libstd/sys/unix/process.rs: reap a zombie who didn't get through to exec(2).
After the library successfully called fork(2), the child does several setup works such as setting UID, GID and current directory before it calls exec(2). When those setup works failed, the child exits but the parent didn't call waitpid(2) and left it as a zombie. This patch also add several sanity checks. They shouldn't make any noticeable impact to runtime performance. The new test case run-pass/wait-forked-but-failed-child.rs calls the ps command to check if the new code can really reap a zombie. When I intentionally create many zombies with my test program ./spawn-failure, The output of "ps -A -o pid,sid,command" should look like this: PID SID COMMAND 1 1 /sbin/init 2 0 [kthreadd] 3 0 [ksoftirqd/0] ... 12562 9237 ./spawn-failure 12563 9237 [spawn-failure] <defunct> 12564 9237 [spawn-failure] <defunct> ... 12592 9237 [spawn-failure] <defunct> 12593 9237 ps -A -o pid,sid,command 12884 12884 /bin/zsh 12922 12922 /bin/zsh ... Filtering the output with the "SID" (session ID) column is a quick way to tell if a process (zombie) was spawned by my own test program. Then the number of "defunct" lines is the number of zombie children. Signed-off-by: NODA, Kai <nodakai@gmail.com>
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@ -11,7 +11,7 @@ use self::Req::*;
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use libc::{mod, pid_t, c_void, c_int};
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use c_str::CString;
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use io::{mod, IoResult, IoError};
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use io::{mod, IoResult, IoError, EndOfFile};
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use mem;
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use os;
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use ptr;
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@ -39,6 +39,8 @@ enum Req {
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NewChild(libc::pid_t, Sender<ProcessExit>, u64),
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}
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const CLOEXEC_MSG_FOOTER: &'static [u8] = b"NOEX";
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impl Process {
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pub fn id(&self) -> pid_t {
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self.pid
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@ -106,18 +108,36 @@ impl Process {
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if pid < 0 {
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return Err(super::last_error())
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} else if pid > 0 {
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#[inline]
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fn combine(arr: &[u8]) -> i32 {
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let a = arr[0] as u32;
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let b = arr[1] as u32;
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let c = arr[2] as u32;
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let d = arr[3] as u32;
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((a << 24) | (b << 16) | (c << 8) | (d << 0)) as i32
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}
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let p = Process{ pid: pid };
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drop(output);
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let mut bytes = [0, ..4];
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let mut bytes = [0, ..8];
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return match input.read(&mut bytes) {
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Ok(4) => {
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let errno = (bytes[0] as i32 << 24) |
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(bytes[1] as i32 << 16) |
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(bytes[2] as i32 << 8) |
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(bytes[3] as i32 << 0);
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Ok(8) => {
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assert!(combine(CLOEXEC_MSG_FOOTER) == combine(bytes.slice(4, 8)),
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"Validation on the CLOEXEC pipe failed: {}", bytes);
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let errno = combine(bytes.slice(0, 4));
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assert!(p.wait(0).is_ok(), "wait(0) should either return Ok or panic");
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Err(super::decode_error(errno))
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}
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Err(..) => Ok(Process { pid: pid }),
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Ok(..) => panic!("short read on the cloexec pipe"),
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Err(ref e) if e.kind == EndOfFile => Ok(p),
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Err(e) => {
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assert!(p.wait(0).is_ok(), "wait(0) should either return Ok or panic");
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panic!("the CLOEXEC pipe failed: {}", e)
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},
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Ok(..) => { // pipe I/O up to PIPE_BUF bytes should be atomic
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assert!(p.wait(0).is_ok(), "wait(0) should either return Ok or panic");
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panic!("short read on the CLOEXEC pipe")
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}
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};
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}
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@ -154,13 +174,16 @@ impl Process {
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let _ = libc::close(input.fd());
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fn fail(output: &mut FileDesc) -> ! {
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let errno = sys::os::errno();
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let errno = sys::os::errno() as u32;
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let bytes = [
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(errno >> 24) as u8,
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(errno >> 16) as u8,
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(errno >> 8) as u8,
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(errno >> 0) as u8,
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CLOEXEC_MSG_FOOTER[0], CLOEXEC_MSG_FOOTER[1],
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CLOEXEC_MSG_FOOTER[2], CLOEXEC_MSG_FOOTER[3]
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];
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// pipe I/O up to PIPE_BUF bytes should be atomic
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assert!(output.write(&bytes).is_ok());
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unsafe { libc::_exit(1) }
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}
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79
src/test/run-pass/wait-forked-but-failed-child.rs
Normal file
79
src/test/run-pass/wait-forked-but-failed-child.rs
Normal file
@ -0,0 +1,79 @@
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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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extern crate libc;
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use std::io::process::Command;
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use std::iter::IteratorExt;
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use libc::funcs::posix88::unistd;
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// "ps -A -o pid,sid,command" with GNU ps should output something like this:
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// PID SID COMMAND
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// 1 1 /sbin/init
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// 2 0 [kthreadd]
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// 3 0 [ksoftirqd/0]
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// ...
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// 12562 9237 ./spawn-failure
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// 12563 9237 [spawn-failure] <defunct>
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// 12564 9237 [spawn-failure] <defunct>
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// ...
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// 12592 9237 [spawn-failure] <defunct>
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// 12593 9237 ps -A -o pid,sid,command
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// 12884 12884 /bin/zsh
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// 12922 12922 /bin/zsh
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// ...
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#[cfg(unix)]
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fn find_zombies() {
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// http://man.freebsd.org/ps(1)
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// http://man7.org/linux/man-pages/man1/ps.1.html
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#[cfg(not(target_os = "macos"))]
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const FIELDS: &'static str = "pid,sid,command";
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// https://developer.apple.com/library/mac/documentation/Darwin/
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// Reference/ManPages/man1/ps.1.html
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#[cfg(target_os = "macos")]
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const FIELDS: &'static str = "pid,sess,command";
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let my_sid = unsafe { unistd::getsid(0) };
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let ps_cmd_output = Command::new("ps").args(&["-A", "-o", FIELDS]).output().unwrap();
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let ps_output = String::from_utf8_lossy(ps_cmd_output.output.as_slice());
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let found = ps_output.split('\n').enumerate().any(|(line_no, line)|
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0 < line_no && 0 < line.len() &&
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my_sid == from_str(line.split(' ').filter(|w| 0 < w.len()).nth(1)
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.expect("1st column should be Session ID")
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).expect("Session ID string into integer") &&
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line.contains("defunct") && {
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println!("Zombie child {}", line);
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true
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}
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);
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assert!( ! found, "Found at least one zombie child");
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}
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#[cfg(windows)]
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fn find_zombies() { }
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fn main() {
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let too_long = format!("/NoSuchCommand{:0300}", 0u8);
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for _ in range(0u32, 100) {
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let invalid = Command::new(too_long.as_slice()).spawn();
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assert!(invalid.is_err());
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}
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find_zombies();
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}
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