github.com/c0deoo1/golang1.5@v0.0.0-20220525150107-c87c805d4593/src/runtime/os3_solaris.go (about)

     1  // Copyright 2011 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 "unsafe"
     8  
     9  //go:cgo_export_dynamic runtime.end _end
    10  //go:cgo_export_dynamic runtime.etext _etext
    11  //go:cgo_export_dynamic runtime.edata _edata
    12  
    13  //go:cgo_import_dynamic libc____errno ___errno "libc.so"
    14  //go:cgo_import_dynamic libc_clock_gettime clock_gettime "libc.so"
    15  //go:cgo_import_dynamic libc_close close "libc.so"
    16  //go:cgo_import_dynamic libc_exit exit "libc.so"
    17  //go:cgo_import_dynamic libc_fstat fstat "libc.so"
    18  //go:cgo_import_dynamic libc_getcontext getcontext "libc.so"
    19  //go:cgo_import_dynamic libc_getrlimit getrlimit "libc.so"
    20  //go:cgo_import_dynamic libc_kill kill "libc.so"
    21  //go:cgo_import_dynamic libc_madvise madvise "libc.so"
    22  //go:cgo_import_dynamic libc_malloc malloc "libc.so"
    23  //go:cgo_import_dynamic libc_mmap mmap "libc.so"
    24  //go:cgo_import_dynamic libc_munmap munmap "libc.so"
    25  //go:cgo_import_dynamic libc_open open "libc.so"
    26  //go:cgo_import_dynamic libc_pthread_attr_destroy pthread_attr_destroy "libc.so"
    27  //go:cgo_import_dynamic libc_pthread_attr_getstack pthread_attr_getstack "libc.so"
    28  //go:cgo_import_dynamic libc_pthread_attr_init pthread_attr_init "libc.so"
    29  //go:cgo_import_dynamic libc_pthread_attr_setdetachstate pthread_attr_setdetachstate "libc.so"
    30  //go:cgo_import_dynamic libc_pthread_attr_setstack pthread_attr_setstack "libc.so"
    31  //go:cgo_import_dynamic libc_pthread_create pthread_create "libc.so"
    32  //go:cgo_import_dynamic libc_raise raise "libc.so"
    33  //go:cgo_import_dynamic libc_read read "libc.so"
    34  //go:cgo_import_dynamic libc_select select "libc.so"
    35  //go:cgo_import_dynamic libc_sched_yield sched_yield "libc.so"
    36  //go:cgo_import_dynamic libc_sem_init sem_init "libc.so"
    37  //go:cgo_import_dynamic libc_sem_post sem_post "libc.so"
    38  //go:cgo_import_dynamic libc_sem_reltimedwait_np sem_reltimedwait_np "libc.so"
    39  //go:cgo_import_dynamic libc_sem_wait sem_wait "libc.so"
    40  //go:cgo_import_dynamic libc_setitimer setitimer "libc.so"
    41  //go:cgo_import_dynamic libc_sigaction sigaction "libc.so"
    42  //go:cgo_import_dynamic libc_sigaltstack sigaltstack "libc.so"
    43  //go:cgo_import_dynamic libc_sigprocmask sigprocmask "libc.so"
    44  //go:cgo_import_dynamic libc_sysconf sysconf "libc.so"
    45  //go:cgo_import_dynamic libc_usleep usleep "libc.so"
    46  //go:cgo_import_dynamic libc_write write "libc.so"
    47  
    48  //go:linkname libc____errno libc____errno
    49  //go:linkname libc_clock_gettime libc_clock_gettime
    50  //go:linkname libc_close libc_close
    51  //go:linkname libc_exit libc_exit
    52  //go:linkname libc_fstat libc_fstat
    53  //go:linkname libc_getcontext libc_getcontext
    54  //go:linkname libc_getrlimit libc_getrlimit
    55  //go:linkname libc_kill libc_kill
    56  //go:linkname libc_madvise libc_madvise
    57  //go:linkname libc_malloc libc_malloc
    58  //go:linkname libc_mmap libc_mmap
    59  //go:linkname libc_munmap libc_munmap
    60  //go:linkname libc_open libc_open
    61  //go:linkname libc_pthread_attr_destroy libc_pthread_attr_destroy
