Fix Client::configure* on unix

src/lib.rs

@@ -644,7 +644,7 @@ mod test {
         client.try_acquire().unwrap().unwrap();
     }
 
-    #[cfg(not(unix))]
+    #[cfg(windows)]
     #[test]
     fn test_try_acquire() {
         let client = Client::new(0).unwrap();

src/unix.rs

@@ -6,7 +6,7 @@ use std::io::{self, Read, Write};
 use std::mem;
 use std::mem::MaybeUninit;
 use std::os::unix::prelude::*;
-use std::path::{Path, PathBuf};
+use std::path::Path;
 use std::process::Command;
 use std::ptr;
 use std::sync::{
@@ -17,17 +17,27 @@ use std::thread::{self, Builder, JoinHandle};
 use std::time::Duration;
 
 #[derive(Debug)]
-pub enum Client {
-    /// `--jobserver-auth=R,W`
-    Pipe { read: File, write: File },
-    /// `--jobserver-auth=fifo:PATH`
-    Fifo {
-        file: File,
-        path: PathBuf,
-        /// it can only go from false -> true but not the other way around, since that
-        ///  could cause a race condition.
-        is_non_blocking: AtomicBool,
-    },
+/// This preserves the `--jobserver-auth` type at creation time,
+/// so auth type will be passed down to and inherit from sub-Make processes correctly.
+///
+/// See <https://github.com/rust-lang/jobserver-rs/issues/99> for details.
+enum ClientCreationArg {
+    Fds { read: c_int, write: c_int },
+    Fifo(Box<Path>),
+}
+
+#[derive(Debug)]
+pub struct Client {
+    read: File,
+    write: File,
+    creation_arg: ClientCreationArg,
+    /// It is set to `None` if the pipe is shared with other processes, so it
+    /// cannot support non-blocking mode.
+    ///
+    /// If it is set to `Some`, then it can only go from
+    /// `Some(false)` -> `Some(true)` but not the other way around,
+    /// since that could cause a race condition.
+    is_non_blocking: Option<AtomicBool>,
 }
 
 #[derive(Debug)]
@@ -43,7 +53,7 @@ impl Client {
         // wrong!
         const BUFFER: [u8; 128] = [b'|'; 128];
 
-        let mut write = client.write();
+        let mut write = &client.write;
 
         set_nonblocking(write.as_raw_fd(), true)?;
 
@@ -111,16 +121,24 @@ impl Client {
             FromEnvErrorInner::CannotParse("expected a path after `fifo:`".to_string())
         })?;
         let path = Path::new(path_str);
-        let file = OpenOptions::new()
-            .read(true)
-            .write(true)
-            .open(path)
-            .map_err(|err| FromEnvErrorInner::CannotOpenPath(path_str.to_string(), err))?;
-
-        Ok(Some(Client::Fifo {
-            file,
-            path: path.into(),
-            is_non_blocking: AtomicBool::new(false),
+
+        let open_file = || {
+            // Opening with read write is necessary, since opening with
+            // read-only or write-only could block the thread until another
+            // thread opens it with write-only or read-only (or RDWR)
+            // correspondingly.
+            OpenOptions::new()
+                .read(true)
+                .write(true)
+                .open(path)
+                .map_err(|err| FromEnvErrorInner::CannotOpenPath(path_str.to_string(), err))
+        };
+
+        Ok(Some(Client {
+            read: open_file()?,
+            write: open_file()?,
+            creation_arg: ClientCreationArg::Fifo(path.into()),
+            is_non_blocking: Some(AtomicBool::new(false)),
         }))
     }
 
@@ -148,6 +166,8 @@ impl Client {
             return Err(FromEnvErrorInner::NegativeFd(write));
         }
 
+        let creation_arg = ClientCreationArg::Fds { read, write };
+
         // Ok so we've got two integers that look like file descriptors, but
         // for extra sanity checking let's see if they actually look like
         // valid files and instances of a pipe if feature enabled before we
@@ -174,40 +194,36 @@ impl Client {
                 //
                 // I tested this on macOS 14 and Linux 6.5.13
                 #[cfg(target_os = "linux")]
-                if let Ok(Some(jobserver)) =
-                    Self::from_fifo(&format!("fifo:/dev/fd/{}", read.as_raw_fd()))
-                {
-                    return Ok(Some(jobserver));
+                if let (Ok(read), Ok(write)) = (
+                    File::open(format!("/dev/fd/{}", read)),
+                    OpenOptions::new()
+                        .write(true)
+                        .open(format!("/dev/fd/{}", write)),
+                ) {
+                    return Ok(Some(Client {
+                        read,
+                        write,
+                        creation_arg,
+                        is_non_blocking: Some(AtomicBool::new(false)),
+                    }));
                 }
             }
         }
 
