Init: Graceful termination and signal propagation #29

rawan · 2026-03-10T22:02:16Z

rawan commented

2026-03-10 22:02:16 +00:00

related issue: #8

Changes implemented:

Re-entrancy guard on poweroff
Added AtomicBool flag. The first thread to call poweroff() claims it. Any subsequent callers loop on pause() forever, preventing concurrent shutdown races on unmounts and the reboot syscall.
Child process termination before unmounting
Added terminate_all_children() which runs before sync() and unmounts:
- Sends SIGTERM to all child processes
- Polls for up to 3 seconds, reaping exited children every 50ms
- If any children survive, sends SIGKILL and reaps for up to 1 second

This ensures all file handles on mounts are released before umount runs

related issue: https://forge.ourworld.tf/geomind_code/my_hypervisor/issues/8 Changes implemented: 1. Re-entrancy guard on `poweroff` Added AtomicBool flag. The first thread to call poweroff() claims it. Any subsequent callers loop on pause() forever, preventing concurrent shutdown races on unmounts and the reboot syscall. 2. Child process termination before unmounting Added `terminate_all_children()` which runs before sync() and unmounts: - Sends SIGTERM to all child processes - Polls for up to 3 seconds, reaping exited children every 50ms - If any children survive, sends SIGKILL and reaps for up to 1 second This ensures all file handles on mounts are released before umount runs

rawan added 1 commit

2026-03-10 22:02:16 +00:00

feat: child termination before unmount, re-entrancy guard on poweroff

Unit and Integration Test / test (push) Successful in 1m47s

Details

5ea2d78324

rawan requested review from salmaelsoly

2026-03-10 22:02:34 +00:00

salmaelsoly requested changes

2026-03-11 14:18:09 +00:00

Dismissed

crates/chvm-init/src/signal.rs Outdated

					
				@ -25,1 +31,4 @@

				/// Non-blocking reap of all zombie children.

				fn reap_all_children() {

				    loop {

i think this is normal blocking function can u update the comment because it's kinda confusing

it is non-blocking due to the WNOHANG flag, the loop keeps reaping any exited children and breaks as soon as there are none left to collect, so the function never stalls waiting for a child that's still running

it is non-blocking due to the `WNOHANG` flag, the loop keeps reaping any exited children and breaks as soon as there are none left to collect, so the function never stalls waiting for a child that's still running

I meant that u should wait for the function to return or to break

crates/chvm-init/src/signal.rs Outdated

					
				@ -26,0 +41,4 @@

				            }

				            Ok(WaitStatus::StillAlive) | Err(_) => break,

				            _ => continue,

				        }

why we are breaking on still alive shouldn't we continue?

Still alive means there's no more zombies to collect right now. All living children are still running so we should break(no reaping work to do)

actually this is an infinite loop, so we should break somewhere to avoid running forever

Still alive means there's no more zombies to collect right now. All living children are still running so we should break(no reaping work to do) actually this is an infinite loop, so we should break somewhere to avoid running forever

👍 1

crates/chvm-init/src/signal.rs Outdated

					
				@ -26,0 +59,4 @@

				    while Instant::now() < deadline {

				        reap_all_children();

				        if no_children_left() {

				            return;

why we still need this check? already reap all children match on waitpid and returns so the status of children can be known from it i think no_children_left is just redundant

we can adjust reap all children to return bool and remove no_children_left

rawan marked this conversation as resolved

crates/chvm-init/src/signal.rs Outdated

					
				@ -26,0 +66,4 @@

				    println!("[init] Sending SIGKILL to remaining child processes...");

				    let _ = nix::sys::signal::kill(Pid::from_raw(-1), Signal::SIGKILL);

this signal all process does it exclude the calling process itself?

yes, kill with pid -1 is sent to every process for which the calling process has permission to send signals, except for process 1 (init), which is the calling process

see kill(2) man page man 2 kill

yes, kill with pid -1 is sent to every process for which the calling process has permission to send signals, except for process 1 (init), which is the calling process see kill(2) man page `man 2 kill`

👍 1

crates/chvm-init/src/signal.rs Outdated

					
				@ -26,0 +74,4 @@

				            return;

				        }

				        std::thread::sleep(Duration::from_millis(50));

				    }

this part is duplicated we can extract it into helper function with setting delay needed

 fn wait_for_children(timeout: Duration) -> bool {
      let deadline = Instant::now() + timeout;
      while Instant::now() < deadline {
          reap_all_children() 
          if no_children_left{ 
              return true;
          }
          std::thread::sleep(Duration::from_millis(50));
      }
      false
  }

this part is duplicated we can extract it into helper function with setting delay needed ``` fn wait_for_children(timeout: Duration) -> bool { let deadline = Instant::now() + timeout; while Instant::now() < deadline { reap_all_children() if no_children_left{ return true; } std::thread::sleep(Duration::from_millis(50)); } false } ```

rawan marked this conversation as resolved

rawan added 1 commit

2026-03-12 00:15:30 +00:00

refactor: remove cope duplication, adding constants

Unit and Integration Test / test (push) Successful in 1m46s

Details

ee45cd3ec9

rawan requested review from salmaelsoly

2026-03-12 00:15:33 +00:00

salmaelsoly commented

2026-03-12 07:52:36 +00:00

can u please fix conflicts