    62  //go:linkname libc_pthread_attr_getstack libc_pthread_attr_getstack
    63  //go:linkname libc_pthread_attr_init libc_pthread_attr_init
    64  //go:linkname libc_pthread_attr_setdetachstate libc_pthread_attr_setdetachstate
    65  //go:linkname libc_pthread_attr_setstack libc_pthread_attr_setstack
    66  //go:linkname libc_pthread_create libc_pthread_create
    67  //go:linkname libc_raise libc_raise
    68  //go:linkname libc_read libc_read
    69  //go:linkname libc_select libc_select
    70  //go:linkname libc_sched_yield libc_sched_yield
    71  //go:linkname libc_sem_init libc_sem_init
    72  //go:linkname libc_sem_post libc_sem_post
    73  //go:linkname libc_sem_reltimedwait_np libc_sem_reltimedwait_np
    74  //go:linkname libc_sem_wait libc_sem_wait
    75  //go:linkname libc_setitimer libc_setitimer
    76  //go:linkname libc_sigaction libc_sigaction
    77  //go:linkname libc_sigaltstack libc_sigaltstack
    78  //go:linkname libc_sigprocmask libc_sigprocmask
    79  //go:linkname libc_sysconf libc_sysconf
    80  //go:linkname libc_usleep libc_usleep
    81  //go:linkname libc_write libc_write
    82  
    83  var (
    84  	libc____errno,
    85  	libc_clock_gettime,
    86  	libc_close,
    87  	libc_exit,
    88  	libc_fstat,
    89  	libc_getcontext,
    90  	libc_getrlimit,
    91  	libc_kill,
    92  	libc_madvise,
    93  	libc_malloc,
    94  	libc_mmap,
    95  	libc_munmap,
    96  	libc_open,
    97  	libc_pthread_attr_destroy,
    98  	libc_pthread_attr_getstack,
    99  	libc_pthread_attr_init,
   100  	libc_pthread_attr_setdetachstate,
   101  	libc_pthread_attr_setstack,
   102  	libc_pthread_create,
   103  	libc_raise,
   104  	libc_read,
   105  	libc_sched_yield,
   106  	libc_select,
   107  	libc_sem_init,
   108  	libc_sem_post,
   109  	libc_sem_reltimedwait_np,
   110  	libc_sem_wait,
   111  	libc_setitimer,
   112  	libc_sigaction,
   113  	libc_sigaltstack,
   114  	libc_sigprocmask,
   115  	libc_sysconf,
   116  	libc_usleep,
   117  	libc_write libcFunc
   118  )
   119  
   120  var sigset_all = sigset{[4]uint32{^uint32(0), ^uint32(0), ^uint32(0), ^uint32(0)}}
   121  
   122  func getncpu() int32 {
   123  	n := int32(sysconf(__SC_NPROCESSORS_ONLN))
   124  	if n < 1 {
   125  		return 1
   126  	}
   127  	return n
   128  }
   129  
   130  func osinit() {
   131  	ncpu = getncpu()
   132  }
   133  
   134  func tstart_sysvicall()
   135  
   136  // May run with m.p==nil, so write barriers are not allowed.
   137  //go:nowritebarrier
   138  func newosproc(mp *m, _ unsafe.Pointer) {
   139  	var (
   140  		attr pthreadattr
   141  		oset sigset
   142  		tid  pthread
   143  		ret  int32
   144  		size uint64
   145  	)
   146  
   147  	if pthread_attr_init(&attr) != 0 {
   148  		throw("pthread_attr_init")
   149  	}
   150  	if pthread_attr_setstack(&attr, 0, 0x200000) != 0 {
   151  		throw("pthread_attr_setstack")
   152  	}
   153  	if pthread_attr_getstack(&attr, unsafe.Pointer(&mp.g0.stack.hi), &size) != 0 {
   154  		throw("pthread_attr_getstack")
   155  	}
   156  	mp.g0.stack.lo = mp.g0.stack.hi - uintptr(size)
   157  	if pthread_attr_setdetachstate(&attr, _PTHREAD_CREATE_DETACHED) != 0 {
   158  		throw("pthread_attr_setdetachstate")
   159  	}
   160  
   161  	// Disable signals during create, so that the new thread starts
   162  	// with signals disabled.  It will enable them in minit.