-        Ok(Some(Client::Pipe {
+        Ok(Some(Client {
             read: clone_fd_and_set_cloexec(read)?,
             write: clone_fd_and_set_cloexec(write)?,
+            creation_arg,
+            is_non_blocking: None,
         }))
     }
 
     unsafe fn from_fds(read: c_int, write: c_int) -> Client {
-        Client::Pipe {
+        Client {
             read: File::from_raw_fd(read),
             write: File::from_raw_fd(write),
-        }
-    }
-
-    /// Gets the read end of our jobserver client.
-    fn read(&self) -> &File {
-        match self {
-            Client::Pipe { read, .. } => read,
-            Client::Fifo { file, .. } => file,
-        }
-    }
-
-    /// Gets the write end of our jobserver client.
-    fn write(&self) -> &File {
-        match self {
-            Client::Pipe { write, .. } => write,
-            Client::Fifo { file, .. } => file,
+            creation_arg: ClientCreationArg::Fds { read, write },
+            is_non_blocking: None,
         }
     }
 
@@ -245,7 +261,7 @@ impl Client {
         // to shut us down, so we otherwise punt all errors upwards.
         unsafe {
             let mut fd: libc::pollfd = mem::zeroed();
-            let mut read = self.read();
+            let mut read = &self.read;
             fd.fd = read.as_raw_fd();
             fd.events = libc::POLLIN;
             loop {
@@ -284,19 +300,15 @@ impl Client {
 
     pub fn try_acquire(&self) -> io::Result<Option<Acquired>> {
         let mut buf = [0];
+        let mut fifo = &self.read;
 
-        let (mut fifo, is_non_blocking) = match self {
-            Self::Fifo {
-                file,
-                is_non_blocking,
-                ..
-            } => (file, is_non_blocking),
-            _ => return Err(io::ErrorKind::Unsupported.into()),
-        };
-
-        if !is_non_blocking.load(Ordering::Relaxed) {
-            set_nonblocking(fifo.as_raw_fd(), true)?;
-            is_non_blocking.store(true, Ordering::Relaxed);
+        if let Some(is_non_blocking) = self.is_non_blocking.as_ref() {
+            if !is_non_blocking.load(Ordering::Relaxed) {
+                set_nonblocking(fifo.as_raw_fd(), true)?;
+                is_non_blocking.store(true, Ordering::Relaxed);
+            }
+        } else {
+            return Err(io::ErrorKind::Unsupported.into());
         }
 
         loop {
@@ -323,7 +335,7 @@ impl Client {
         // always quickly release a token). If that turns out to not be the
         // case we'll get an error anyway!
         let byte = data.map(|d| d.byte).unwrap_or(b'+');
-        match self.write().write(&[byte])? {
+        match (&self.write).write(&[byte])? {
             1 => Ok(()),
             _ => Err(io::Error::new(
                 io::ErrorKind::Other,
@@ -333,31 +345,30 @@ impl Client {
     }
 
     pub fn string_arg(&self) -> String {
-        match self {
-            Client::Pipe { read, write } => format!("{},{}", read.as_raw_fd(), write.as_raw_fd()),
-            Client::Fifo { path, .. } => format!("fifo:{}", path.to_str().unwrap()),
+        match &self.creation_arg {
+            ClientCreationArg::Fifo(path) => format!("fifo:{}", path.display()),
+            ClientCreationArg::Fds { read, write } => format!("{},{}", read, write),
         }
     }
 
     pub fn available(&self) -> io::Result<usize> {
         let mut len = MaybeUninit::<c_int>::uninit();
-        cvt(unsafe { libc::ioctl(self.read().as_raw_fd(), libc::FIONREAD, len.as_mut_ptr()) })?;
+        cvt(unsafe { libc::ioctl(self.read.as_raw_fd(), libc::FIONREAD, len.as_mut_ptr()) })?;
         Ok(unsafe { len.assume_init() } as usize)
     }
 
