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Auto merge of rust-lang#124101 - the8472:pidfd-methods, r=cuviper
Add PidFd::{kill, wait, try_wait}
rust-lang#117957 changed `Child` kill/wait/try_wait to use its pidfd instead of the pid, when one is available.
This PR extracts those implementations and makes them available on `PidFd` directly.
The `PidFd` implementations differ significantly from the corresponding `Child` methods:
* the methods can be called after the child has been reaped, which will result in an error but will be safe. This state is not observable in `Child` unless something stole the zombie child
* the `ExitStatus` is not kept, meaning that only the first time a wait succeeds it will be returned
* `wait` does not close stdin
* `wait` only requires `&self` instead of `&mut self` since there is no state to maintain and subsequent calls are safe
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 1 @@ | ||
| pub mod pidfd; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 1,76 @@ | ||
| use crate::io; | ||
| use crate::os::fd::{AsRawFd, FromRawFd, RawFd}; | ||
| use crate::sys::cvt; | ||
| use crate::sys::pal::unix::fd::FileDesc; | ||
| use crate::sys::process::ExitStatus; | ||
| use crate::sys_common::{AsInner, FromInner, IntoInner}; | ||
|
|
||
| #[cfg(test)] | ||
| mod tests; | ||
|
|
||
| #[derive(Debug)] | ||
| pub(crate) struct PidFd(FileDesc); | ||
|
|
||
| impl PidFd { | ||
| pub fn kill(&self) -> io::Result<()> { | ||
| return cvt(unsafe { | ||
| libc::syscall( | ||
| libc::SYS_pidfd_send_signal, | ||
| self.0.as_raw_fd(), | ||
| libc::SIGKILL, | ||
| crate::ptr::null::<()>(), | ||
| 0, | ||
| ) | ||
| }) | ||
| .map(drop); | ||
| } | ||
|
|
||
| pub fn wait(&self) -> io::Result<ExitStatus> { | ||
| let mut siginfo: libc::siginfo_t = unsafe { crate::mem::zeroed() }; | ||
| cvt(unsafe { | ||
| libc::waitid(libc::P_PIDFD, self.0.as_raw_fd() as u32, &mut siginfo, libc::WEXITED) | ||
| })?; | ||
| return Ok(ExitStatus::from_waitid_siginfo(siginfo)); | ||
| } | ||
|
|
||
| pub fn try_wait(&self) -> io::Result<Option<ExitStatus>> { | ||
| let mut siginfo: libc::siginfo_t = unsafe { crate::mem::zeroed() }; | ||
|
|
||
| cvt(unsafe { | ||
| libc::waitid( | ||
| libc::P_PIDFD, | ||
| self.0.as_raw_fd() as u32, | ||
| &mut siginfo, | ||
| libc::WEXITED | libc::WNOHANG, | ||
| ) | ||
| })?; | ||
| if unsafe { siginfo.si_pid() } == 0 { | ||
| return Ok(None); | ||
| } | ||
| return Ok(Some(ExitStatus::from_waitid_siginfo(siginfo))); | ||
| } | ||
| } | ||
|
|
||
| impl AsInner<FileDesc> for PidFd { | ||
| fn as_inner(&self) -> &FileDesc { | ||
| &self.0 | ||
| } | ||
| } | ||
|
|
||
| impl IntoInner<FileDesc> for PidFd { | ||
| fn into_inner(self) -> FileDesc { | ||
| self.0 | ||
| } | ||
| } | ||
|
|
||
| impl FromInner<FileDesc> for PidFd { | ||
| fn from_inner(inner: FileDesc) -> Self { | ||
| Self(inner) | ||
| } | ||
| } | ||
|
|
||
| impl FromRawFd for PidFd { | ||
| unsafe fn from_raw_fd(fd: RawFd) -> Self { | ||
| Self(FileDesc::from_raw_fd(fd)) | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 1,87 @@ | ||
| use crate::assert_matches::assert_matches; | ||
| use crate::os::fd::{AsRawFd, RawFd}; | ||
| use crate::os::linux::process::{ChildExt, CommandExt}; | ||
| use crate::os::unix::process::ExitStatusExt; | ||
| use crate::process::Command; | ||