   163  	sigprocmask(_SIG_SETMASK, &sigset_all, &oset)
   164  	ret = pthread_create(&tid, &attr, funcPC(tstart_sysvicall), unsafe.Pointer(mp))
   165  	sigprocmask(_SIG_SETMASK, &oset, nil)
   166  	if ret != 0 {
   167  		print("runtime: failed to create new OS thread (have ", mcount(), " already; errno=", ret, ")\n")
   168  		throw("newosproc")
   169  	}
   170  }
   171  
   172  var urandom_dev = []byte("/dev/urandom\x00")
   173  
   174  //go:nosplit
   175  func getRandomData(r []byte) {
   176  	fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
   177  	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
   178  	closefd(fd)
   179  	extendRandom(r, int(n))
   180  }
   181  
   182  func goenvs() {
   183  	goenvs_unix()
   184  }
   185  
   186  // Called to initialize a new m (including the bootstrap m).
   187  // Called on the parent thread (main thread in case of bootstrap), can allocate memory.
   188  func mpreinit(mp *m) {
   189  	mp.gsignal = malg(32 * 1024)
   190  	mp.gsignal.m = mp
   191  }
   192  
   193  func miniterrno()
   194  
   195  func msigsave(mp *m) {
   196  	smask := (*sigset)(unsafe.Pointer(&mp.sigmask))
   197  	if unsafe.Sizeof(*smask) > unsafe.Sizeof(mp.sigmask) {
   198  		throw("insufficient storage for signal mask")
   199  	}
   200  	sigprocmask(_SIG_SETMASK, nil, smask)
   201  }
   202  
   203  // Called to initialize a new m (including the bootstrap m).
   204  // Called on the new thread, can not allocate memory.
   205  func minit() {
   206  	_g_ := getg()
   207  	asmcgocall(unsafe.Pointer(funcPC(miniterrno)), unsafe.Pointer(&libc____errno))
   208  	// Initialize signal handling
   209  	signalstack(&_g_.m.gsignal.stack)
   210  
   211  	// restore signal mask from m.sigmask and unblock essential signals
   212  	nmask := *(*sigset)(unsafe.Pointer(&_g_.m.sigmask))
   213  	for i := range sigtable {
   214  		if sigtable[i].flags&_SigUnblock != 0 {
   215  			nmask.__sigbits[(i-1)/32] &^= 1 << ((uint32(i) - 1) & 31)
   216  		}
   217  	}
   218  	sigprocmask(_SIG_SETMASK, &nmask, nil)
   219  }
   220  
   221  // Called from dropm to undo the effect of an minit.
   222  func unminit() {
   223  	_g_ := getg()
   224  	smask := (*sigset)(unsafe.Pointer(&_g_.m.sigmask))
   225  	sigprocmask(_SIG_SETMASK, smask, nil)
   226  
   227  	signalstack(nil)
   228  }
   229  
   230  func memlimit() uintptr {
   231  	/*
   232  		TODO: Convert to Go when something actually uses the result.
   233  		Rlimit rl;
   234  		extern byte runtime·text[], runtime·end[];
   235  		uintptr used;
   236  
   237  		if(runtime·getrlimit(RLIMIT_AS, &rl) != 0)
   238  			return 0;
   239  		if(rl.rlim_cur >= 0x7fffffff)
   240  			return 0;
   241  
   242  		// Estimate our VM footprint excluding the heap.
   243  		// Not an exact science: use size of binary plus
   244  		// some room for thread stacks.
   245  		used = runtime·end - runtime·text + (64<<20);
   246  		if(used >= rl.rlim_cur)
   247  			return 0;
   248  
   249  		// If there's not at least 16 MB left, we're probably
   250  		// not going to be able to do much.  Treat as no limit.
