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Remove return value from pause #829

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Remove return value from pause #829

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2 changes: 2 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -50,6 +50,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
([#741](https://github.com/nix-rust/nix/pull/741))
- Added more standard trait implementations for various types.
([#814](https://github.com/nix-rust/nix/pull/814))
- Remove return type from `pause`.
([#829](https://github.com/nix-rust/nix/pull/829))

### Changed
- Use native `pipe2` on all BSD targets. Users should notice no difference.
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10 changes: 4 additions & 6 deletions src/unistd.rs
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Expand Up @@ -1316,14 +1316,12 @@ pub fn initgroups(user: &CStr, group: Gid) -> Result<()> {
Errno::result(res).map(|_| ())
}

/// Suspend the thread until a signal is received
/// Suspend the thread until a signal is received.
///
/// See also [pause(2)](http://pubs.opengroup.org/onlinepubs/9699919799/functions/pause.html)
/// See also [pause(2)](http://pubs.opengroup.org/onlinepubs/9699919799/functions/pause.html).
#[inline]
pub fn pause() -> Result<()> {
let res = unsafe { libc::pause() };

Errno::result(res).map(drop)
pub fn pause() {
unsafe { libc::pause() };
}

/// Suspend execution for an interval of time
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2 changes: 1 addition & 1 deletion test/sys/test_wait.rs
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Expand Up @@ -12,7 +12,7 @@ fn test_wait_signal() {

// Safe: The child only calls `pause` and/or `_exit`, which are async-signal-safe.
match fork().expect("Error: Fork Failed") {
Child => pause().unwrap_or_else(|_| unsafe { _exit(123) }),
Child => pause(),
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I believe that you have to call _exit() instead of letting the thread naturally exit because of how Rust's standard cleanup isn't signal safe or something. @asomers Can you verify this?

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Yep. The standard cleanup may try to access shared resources that were exclusively held by other threads at the time that fork happened. But those other threads don't exist in the child, so your thread will never get the resources, and deadlock will result. That's why we call _exit in child threads.

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Maybe I'm misunderstanding something but, isn't unwrap_or_else only called if pause fails and returns an error. Since that can't happend anymore _exit can never be called, and would have never be called even without the change.

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I've fixed this in #836, for some reason this pull request is now "from unknown repository". I don't know how to fix that, so instead I created an new pr.

Parent { child } => {
kill(child, Some(SIGKILL)).expect("Error: Kill Failed");
assert_eq!(waitpid(child, None), Ok(WaitStatus::Signaled(child, SIGKILL, false)));
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