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tools::daemon: sync with child after MainPid message

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Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
This commit is contained in:
Wolfgang Bumiller 2020-06-22 10:58:04 +02:00
parent c40440092d
commit c08fac4d69
1 changed files with 28 additions and 11 deletions
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39
src/tools/daemon.rs
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@ -2,6 +2,7 @@
use std::ffi::CString;
use std::future::Future;
use std::io::{Read, Write};
use std::os::raw::{c_char, c_int};
use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
use std::os::unix::ffi::OsStrExt;
@ -94,7 +95,7 @@ impl Reloader {
}
// Synchronisation pipe:
let (pin, pout) = super::pipe()?;
let (pold, pnew) = super::socketpair()?;
// Start ourselves in the background:
use nix::unistd::{fork, ForkResult};
@ -103,21 +104,31 @@ impl Reloader {
// Double fork so systemd can supervise us without nagging...
match fork() {
Ok(ForkResult::Child) => {
std::mem::drop(pin);
std::mem::drop(pold);
// At this point we call pre-exec helpers. We must be certain that if they fail for
// whatever reason we can still call `_exit()`, so use catch_unwind.
match std::panic::catch_unwind(move || {
let mut pout = unsafe {
std::fs::File::from_raw_fd(pout.into_raw_fd())
let mut pnew = unsafe {
std::fs::File::from_raw_fd(pnew.into_raw_fd())
};
let pid = nix::unistd::Pid::this();
if let Err(e) = unsafe { pout.write_host_value(pid.as_raw()) } {
if let Err(e) = unsafe { pnew.write_host_value(pid.as_raw()) } {
log::error!("failed to send new server PID to parent: {}", e);
unsafe {
libc::_exit(-1);
}
}
std::mem::drop(pout);
let mut ok = [0u8];
if let Err(e) = pnew.read_exact(&mut ok) {
log::error!("parent vanished before notifying systemd: {}", e);
unsafe {
libc::_exit(-1);
}
}
assert_eq!(ok[0], 1, "reload handshake should have sent a 1 byte");
std::mem::drop(pnew);
self.do_reexec(new_args)
})
{
@ -127,7 +138,7 @@ impl Reloader {
}
}
Ok(ForkResult::Parent { child }) => {
std::mem::drop((pin, pout));
std::mem::drop((pold, pnew));
log::debug!("forked off a new server (second pid: {})", child);
}
Err(e) => log::error!("fork() failed, restart delayed: {}", e),
@ -139,11 +150,11 @@ impl Reloader {
}
Ok(ForkResult::Parent { child }) => {
log::debug!("forked off a new server (first pid: {}), waiting for 2nd pid", child);
std::mem::drop(pout);
let mut pin = unsafe {
std::fs::File::from_raw_fd(pin.into_raw_fd())
std::mem::drop(pnew);
let mut pold = unsafe {
std::fs::File::from_raw_fd(pold.into_raw_fd())
};
let child = nix::unistd::Pid::from_raw(match unsafe { pin.read_le_value() } {
let child = nix::unistd::Pid::from_raw(match unsafe { pold.read_le_value() } {
Ok(v) => v,
Err(e) => {
log::error!("failed to receive pid of double-forked child process: {}", e);
@ -155,6 +166,12 @@ impl Reloader {
if let Err(e) = systemd_notify(SystemdNotify::MainPid(child)) {
log::error!("failed to notify systemd about the new main pid: {}", e);
}
// notify child that it is now the new main process:
if let Err(e) = pold.write_all(&[1u8]) {
log::error!("child vanished during reload: {}", e);
}
Ok(())
}
Err(e) => {