rollup merge of #19454: nodakai/libstd-reap-failed-child
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 in `libstd/io/process.rs` calls the ps command to check if the new code can really reap a zombie. 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 ... ``` where `./spawn-failure` is my test program which intentionally leaves many zombies. 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.
This commit is contained in:
commit
64d58dcac2
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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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@ -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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