Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 500 insertions, 0 deletions

diff --git a/vendor/jobserver/src/lib.rs b/vendor/jobserver/src/lib.rs
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+//! An implementation of the GNU make jobserver.
+//!
+//! This crate is an implementation, in Rust, of the GNU `make` jobserver for
+//! CLI tools that are interoperating with make or otherwise require some form
+//! of parallelism limiting across process boundaries. This was originally
+//! written for usage in Cargo to both (a) work when `cargo` is invoked from
+//! `make` (using `make`'s jobserver) and (b) work when `cargo` invokes build
+//! scripts, exporting a jobserver implementation for `make` processes to
+//! transitively use.
+//!
+//! The jobserver implementation can be found in [detail online][docs] but
+//! basically boils down to a cross-process semaphore. On Unix this is
+//! implemented with the `pipe` syscall and read/write ends of a pipe and on
+//! Windows this is implemented literally with IPC semaphores.
+//!
+//! The jobserver protocol in `make` also dictates when tokens are acquired to
+//! run child work, and clients using this crate should take care to implement
+//! such details to ensure correct interoperation with `make` itself.
+//!
+//! ## Examples
+//!
+//! Connect to a jobserver that was set up by `make` or a different process:
+//!
+//! ```no_run
+//! use jobserver::Client;
+//!
+//! // See API documentation for why this is `unsafe`
+//! let client = match unsafe { Client::from_env() } {
+//!     Some(client) => client,
+//!     None => panic!("client not configured"),
+//! };
+//! ```
+//!
+//! Acquire and release token from a jobserver:
+//!
+//! ```no_run
+//! use jobserver::Client;
+//!
+//! let client = unsafe { Client::from_env().unwrap() };
+//! let token = client.acquire().unwrap(); // blocks until it is available
+//! drop(token); // releases the token when the work is done
+//! ```
+//!
+//! Create a new jobserver and configure a child process to have access:
+//!
+//! ```
+//! use std::process::Command;
+//! use jobserver::Client;
+//!
+//! let client = Client::new(4).expect("failed to create jobserver");
+//! let mut cmd = Command::new("make");
+//! client.configure(&mut cmd);
+//! ```
+//!
+//! ## Caveats
+//!
+//! This crate makes no attempt to release tokens back to a jobserver on
+//! abnormal exit of a process. If a process which acquires a token is killed
+//! with ctrl-c or some similar signal then tokens will not be released and the
+//! jobserver may be in a corrupt state.
+//!
+//! Note that this is typically ok as ctrl-c means that an entire build process
+//! is being torn down, but it's worth being aware of at least!
+//!
+//! ## Windows caveats
+//!
+//! There appear to be two implementations of `make` on Windows. On MSYS2 one
+//! typically comes as `mingw32-make` and the other as `make` itself. I'm not
+//! personally too familiar with what's going on here, but for jobserver-related
+//! information the `mingw32-make` implementation uses Windows semaphores
+//! whereas the `make` program does not. The `make` program appears to use file
+//! descriptors and I'm not really sure how it works, so this crate is not
+//! compatible with `make` on Windows. It is, however, compatible with
+//! `mingw32-make`.
+//!
+//! [docs]: http://make.mad-scientist.net/papers/jobserver-implementation/
+
+#![deny(missing_docs, missing_debug_implementations)]
+#![doc(html_root_url = "https://docs.rs/jobserver/0.1")]
+
+use std::env;
+use std::io;
+use std::process::Command;
+use std::sync::{Arc, Condvar, Mutex, MutexGuard};
+
+#[cfg(unix)]
+#[path = "unix.rs"]
+mod imp;
+#[cfg(windows)]
+#[path = "windows.rs"]
+mod imp;
+#[cfg(not(any(unix, windows)))]
+#[path = "wasm.rs"]
+mod imp;
+
+/// A client of a jobserver
+///
+/// This structure is the main type exposed by this library, and is where
+/// interaction to a jobserver is configured through. Clients are either created
+/// from scratch in which case the internal semphore is initialied on the spot,
+/// or a client is created from the environment to connect to a jobserver
+/// already created.
+///
+/// Some usage examples can be found in the crate documentation for using a
+/// client.
+///
+/// Note that a `Client` implements the `Clone` trait, and all instances of a
+/// `Client` refer to the same jobserver instance.
+#[derive(Clone, Debug)]
+pub struct Client {
+    inner: Arc<imp::Client>,
+}
+
+/// An acquired token from a jobserver.
+///
+/// This token will be released back to the jobserver when it is dropped and
+/// otherwise represents the ability to spawn off another thread of work.