   251  		rl.rlim_cur -= used;
   252  		if(rl.rlim_cur < (16<<20))
   253  			return 0;
   254  
   255  		return rl.rlim_cur - used;
   256  	*/
   257  
   258  	return 0
   259  }
   260  
   261  func sigtramp()
   262  
   263  func setsig(i int32, fn uintptr, restart bool) {
   264  	var sa sigactiont
   265  
   266  	sa.sa_flags = _SA_SIGINFO | _SA_ONSTACK
   267  	sa.sa_flags = _SA_SIGINFO | _SA_ONSTACK
   268  	if restart {
   269  		sa.sa_flags |= _SA_RESTART
   270  	}
   271  	sa.sa_mask = sigset_all
   272  	if fn == funcPC(sighandler) {
   273  		fn = funcPC(sigtramp)
   274  	}
   275  	*((*uintptr)(unsafe.Pointer(&sa._funcptr))) = fn
   276  	sigaction(i, &sa, nil)
   277  }
   278  
   279  func setsigstack(i int32) {
   280  	throw("setsigstack")
   281  }
   282  
   283  func getsig(i int32) uintptr {
   284  	var sa sigactiont
   285  	sigaction(i, nil, &sa)
   286  	if *((*uintptr)(unsafe.Pointer(&sa._funcptr))) == funcPC(sigtramp) {
   287  		return funcPC(sighandler)
   288  	}
   289  	return *((*uintptr)(unsafe.Pointer(&sa._funcptr)))
   290  }
   291  
   292  func signalstack(s *stack) {
   293  	var st sigaltstackt
   294  	if s == nil {
   295  		st.ss_flags = _SS_DISABLE
   296  	} else {
   297  		st.ss_sp = (*byte)(unsafe.Pointer(s.lo))
   298  		st.ss_size = uint64(s.hi - s.lo)
   299  		st.ss_flags = 0
   300  	}
   301  	sigaltstack(&st, nil)
   302  }
   303  
   304  func updatesigmask(m sigmask) {
   305  	var mask sigset
   306  	copy(mask.__sigbits[:], m[:])
   307  	sigprocmask(_SIG_SETMASK, &mask, nil)
   308  }
   309  
   310  func unblocksig(sig int32) {
   311  	var mask sigset
   312  	mask.__sigbits[(sig-1)/32] |= 1 << ((uint32(sig) - 1) & 31)
   313  	sigprocmask(_SIG_UNBLOCK, &mask, nil)
   314  }
   315  
   316  //go:nosplit
   317  func semacreate() uintptr {
   318  	var sem *semt
   319  	_g_ := getg()
   320  
   321  	// Call libc's malloc rather than malloc.  This will
   322  	// allocate space on the C heap.  We can't call malloc
   323  	// here because it could cause a deadlock.
   324  	_g_.m.libcall.fn = uintptr(unsafe.Pointer(&libc_malloc))
   325  	_g_.m.libcall.n = 1
   326  	memclr(unsafe.Pointer(&_g_.m.scratch), uintptr(len(_g_.m.scratch.v)))
   327  	_g_.m.scratch.v[0] = unsafe.Sizeof(*sem)
   328  	_g_.m.libcall.args = uintptr(unsafe.Pointer(&_g_.m.scratch))
   329  	asmcgocall(unsafe.Pointer(&asmsysvicall6), unsafe.Pointer(&_g_.m.libcall))
   330  	sem = (*semt)(unsafe.Pointer(_g_.m.libcall.r1))
   331  	if sem_init(sem, 0, 0) != 0 {
   332  		throw("sem_init")
   333  	}
   334  	return uintptr(unsafe.Pointer(sem))
   335  }
   336  
   337  //go:nosplit
   338  func semasleep(ns int64) int32 {
   339  	_m_ := getg().m
   340  	if ns >= 0 {
   341  		_m_.ts.tv_sec = ns / 1000000000
   342  		_m_.ts.tv_nsec = ns % 1000000000
   343  
   344  		_m_.libcall.fn = uintptr(unsafe.Pointer(&libc_sem_reltimedwait_np))
   345  		_m_.libcall.n = 2
   346  		memclr(unsafe.Pointer(&_m_.scratch), uintptr(len(_m_.scratch.v)))
   347  		_m_.scratch.v[0] = _m_.waitsema
   348  		_m_.scratch.v[1] = uintptr(unsafe.Pointer(&_m_.ts))
   349  		_m_.libcall.args = uintptr(unsafe.Pointer(&_m_.scratch))
   350  		asmcgocall(unsafe.Pointer(&asmsysvicall6), unsafe.Pointer(&_m_.libcall))
   351  		if *_m_.perrno != 0 {
