gogo
gogo由汇编实现，次要是由g0切换到g栈，而后执行函数。
// func gogo(buf *gobuf)// restore state from Gobuf; longjmpTEXT runtime·gogo(SB), NOSPLIT, $16-8 MOVQ buf+0(FP), BX // gobuf MOVQ gobuf_g(BX), DX MOVQ 0(DX), CX // make sure g != nil get_tls(CX) MOVQ DX, g(CX) MOVQ gobuf_sp(BX), SP // restore SP, 复原sp寄存器值切换到g栈 MOVQ gobuf_ret(BX), AX MOVQ gobuf_ctxt(BX), DX MOVQ gobuf_bp(BX), BP MOVQ $0, gobuf_sp(BX) // clear to help garbage collector MOVQ $0, gobuf_ret(BX) MOVQ $0, gobuf_ctxt(BX) MOVQ $0, gobuf_bp(BX) MOVQ gobuf_pc(BX), BX // 获取G工作函数的地址 JMP BX // 转到工作函数执行goexit
当调用工作函数完结返回的时候，会执行到咱们在创立g流程中就初始化好的指令：goexit
TEXT runtime·goexit(SB),NOSPLIT,$0-0 BYTE $0x90 // NOP CALL runtime·goexit1(SB) // does not return 调用goexit1函数 // traceback from goexit1 must hit code range of goexit BYTE $0x90 // NOP // Finishes execution of the current goroutine.func goexit1() { if raceenabled { racegoend() } if trace.enabled { traceGoEnd() } mcall(goexit0) // 切换到g0执行goexit0}// goexit continuation on g0.func goexit0(gp *g) { _g_ := getg() // gp的状态置为_Gdead casgstatus(gp, _Grunning, _Gdead) if isSystemGoroutine(gp, false) { atomic.Xadd(&sched.ngsys, -1) } // 状态重置 gp.m = nil // G和M是否锁定 locked := gp.lockedm != 0 // G和M解除锁定 gp.lockedm = 0 _g_.m.lockedg = 0 gp.preemptStop = false gp.paniconfault = false gp._defer = nil // should be true already but just in case. gp._panic = nil // non-nil for Goexit during panic. points at stack-allocated data. gp.writebuf = nil gp.waitreason = 0 gp.param = nil gp.labels = nil gp.timer = nil if gcBlackenEnabled != 0 && gp.gcAssistBytes > 0 { // Flush assist credit to the global pool. This gives // better information to pacing if the application is // rapidly creating an exiting goroutines. assistWorkPerByte := float64frombits(atomic.Load64(&gcController.assistWorkPerByte)) scanCredit := int64(assistWorkPerByte * float64(gp.gcAssistBytes)) atomic.Xaddint64(&gcController.bgScanCredit, scanCredit) gp.gcAssistBytes = 0 } // 解决G和M的革除工作 dropg() if GOARCH == "wasm" { // no threads yet on wasm gfput(_g_.m.p.ptr(), gp) schedule() // never returns } if _g_.m.lockedInt != 0 { print("invalid m->lockedInt = ", _g_.m.lockedInt, "\n") throw("internal lockOSThread error") } // 将G放入P的G闲暇链表 gfput(_g_.m.p.ptr(), gp) if locked { // The goroutine may have locked this thread because // it put it in an unusual kernel state. Kill it // rather than returning it to the thread pool. // Return to mstart, which will release the P and exit // the thread. if GOOS != "plan9" { // See golang.org/issue/22227. gogo(&_g_.m.g0.sched) } else { // Clear lockedExt on plan9 since we may end up re-using // this thread. _g_.m.lockedExt = 0 } } // 再次进入调度 schedule()}