+#[derive(Debug)]
+pub struct Acquired {
+    client: Arc<imp::Client>,
+    data: imp::Acquired,
+    disabled: bool,
+}
+
+impl Acquired {
+    /// This drops the `Acquired` token without releasing the associated token.
+    ///
+    /// This is not generally useful, but can be helpful if you do not have the
+    /// ability to store an Acquired token but need to not yet release it.
+    ///
+    /// You'll typically want to follow this up with a call to `release_raw` or
+    /// similar to actually release the token later on.
+    pub fn drop_without_releasing(mut self) {
+        self.disabled = true;
+    }
+}
+
+#[derive(Default, Debug)]
+struct HelperState {
+    lock: Mutex<HelperInner>,
+    cvar: Condvar,
+}
+
+#[derive(Default, Debug)]
+struct HelperInner {
+    requests: usize,
+    producer_done: bool,
+    consumer_done: bool,
+}
+
+impl Client {
+    /// Creates a new jobserver initialized with the given parallelism limit.
+    ///
+    /// A client to the jobserver created will be returned. This client will
+    /// allow at most `limit` tokens to be acquired from it in parallel. More
+    /// calls to `acquire` will cause the calling thread to block.
+    ///
+    /// Note that the created `Client` is not automatically inherited into
+    /// spawned child processes from this program. Manual usage of the
+    /// `configure` function is required for a child process to have access to a
+    /// job server.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use jobserver::Client;
+    ///
+    /// let client = Client::new(4).expect("failed to create jobserver");
+    /// ```
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if any I/O error happens when attempting to create the
+    /// jobserver client.
+    pub fn new(limit: usize) -> io::Result<Client> {
+        Ok(Client {
+            inner: Arc::new(imp::Client::new(limit)?),
+        })
+    }
+
+    /// Attempts to connect to the jobserver specified in this process's
+    /// environment.
+    ///
+    /// When the a `make` executable calls a child process it will configure the
+    /// environment of the child to ensure that it has handles to the jobserver
+    /// it's passing down. This function will attempt to look for these details
+    /// and connect to the jobserver.
+    ///
+    /// Note that the created `Client` is not automatically inherited into
+    /// spawned child processes from this program. Manual usage of the
+    /// `configure` function is required for a child process to have access to a
+    /// job server.
+    ///
+    /// # Return value
+    ///
+    /// If a jobserver was found in the environment and it looks correct then
+    /// `Some` of the connected client will be returned. If no jobserver was
+    /// found then `None` will be returned.
+    ///
+    /// Note that on Unix the `Client` returned **takes ownership of the file
+    /// descriptors specified in the environment**. Jobservers on Unix are
+    /// implemented with `pipe` file descriptors, and they're inherited from
+    /// parent processes. This `Client` returned takes ownership of the file
+    /// descriptors for this process and will close the file descriptors after
+    /// this value is dropped.
+    ///
+    /// Additionally on Unix this function will configure the file descriptors
+    /// with `CLOEXEC` so they're not automatically inherited by spawned
+    /// children.
+    ///
+    /// # Unsafety
+    ///
+    /// This function is `unsafe` to call on Unix specifically as it
+    /// transitively requires usage of the `from_raw_fd` function, which is
+    /// itself unsafe in some circumstances.
+    ///
+    /// It's recommended to call this function very early in the lifetime of a
+    /// program before any other file descriptors are opened. That way you can
+    /// make sure to take ownership properly of the file descriptors passed
+    /// down, if any.
+    ///
+    /// It's generally unsafe to call this function twice in a program if the
+    /// previous invocation returned `Some`.
+    ///
+    /// Note, though, that on Windows it should be safe to call this function
+    /// any number of times.
+    pub unsafe fn from_env() -> Option<Client> {
+        let var = match env::var("CARGO_MAKEFLAGS")
+            .or_else(|_| env::var("MAKEFLAGS"))
+            .or_else(|_| env::var("MFLAGS"))
+        {
+            Ok(s) => s,
+            Err(_) => return None,
+        };
+        let mut arg = "--jobserver-fds=";
+        let pos = match var.find(arg) {
+            Some(i) => i,
+            None => {
+                arg = "--jobserver-auth=";
+                match var.find(arg) {
+                    Some(i) => i,
+                    None => return None,
+                }
+            }
+        };
+
+        let s = var[pos + arg.len()..].split(' ').next().unwrap();
+        imp::Client::open(s).map(|c| Client { inner: Arc::new(c) })
+    }
+
+    /// Acquires a token from this jobserver client.
+    ///
+    /// This function will block the calling thread until a new token can be
+    /// acquired from the jobserver.
+    ///
+    /// # Return value
+    ///
+    /// On successful acquisition of a token an instance of `Acquired` is
+    /// returned. This structure, when dropped, will release the token back to
+    /// the jobserver. It's recommended to avoid leaking this value.