   352  			if *_m_.perrno == _ETIMEDOUT || *_m_.perrno == _EAGAIN || *_m_.perrno == _EINTR {
   353  				return -1
   354  			}
   355  			throw("sem_reltimedwait_np")
   356  		}
   357  		return 0
   358  	}
   359  	for {
   360  		_m_.libcall.fn = uintptr(unsafe.Pointer(&libc_sem_wait))
   361  		_m_.libcall.n = 1
   362  		memclr(unsafe.Pointer(&_m_.scratch), uintptr(len(_m_.scratch.v)))
   363  		_m_.scratch.v[0] = _m_.waitsema
   364  		_m_.libcall.args = uintptr(unsafe.Pointer(&_m_.scratch))
   365  		asmcgocall(unsafe.Pointer(&asmsysvicall6), unsafe.Pointer(&_m_.libcall))
   366  		if _m_.libcall.r1 == 0 {
   367  			break
   368  		}
   369  		if *_m_.perrno == _EINTR {
   370  			continue
   371  		}
   372  		throw("sem_wait")
   373  	}
   374  	return 0
   375  }
   376  
   377  //go:nosplit
   378  func semawakeup(mp *m) {
   379  	if sem_post((*semt)(unsafe.Pointer(mp.waitsema))) != 0 {
   380  		throw("sem_post")
   381  	}
   382  }
   383  
   384  //go:nosplit
   385  func closefd(fd int32) int32 {
   386  	return int32(sysvicall1(&libc_close, uintptr(fd)))
   387  }
   388  
   389  //go:nosplit
   390  func exit(r int32) {
   391  	sysvicall1(&libc_exit, uintptr(r))
   392  }
   393  
   394  //go:nosplit
   395  func getcontext(context *ucontext) /* int32 */ {
   396  	sysvicall1(&libc_getcontext, uintptr(unsafe.Pointer(context)))
   397  }
   398  
   399  //go:nosplit
   400  func madvise(addr unsafe.Pointer, n uintptr, flags int32) {
   401  	sysvicall3(&libc_madvise, uintptr(addr), uintptr(n), uintptr(flags))
   402  }
   403  
   404  //go:nosplit
   405  func mmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) unsafe.Pointer {
   406  	return unsafe.Pointer(sysvicall6(&libc_mmap, uintptr(addr), uintptr(n), uintptr(prot), uintptr(flags), uintptr(fd), uintptr(off)))
   407  }
   408  
   409  //go:nosplit
   410  func munmap(addr unsafe.Pointer, n uintptr) {
   411  	sysvicall2(&libc_munmap, uintptr(addr), uintptr(n))
   412  }
   413  
   414  func nanotime1()
   415  
   416  //go:nosplit
   417  func nanotime() int64 {
   418  	return int64(sysvicall0((*libcFunc)(unsafe.Pointer(funcPC(nanotime1)))))
   419  }
   420  
   421  //go:nosplit
   422  func open(path *byte, mode, perm int32) int32 {
   423  	return int32(sysvicall3(&libc_open, uintptr(unsafe.Pointer(path)), uintptr(mode), uintptr(perm)))
   424  }
   425  
   426  func pthread_attr_destroy(attr *pthreadattr) int32 {
   427  	return int32(sysvicall1(&libc_pthread_attr_destroy, uintptr(unsafe.Pointer(attr))))
   428  }
   429  
   430  func pthread_attr_getstack(attr *pthreadattr, addr unsafe.Pointer, size *uint64) int32 {
   431  	return int32(sysvicall3(&libc_pthread_attr_getstack, uintptr(unsafe.Pointer(attr)), uintptr(addr), uintptr(unsafe.Pointer(size))))
   432  }
   433  
   434  func pthread_attr_init(attr *pthreadattr) int32 {
   435  	return int32(sysvicall1(&libc_pthread_attr_init, uintptr(unsafe.Pointer(attr))))
   436  }
   437  
   438  func pthread_attr_setdetachstate(attr *pthreadattr, state int32) int32 {
   439  	return int32(sysvicall2(&libc_pthread_attr_setdetachstate, uintptr(unsafe.Pointer(attr)), uintptr(state)))
   440  }
   441  
   442  func pthread_attr_setstack(attr *pthreadattr, addr uintptr, size uint64) int32 {
