of the main goroutine. // It must not be used for anything else. g.m.g0.racectx = 0 // Max stack size is 1 GB on 64-bit, 250 MB on 32-bit. // Using decimal instead of binary GB and MB because // they look nicer in the stack overflow failure message. if sys.PtrSize == 8 { maxstacksize = 1000000000 } else { maxstacksize = 250000000 } // Allow newproc to start new Ms. mainStarted = true if GOARCH != "wasm" { // no threads on wasm yet, so no sysmon systemstack(func() { newm(sysmon, nil) }) } // Lock the main goroutine onto this, the main OS thread, // during initialization. Most programs won't care, but a few // do require certain calls to be made by the main thread. // Those can arrange for main.main to run in the main thread // by calling runtime.LockOSThread during initialization // to preserve the lock. lockOSThread() if g.m != &m0 { throw("runtime.main not on m0") } runtime_init() // must be before defer if nanotime() == 0 { throw("nanotime returning zero") } // Defer unlock so that runtime.Goexit during init does the unlock too. needUnlock := true defer func() { if needUnlock { unlockOSThread() } }() // Record when the world started. runtimeInitTime = nanotime() gcenable() main_init_done = make(chan bool) if iscgo { if _cgo_thread_start == nil { throw("_cgo_thread_start missing") } if GOOS != "windows" { if _cgo_setenv == nil { throw("_cgo_setenv missing") } if _cgo_unsetenv == nil { throw("_cgo_unsetenv missing") } } if _cgo_notify_runtime_init_done == nil { throw("_cgo_notify_runtime_init_done missing") } // Start the template thread in case we enter Go from // a C-created thread and need to create a new thread. startTemplateThread() cgocall(_cgo_notify_runtime_init_done, nil) } fn := main_init // make an indirect call, as the linker doesn't know the address of the main package when laying down the runtime fn() close(main_init_done) needUnlock = false unlockOSThread() if isarchive || islibrary { // A program compiled with -buildmode=c-archive or c-shared // has a main, but it is not executed. return } fn = main_main // make an indirect call, as the linker doesn't know the address of the main package when laying down the runtime fn() if raceenabled { racefini() } // Make racy client program work: if panicking on // another goroutine at the same time as main returns, // let the other goroutine finish printing the panic trace. // Once it does, it will exit. See issues 3934 and 20018. if atomic.Load(&runningPanicDefers) != 0 { // Running deferred functions should not take long. for c := 0; c < 1000; c++ { if atomic.Load(&runningPanicDefers) == 0 { break } Gosched() } } if atomic.Load(&panicking) != 0 { gopark(nil, nil, waitReasonPanicWait, traceEvGoStop, 1) } exit(0) for { var x *int32 *x = 0 }}