+    ///
+    /// # Errors
+    ///
+    /// If an I/O error happens while acquiring a token then this function will
+    /// return immediately with the error. If an error is returned then a token
+    /// was not acquired.
+    pub fn acquire(&self) -> io::Result<Acquired> {
+        let data = self.inner.acquire()?;
+        Ok(Acquired {
+            client: self.inner.clone(),
+            data,
+            disabled: false,
+        })
+    }
+
+    /// Configures a child process to have access to this client's jobserver as
+    /// well.
+    ///
+    /// This function is required to be called to ensure that a jobserver is
+    /// properly inherited to a child process. If this function is *not* called
+    /// then this `Client` will not be accessible in the child process. In other
+    /// words, if not called, then `Client::from_env` will return `None` in the
+    /// child process (or the equivalent of `Child::from_env` that `make` uses).
+    ///
+    /// ## Platform-specific behavior
+    ///
+    /// On Unix and Windows this will clobber the `CARGO_MAKEFLAGS` environment
+    /// variables for the child process, and on Unix this will also allow the
+    /// two file descriptors for this client to be inherited to the child.
+    ///
+    /// On platforms other than Unix and Windows this panics.
+    pub fn configure(&self, cmd: &mut Command) {
+        let arg = self.inner.string_arg();
+        // Older implementations of make use `--jobserver-fds` and newer
+        // implementations use `--jobserver-auth`, pass both to try to catch
+        // both implementations.
+        let value = format!("-j --jobserver-fds={0} --jobserver-auth={0}", arg);
+        cmd.env("CARGO_MAKEFLAGS", &value);
+        self.inner.configure(cmd);
+    }
+
+    /// Converts this `Client` into a helper thread to deal with a blocking
+    /// `acquire` function a little more easily.
+    ///
+    /// The fact that the `acquire` function on `Client` blocks isn't always
+    /// the easiest to work with. Typically you're using a jobserver to
+    /// manage running other events in parallel! This means that you need to
+    /// either (a) wait for an existing job to finish or (b) wait for a
+    /// new token to become available.
+    ///
+    /// Unfortunately the blocking in `acquire` happens at the implementation
+    /// layer of jobservers. On Unix this requires a blocking call to `read`
+    /// and on Windows this requires one of the `WaitFor*` functions. Both
+    /// of these situations aren't the easiest to deal with:
+    ///
+    /// * On Unix there's basically only one way to wake up a `read` early, and
+    ///   that's through a signal. This is what the `make` implementation
+    ///   itself uses, relying on `SIGCHLD` to wake up a blocking acquisition
+    ///   of a new job token. Unfortunately nonblocking I/O is not an option
+    ///   here, so it means that "waiting for one of two events" means that
+    ///   the latter event must generate a signal! This is not always the case
+    ///   on unix for all jobservers.
+    ///
+    /// * On Windows you'd have to basically use the `WaitForMultipleObjects`
+    ///   which means that you've got to canonicalize all your event sources
+    ///   into a `HANDLE` which also isn't the easiest thing to do
+    ///   unfortunately.
+    ///
+    /// This function essentially attempts to ease these limitations by
+    /// converting this `Client` into a helper thread spawned into this
+    /// process. The application can then request that the helper thread
+    /// acquires tokens and the provided closure will be invoked for each token
+    /// acquired.
+    ///
+    /// The intention is that this function can be used to translate the event
+    /// of a token acquisition into an arbitrary user-defined event.
+    ///
+    /// # Arguments
+    ///
+    /// This function will consume the `Client` provided to be transferred to
+    /// the helper thread that is spawned. Additionally a closure `f` is
+    /// provided to be invoked whenever a token is acquired.
+    ///
+    /// This closure is only invoked after calls to
+    /// `HelperThread::request_token` have been made and a token itself has
+    /// been acquired. If an error happens while acquiring the token then
+    /// an error will be yielded to the closure as well.
+    ///
+    /// # Return Value
+    ///
+    /// This function will return an instance of the `HelperThread` structure
+    /// which is used to manage the helper thread associated with this client.
+    /// Through the `HelperThread` you'll request that tokens are acquired.
+    /// When acquired, the closure provided here is invoked.
+    ///
+    /// When the `HelperThread` structure is returned it will be gracefully
+    /// torn down, and the calling thread will be blocked until the thread is
+    /// torn down (which should be prompt).
+    ///
+    /// # Errors
+    ///
+    /// This function may fail due to creation of the helper thread or
+    /// auxiliary I/O objects to manage the helper thread. In any of these
+    /// situations the error is propagated upwards.
