wait_waitid.go

     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  // We used to use this code for Darwin, but according to issue #19314
     6  // waitid returns if the process is stopped, even when using WEXITED.
     7  
     8  //go:build linux
     9  
    10  package os
    11  
    12  import (
    13  	"runtime"
    14  	"syscall"
    15  	"unsafe"
    16  )
    17  
    18  const _P_PID = 1
    19  
    20  // blockUntilWaitable attempts to block until a call to p.Wait will
    21  // succeed immediately, and reports whether it has done so.
    22  // It does not actually call p.Wait.
    23  func (p *Process) blockUntilWaitable() (bool, error) {
    24  	// The waitid system call expects a pointer to a siginfo_t,
    25  	// which is 128 bytes on all Linux systems.
    26  	// On darwin/amd64, it requires 104 bytes.
    27  	// We don't care about the values it returns.
    28  	var siginfo [16]uint64
    29  	psig := &siginfo[0]
    30  	var e syscall.Errno
    31  	for {
    32  		_, _, e = syscall.Syscall6(syscall.SYS_WAITID, _P_PID, uintptr(p.Pid), uintptr(unsafe.Pointer(psig)), syscall.WEXITED|syscall.WNOWAIT, 0, 0)
    33  		if e != syscall.EINTR {
    34  			break
    35  		}
    36  	}
    37  	runtime.KeepAlive(p)
    38  	if e != 0 {
    39  		// waitid has been available since Linux 2.6.9, but
    40  		// reportedly is not available in Ubuntu on Windows.
    41  		// See issue 16610.
    42  		if e == syscall.ENOSYS {
    43  			return false, nil
    44  		}
    45  		return false, NewSyscallError("waitid", e)
    46  	}
    47  	return true, nil
    48  }
    49
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