     pub fn configure(&self, cmd: &mut Command) {
-        match self {
+        if matches!(self.creation_arg, ClientCreationArg::Fifo { .. }) {
             // We `File::open`ed it when inheriting from environment,
             // so no need to set cloexec for fifo.
-            Client::Fifo { .. } => return,
-            Client::Pipe { .. } => {}
-        };
+            return;
+        }
         // Here we basically just want to say that in the child process
         // we'll configure the read/write file descriptors to *not* be
         // cloexec, so they're inherited across the exec and specified as
         // integers through `string_arg` above.
-        let read = self.read().as_raw_fd();
-        let write = self.write().as_raw_fd();
+        let read = self.read.as_raw_fd();
+        let write = self.write.as_raw_fd();
         unsafe {
             cmd.pre_exec(move || {
                 set_cloexec(read, false)?;
@@ -559,55 +570,82 @@ mod test {
 
     use crate::{test::run_named_fifo_try_acquire_tests, Client};
 
-    use std::sync::Arc;
+    use std::{
+        fs::File,
+        io::{self, Write},
+        os::unix::io::AsRawFd,
+        sync::Arc,
+    };
 
     fn from_imp_client(imp: ClientImp) -> Client {
         Client {
             inner: Arc::new(imp),
         }
     }
 
-    #[test]
-    fn test_try_acquire_named_fifo() {
+    fn new_client_from_fifo() -> (Client, String) {
         let file = tempfile::NamedTempFile::new().unwrap();
         let fifo_path = file.path().to_owned();
         file.close().unwrap(); // Remove the NamedTempFile to create fifo
 
         nix::unistd::mkfifo(&fifo_path, nix::sys::stat::Mode::S_IRWXU).unwrap();
 
-        let client = ClientImp::from_fifo(&format!("fifo:{}", fifo_path.to_str().unwrap()))
-            .unwrap()
-            .map(from_imp_client)
-            .unwrap();
+        let arg = format!("fifo:{}", fifo_path.to_str().unwrap());
 
-        run_named_fifo_try_acquire_tests(&client);
+        (
+            ClientImp::from_fifo(&arg)
+                .unwrap()
+                .map(from_imp_client)
+                .unwrap(),
+            arg,
+        )
     }
 
-    #[cfg(not(target_os = "linux"))]
-    #[test]
-    fn test_try_acquire_annoymous_pipe_linux_specific_optimization() {
-        use std::{
-            fs::File,
-            io::{self, Write},
-            os::unix::io::AsRawFd,
-        };
-
+    fn new_client_from_pipe() -> (Client, String) {
         let (read, write) = nix::unistd::pipe().unwrap();
         let read = File::from(read);
         let mut write = File::from(write);
 
         write.write_all(b"1").unwrap();
 
-        let client = unsafe {
-            ClientImp::from_pipe(&format!("{},{}", read.as_raw_fd(), write.as_raw_fd()), true)
-        }
-        .unwrap()
-        .map(from_imp_client)
-        .unwrap();
+        let arg = format!("{},{}", read.as_raw_fd(), write.as_raw_fd());
+
+        (
+            unsafe { ClientImp::from_pipe(&arg, true) }
+                .unwrap()
+                .map(from_imp_client)
+                .unwrap(),
+            arg,
+        )
+    }
 
+    #[test]
+    fn test_try_acquire_named_fifo() {
+        run_named_fifo_try_acquire_tests(&new_client_from_fifo().0);
+    }
+
+    #[test]
+    fn test_try_acquire_annoymous_pipe_linux_specific_optimization() {
+        #[cfg(not(target_os = "linux"))]
         assert_eq!(
-            client.try_acquire().unwrap_err().kind(),
+            new_client_from_pipe().0.try_acquire().unwrap_err().kind(),
             io::ErrorKind::Unsupported
         );
+
+        #[cfg(target_os = "linux")]
+        {
+            let client = new_client_from_pipe().0;
+            client.acquire().unwrap().drop_without_releasing();
+            run_named_fifo_try_acquire_tests(&client);
+        }
+    }
+
+    #[test]
+    fn test_string_arg() {
+        let (client, arg) = new_client_from_fifo();
+        assert_eq!(client.inner.string_arg(), arg);
+
+        let (client, arg) = new_client_from_pipe();
+        assert_eq!(client.inner.string_arg(), arg);
     }
 }