+    ///
+    /// # Platform-specific behavior
+    ///
+    /// On Windows this function behaves pretty normally as expected, but on
+    /// Unix the implementation is... a little heinous. As mentioned above
+    /// we're forced into blocking I/O for token acquisition, namely a blocking
+    /// call to `read`. We must be able to unblock this, however, to tear down
+    /// the helper thread gracefully!
+    ///
+    /// Essentially what happens is that we'll send a signal to the helper
+    /// thread spawned and rely on `EINTR` being returned to wake up the helper
+    /// thread. This involves installing a global `SIGUSR1` handler that does
+    /// nothing along with sending signals to that thread. This may cause
+    /// odd behavior in some applications, so it's recommended to review and
+    /// test thoroughly before using this.
+    pub fn into_helper_thread<F>(self, f: F) -> io::Result<HelperThread>
+    where
+        F: FnMut(io::Result<Acquired>) + Send + 'static,
+    {
+        let state = Arc::new(HelperState::default());
+        Ok(HelperThread {
+            inner: Some(imp::spawn_helper(self, state.clone(), Box::new(f))?),
+            state,
+        })
+    }
+
+    /// Blocks the current thread until a token is acquired.
+    ///
+    /// This is the same as `acquire`, except that it doesn't return an RAII
+    /// helper. If successful the process will need to guarantee that
+    /// `release_raw` is called in the future.
+    pub fn acquire_raw(&self) -> io::Result<()> {
+        self.inner.acquire()?;
+        Ok(())
+    }
+
+    /// Releases a jobserver token back to the original jobserver.
+    ///
+    /// This is intended to be paired with `acquire_raw` if it was called, but
+    /// in some situations it could also be called to relinquish a process's
+    /// implicit token temporarily which is then re-acquired later.
+    pub fn release_raw(&self) -> io::Result<()> {
+        self.inner.release(None)?;
+        Ok(())
+    }
+}
+
+impl Drop for Acquired {
+    fn drop(&mut self) {
+        if !self.disabled {
+            drop(self.client.release(Some(&self.data)));
+        }
+    }
+}
+
+/// Structure returned from `Client::into_helper_thread` to manage the lifetime
+/// of the helper thread returned, see those associated docs for more info.
+#[derive(Debug)]
+pub struct HelperThread {
+    inner: Option<imp::Helper>,
+    state: Arc<HelperState>,
+}
+
+impl HelperThread {
+    /// Request that the helper thread acquires a token, eventually calling the
+    /// original closure with a token when it's available.
+    ///
+    /// For more information, see the docs on that function.
+    pub fn request_token(&self) {
+        // Indicate that there's one more request for a token and then wake up
+        // the helper thread if it's sleeping.
+        self.state.lock().requests += 1;
+        self.state.cvar.notify_one();
+    }
+}
+
+impl Drop for HelperThread {
+    fn drop(&mut self) {
+        // Flag that the producer half is done so the helper thread should exit
+        // quickly if it's waiting. Wake it up if it's actually waiting
+        self.state.lock().producer_done = true;
+        self.state.cvar.notify_one();
+
+        // ... and afterwards perform any thread cleanup logic
+        self.inner.take().unwrap().join();
+    }
+}
+
+impl HelperState {
+    fn lock(&self) -> MutexGuard<'_, HelperInner> {
+        self.lock.lock().unwrap_or_else(|e| e.into_inner())
+    }
+
+    /// Executes `f` for each request for a token, where `f` is expected to
+    /// block and then provide the original closure with a token once it's
+    /// acquired.
+    ///
+    /// This is an infinite loop until the helper thread is dropped, at which
+    /// point everything should get interrupted.
+    fn for_each_request(&self, mut f: impl FnMut(&HelperState)) {
+        let mut lock = self.lock();
+
+        // We only execute while we could receive requests, but as soon as
+        // that's `false` we're out of here.
+        while !lock.producer_done {
+            // If no one's requested a token then we wait for someone to
+            // request a token.
+            if lock.requests == 0 {
+                lock = self.cvar.wait(lock).unwrap_or_else(|e| e.into_inner());
+                continue;
+            }
+
+            // Consume the request for a token, and then actually acquire a
+            // token after unlocking our lock (not that acquisition happens in
+            // `f`). This ensures that we don't actually hold the lock if we
+            // wait for a long time for a token.
+            lock.requests -= 1;
+            drop(lock);
+            f(self);
+            lock = self.lock();
+        }
+        lock.consumer_done = true;
+        self.cvar.notify_one();
+    }
+
+    fn producer_done(&self) -> bool {
+        self.lock().producer_done
+    }
+}
+
+#[test]
+fn no_helper_deadlock() {
+    let x = crate::Client::new(32).unwrap();
+    let _y = x.clone();
+    std::mem::drop(x.into_helper_thread(|_| {}).unwrap());
+}