github.com/riscv/riscv-go@v0.0.0-20200123204226-124ebd6fcc8e/src/os/wait_waitid.go (about)

     1  // Copyright 2016 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  // +build darwin linux
     6  
     7  package os
     8  
     9  import (
    10  	"runtime"
    11  	"syscall"
    12  	"unsafe"
    13  )
    14  
    15  const _P_PID = 1
    16  
    17  // blockUntilWaitable attempts to block until a call to p.Wait will
    18  // succeed immediately, and returns whether it has done so.
    19  // It does not actually call p.Wait.
    20  func (p *Process) blockUntilWaitable() (bool, error) {
    21  	// The waitid system call expects a pointer to a siginfo_t,
    22  	// which is 128 bytes on all GNU/Linux systems.
    23  	// On Darwin, it requires greater than or equal to 64 bytes
    24  	// for darwin/{386,arm} and 104 bytes for darwin/amd64.
    25  	// We don't care about the values it returns.
    26  	var siginfo [128]byte
    27  	psig := &siginfo[0]
    28  	_, _, e := syscall.Syscall6(syscall.SYS_WAITID, _P_PID, uintptr(p.Pid), uintptr(unsafe.Pointer(psig)), syscall.WEXITED|syscall.WNOWAIT, 0, 0)
    29  	runtime.KeepAlive(p)
    30  	if e != 0 {
    31  		// waitid has been available since Linux 2.6.9, but
    32  		// reportedly is not available in Ubuntu on Windows.
    33  		// See issue 16610.
    34  		if e == syscall.ENOSYS {
    35  			return false, nil
    36  		}
    37  		return false, NewSyscallError("waitid", e)
    38  	}
    39  	return true, nil
    40  }