   443  	return int32(sysvicall3(&libc_pthread_attr_setstack, uintptr(unsafe.Pointer(attr)), uintptr(addr), uintptr(size)))
   444  }
   445  
   446  func pthread_create(thread *pthread, attr *pthreadattr, fn uintptr, arg unsafe.Pointer) int32 {
   447  	return int32(sysvicall4(&libc_pthread_create, uintptr(unsafe.Pointer(thread)), uintptr(unsafe.Pointer(attr)), uintptr(fn), uintptr(arg)))
   448  }
   449  
   450  func raise(sig int32) /* int32 */ {
   451  	sysvicall1(&libc_raise, uintptr(sig))
   452  }
   453  
   454  func raiseproc(sig int32) /* int32 */ {
   455  	pid := sysvicall0(&libc_getpid)
   456  	sysvicall2(&libc_kill, pid, uintptr(sig))
   457  }
   458  
   459  //go:nosplit
   460  func read(fd int32, buf unsafe.Pointer, nbyte int32) int32 {
   461  	return int32(sysvicall3(&libc_read, uintptr(fd), uintptr(buf), uintptr(nbyte)))
   462  }
   463  
   464  //go:nosplit
   465  func sem_init(sem *semt, pshared int32, value uint32) int32 {
   466  	return int32(sysvicall3(&libc_sem_init, uintptr(unsafe.Pointer(sem)), uintptr(pshared), uintptr(value)))
   467  }
   468  
   469  //go:nosplit
   470  func sem_post(sem *semt) int32 {
   471  	return int32(sysvicall1(&libc_sem_post, uintptr(unsafe.Pointer(sem))))
   472  }
   473  
   474  //go:nosplit
   475  func sem_reltimedwait_np(sem *semt, timeout *timespec) int32 {
   476  	return int32(sysvicall2(&libc_sem_reltimedwait_np, uintptr(unsafe.Pointer(sem)), uintptr(unsafe.Pointer(timeout))))
   477  }
   478  
   479  //go:nosplit
   480  func sem_wait(sem *semt) int32 {
   481  	return int32(sysvicall1(&libc_sem_wait, uintptr(unsafe.Pointer(sem))))
   482  }
   483  
   484  func setitimer(which int32, value *itimerval, ovalue *itimerval) /* int32 */ {
   485  	sysvicall3(&libc_setitimer, uintptr(which), uintptr(unsafe.Pointer(value)), uintptr(unsafe.Pointer(ovalue)))
   486  }
   487  
   488  func sigaction(sig int32, act *sigactiont, oact *sigactiont) /* int32 */ {
   489  	sysvicall3(&libc_sigaction, uintptr(sig), uintptr(unsafe.Pointer(act)), uintptr(unsafe.Pointer(oact)))
   490  }
   491  
   492  func sigaltstack(ss *sigaltstackt, oss *sigaltstackt) /* int32 */ {
   493  	sysvicall2(&libc_sigaltstack, uintptr(unsafe.Pointer(ss)), uintptr(unsafe.Pointer(oss)))
   494  }
   495  
   496  func sigprocmask(how int32, set *sigset, oset *sigset) /* int32 */ {
   497  	sysvicall3(&libc_sigprocmask, uintptr(how), uintptr(unsafe.Pointer(set)), uintptr(unsafe.Pointer(oset)))
   498  }
   499  
   500  func sysconf(name int32) int64 {
   501  	return int64(sysvicall1(&libc_sysconf, uintptr(name)))
   502  }
   503  
   504  func usleep1(uint32)
   505  
   506  //go:nosplit
   507  func usleep(µs uint32) {
   508  	usleep1(µs)
   509  }
   510  
   511  //go:nosplit
   512  func write(fd uintptr, buf unsafe.Pointer, nbyte int32) int32 {
   513  	return int32(sysvicall3(&libc_write, uintptr(fd), uintptr(buf), uintptr(nbyte)))
   514  }
   515  
   516  func osyield1()
   517  
   518  //go:nosplit
   519  func osyield() {
   520  	_g_ := getg()
   521  
   522  	// Check the validity of m because we might be called in cgo callback
   523  	// path early enough where there isn't a m available yet.
   524  	if _g_ != nil && _g_.m != nil {
   525  		sysvicall0(&libc_sched_yield)
   526  		return
   527  	}
   528  	osyield1()
   529  }