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crosvm: clean up waiting for children

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Signed-off-by: Stephen Barber <smbarber@chromium.org>

BUG=none
TEST=run and kill block device process

Change-Id: I1a4e98cb1985bfeb2303428f95f3bae27dccf803
Reviewed-on: https://chromium-review.googlesource.com/576463
Commit-Ready: Stephen Barber <smbarber@chromium.org>
Tested-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
This commit is contained in:
Stephen Barber 2017-07-18 13:57:26 -07:00 committed by chrome-bot
parent 56fbf09eac
commit a00753ba37
1 changed files with 42 additions and 30 deletions
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72
src/main.rs
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@ -143,6 +143,47 @@ fn create_base_minijail(root: &Path, seccomp_policy: &Path) -> Result<Minijail>
Ok(j)
}
// Wait for all children to exit. Return true if they have all exited, false
// otherwise.
fn wait_all_children() -> bool {
const CHILD_WAIT_MAX_ITER: isize = 10;
const CHILD_WAIT_MS: u64 = 10;
for _ in 0..CHILD_WAIT_MAX_ITER {
// waitpid() is safe when used in this manner; we will check
// without blocking if there are any child processes that
// are still running or need their exit statuses reaped.
loop {
let ret = unsafe {
libc::waitpid(-1, ptr::null_mut(), libc::WNOHANG)
};
// waitpid() returns -1 when there are no children left, and
// returns 0 when there are children alive but not yet exited.
if ret < 0 {
let err = sys_util::Error::last().errno();
// We expect ECHILD which indicates that there were
// no children left.
if err == libc::ECHILD {
return true;
}
else {
warn!("waitpid returned {} while waiting for children",
err);
}
return false;
} else if ret == 0 {
break;
}
}
// There's no timeout option for waitpid, so our only recourse
// is to use WNOHANG and sleep while waiting for the children
// to exit.
sleep(Duration::from_millis(CHILD_WAIT_MS));
}
// If we've made it to this point, not all of the children have exited.
return false;
}
fn run_config(cfg: Config) -> Result<()> {
let socket = if let Some(ref socket_path) = cfg.socket_path {
Some(ControlSocketRecv::new(socket_path)
@ -596,36 +637,7 @@ fn main() {
// all devices should have been dropped in the main process and
// told to shutdown. Try over a period of 100ms, since it may
// take some time for the processes to shut down.
let mut all_children_exited: bool = false;
const CHILD_WAIT_MAX_ITER: isize = 10;
const CHILD_WAIT_MS: u64 = 10;
for _ in 0..CHILD_WAIT_MAX_ITER {
// waitpid() is safe when used in this manner; we will check
// without blocking if there are any child processes that
// are still running or need their exit statuses reaped.
let ret = unsafe {
libc::waitpid(-1, ptr::null_mut(), libc::WNOHANG)
};
// waitpid() returns -1 when there are no children left.
if ret < 0 {
let err = sys_util::Error::last().errno();
// We expect ECHILD which indicates that there were
// no children left.
if err == libc::ECHILD {
all_children_exited = true;
}
else {
warn!("waitpid returned {} while waiting for children",
err);
}
break;
}
// There's no timeout option for waitpid, so our only recourse
// is to use WNOHANG and sleep while waiting for the children
// to exit.
sleep(Duration::from_millis(CHILD_WAIT_MS));
}
if !all_children_exited {
if !wait_all_children() {
// We gave them a chance, and it's too late.
// A pid of 0 will kill any processes left in our process group,
// which is safe for us to do (we spawned them).