|
|
||
| #[test] | ||
| fn test_command_pidfd() { | ||
| let pidfd_open_available = probe_pidfd_support(); | ||
|
|
||
| // always exercise creation attempts | ||
| let mut child = Command::new("false").create_pidfd(true).spawn().unwrap(); | ||
|
|
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| // but only check if we know that the kernel supports pidfds. | ||
| // We don't assert the precise value, since the standard library | ||
| // might have opened other file descriptors before our code runs. | ||
| if pidfd_open_available { | ||
| assert!(child.pidfd().is_ok()); | ||
| } | ||
| if let Ok(pidfd) = child.pidfd() { | ||
| let flags = super::cvt(unsafe { libc::fcntl(pidfd.as_raw_fd(), libc::F_GETFD) }).unwrap(); | ||
| assert!(flags & libc::FD_CLOEXEC != 0); | ||
| } | ||
| let status = child.wait().expect("error waiting on pidfd"); | ||
| assert_eq!(status.code(), Some(1)); | ||
|
|
||
| let mut child = Command::new("sleep").arg("1000").create_pidfd(true).spawn().unwrap(); | ||
| assert_matches!(child.try_wait(), Ok(None)); | ||
| child.kill().expect("failed to kill child"); | ||
| let status = child.wait().expect("error waiting on pidfd"); | ||
| assert_eq!(status.signal(), Some(libc::SIGKILL)); | ||
|
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||
| let _ = Command::new("echo") | ||
| .create_pidfd(false) | ||
| .spawn() | ||
| .unwrap() | ||
| .pidfd() | ||
| .expect_err("pidfd should not have been created when create_pid(false) is set"); | ||
|
|
||
| let _ = Command::new("echo") | ||
| .spawn() | ||
| .unwrap() | ||
| .pidfd() | ||
| .expect_err("pidfd should not have been created"); | ||
| } | ||
|
|
||
| #[test] | ||
| fn test_pidfd() { | ||
| if !probe_pidfd_support() { | ||
| return; | ||
| } | ||
|
|
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| let child = Command::new("sleep") | ||
| .arg("1000") | ||
| .create_pidfd(true) | ||
| .spawn() | ||
| .expect("executing 'sleep' failed"); | ||
|
|
||
| let fd = child.into_pidfd().unwrap(); | ||
|
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| assert_matches!(fd.try_wait(), Ok(None)); | ||
| fd.kill().expect("kill failed"); | ||
| fd.kill().expect("sending kill twice failed"); | ||
| let status = fd.wait().expect("1st wait failed"); | ||
| assert_eq!(status.signal(), Some(libc::SIGKILL)); | ||
|
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| // Trying to wait again for a reaped child is safe since there's no pid-recycling race. | ||
| // But doing so will return an error. | ||
| let res = fd.wait(); | ||
| assert_matches!(res, Err(e) if e.raw_os_error() == Some(libc::ECHILD)); | ||
|
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| // Ditto for additional attempts to kill an already-dead child. | ||
| let res = fd.kill(); | ||
| assert_matches!(res, Err(e) if e.raw_os_error() == Some(libc::ESRCH)); | ||
| } | ||
|
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| fn probe_pidfd_support() -> bool { | ||
| // pidfds require the pidfd_open syscall | ||
| let our_pid = crate::process::id(); | ||
| let pidfd = unsafe { libc::syscall(libc::SYS_pidfd_open, our_pid, 0) }; | ||
| if pidfd >= 0 { | ||
| unsafe { libc::close(pidfd as RawFd) }; | ||
| true | ||
| } else { | ||
| false | ||
| } | ||
| } |
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