diff options
Diffstat (limited to 'library/std/src/thread/mod.rs')
| -rw-r--r-- | library/std/src/thread/mod.rs | 162 |
1 files changed, 64 insertions, 98 deletions
diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs index a53e3565dfe..d1d4eabb9bd 100644 --- a/library/std/src/thread/mod.rs +++ b/library/std/src/thread/mod.rs @@ -141,7 +141,7 @@ //! [`Result`]: crate::result::Result //! [`Ok`]: crate::result::Result::Ok //! [`Err`]: crate::result::Result::Err -//! [`thread::current`]: current +//! [`thread::current`]: current::current //! [`thread::Result`]: Result //! [`unpark`]: Thread::unpark //! [`thread::park_timeout`]: park_timeout @@ -155,17 +155,16 @@ // Under `test`, `__FastLocalKeyInner` seems unused. #![cfg_attr(test, allow(dead_code))] -#[cfg(all(test, not(target_os = "emscripten")))] +#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))] mod tests; use crate::any::Any; -use crate::cell::{Cell, OnceCell, UnsafeCell}; +use crate::cell::UnsafeCell; use crate::ffi::CStr; use crate::marker::PhantomData; use crate::mem::{self, ManuallyDrop, forget}; use crate::num::NonZero; use crate::pin::Pin; -use crate::ptr::addr_of_mut; use crate::sync::Arc; use crate::sync::atomic::{AtomicUsize, Ordering}; use crate::sys::sync::Parker; @@ -180,6 +179,12 @@ mod scoped; #[stable(feature = "scoped_threads", since = "1.63.0")] pub use scoped::{Scope, ScopedJoinHandle, scope}; +mod current; + +#[stable(feature = "rust1", since = "1.0.0")] +pub use current::current; +pub(crate) use current::{current_id, drop_current, set_current, try_current}; + //////////////////////////////////////////////////////////////////////////////// // Thread-local storage //////////////////////////////////////////////////////////////////////////////// @@ -472,7 +477,11 @@ impl Builder { amt }); - let my_thread = name.map_or_else(Thread::new_unnamed, Thread::new); + let id = ThreadId::new(); + let my_thread = match name { + Some(name) => Thread::new(id, name.into()), + None => Thread::new_unnamed(id), + }; let their_thread = my_thread.clone(); let my_packet: Arc<Packet<'scope, T>> = Arc::new(Packet { @@ -510,6 +519,9 @@ impl Builder { let f = MaybeDangling::new(f); let main = move || { + // Immediately store the thread handle to avoid setting it or its ID + // twice, which would cause an abort. + set_current(their_thread.clone()); if let Some(name) = their_thread.cname() { imp::Thread::set_name(name); } @@ -517,7 +529,6 @@ impl Builder { crate::io::set_output_capture(output_capture); let f = f.into_inner(); - set_current(their_thread); let try_result = panic::catch_unwind(panic::AssertUnwindSafe(|| { crate::sys::backtrace::__rust_begin_short_backtrace(f) })); @@ -665,6 +676,19 @@ impl Builder { /// println!("{result}"); /// ``` /// +/// # Notes +/// +/// This function has the same minimal guarantee regarding "foreign" unwinding operations (e.g. +/// an exception thrown from C++ code, or a `panic!` in Rust code compiled or linked with a +/// different runtime) as [`catch_unwind`]; namely, if the thread created with `thread::spawn` +/// unwinds all the way to the root with such an exception, one of two behaviors are possible, +/// and it is unspecified which will occur: +/// +/// * The process aborts. +/// * The process does not abort, and [`join`] will return a `Result::Err` +/// containing an opaque type. +/// +/// [`catch_unwind`]: ../../std/panic/fn.catch_unwind.html /// [`channels`]: crate::sync::mpsc /// [`join`]: JoinHandle::join /// [`Err`]: crate::result::Result::Err @@ -678,84 +702,6 @@ where Builder::new().spawn(f).expect("failed to spawn thread") } -thread_local! { - // Invariant: `CURRENT` and `CURRENT_ID` will always be initialized together. - // If `CURRENT` is initialized, then `CURRENT_ID` will hold the same value - // as `CURRENT.id()`. - static CURRENT: OnceCell<Thread> = const { OnceCell::new() }; - static CURRENT_ID: Cell<Option<ThreadId>> = const { Cell::new(None) }; -} - -/// Sets the thread handle for the current thread. -/// -/// Aborts if the handle has been set already to reduce code size. -pub(crate) fn set_current(thread: Thread) { - let tid = thread.id(); - // Using `unwrap` here can add ~3kB to the binary size. We have complete - // control over where this is called, so just abort if there is a bug. - CURRENT.with(|current| match current.set(thread) { - Ok(()) => CURRENT_ID.set(Some(tid)), - Err(_) => rtabort!("thread::set_current should only be called once per thread"), - }); -} - -/// Gets a handle to the thread that invokes it. -/// -/// In contrast to the public `current` function, this will not panic if called -/// from inside a TLS destructor. -pub(crate) fn try_current() -> Option<Thread> { - CURRENT - .try_with(|current| { - current - .get_or_init(|| { - let thread = Thread::new_unnamed(); - CURRENT_ID.set(Some(thread.id())); - thread - }) - .clone() - }) - .ok() -} - -/// Gets the id of the thread that invokes it. -#[inline] -pub(crate) fn current_id() -> ThreadId { - CURRENT_ID.get().unwrap_or_else(|| { - // If `CURRENT_ID` isn't initialized yet, then `CURRENT` must also not be initialized. - // `current()` will initialize both `CURRENT` and `CURRENT_ID` so subsequent calls to - // `current_id()` will succeed immediately. - current().id() - }) -} - -/// Gets a handle to the thread that invokes it. -/// -/// # Examples -/// -/// Getting a handle to the current thread with `thread::current()`: -/// -/// ``` -/// use std::thread; -/// -/// let handler = thread::Builder::new() -/// .name("named thread".into()) -/// .spawn(|| { -/// let handle = thread::current(); -/// assert_eq!(handle.name(), Some("named thread")); -/// }) -/// .unwrap(); -/// -/// handler.join().unwrap(); -/// ``` -#[must_use] -#[stable(feature = "rust1", since = "1.0.0")] -pub fn current() -> Thread { - try_current().expect( - "use of std::thread::current() is not possible \ - after the thread's local data has been destroyed", - ) -} - /// Cooperatively gives up a timeslice to the OS scheduler. /// /// This calls the underlying OS scheduler's yield primitive, signaling @@ -1213,8 +1159,11 @@ pub fn park_timeout(dur: Duration) { pub struct ThreadId(NonZero<u64>); impl ThreadId { + // DO NOT rely on this value. + const MAIN_THREAD: ThreadId = ThreadId(unsafe { NonZero::new_unchecked(1) }); + // Generate a new unique thread ID. - fn new() -> ThreadId { + pub(crate) fn new() -> ThreadId { #[cold] fn exhausted() -> ! { panic!("failed to generate unique thread ID: bitspace exhausted") @@ -1224,7 +1173,7 @@ impl ThreadId { if #[cfg(target_has_atomic = "64")] { use crate::sync::atomic::AtomicU64; - static COUNTER: AtomicU64 = AtomicU64::new(0); + static COUNTER: AtomicU64 = AtomicU64::new(1); let mut last = COUNTER.load(Ordering::Relaxed); loop { @@ -1240,7 +1189,7 @@ impl ThreadId { } else { use crate::sync::{Mutex, PoisonError}; - static COUNTER: Mutex<u64> = Mutex::new(0); + static COUNTER: Mutex<u64> = Mutex::new(1); let mut counter = COUNTER.lock().unwrap_or_else(PoisonError::into_inner); let Some(id) = counter.checked_add(1) else { @@ -1257,6 +1206,11 @@ impl ThreadId { } } + #[cfg(not(target_thread_local))] + fn from_u64(v: u64) -> Option<ThreadId> { + NonZero::new(v).map(ThreadId) + } + /// This returns a numeric identifier for the thread identified by this /// `ThreadId`. /// @@ -1357,27 +1311,27 @@ impl Inner { /// should instead use a function like `spawn` to create new threads, see the /// docs of [`Builder`] and [`spawn`] for more details. /// -/// [`thread::current`]: current +/// [`thread::current`]: current::current pub struct Thread { inner: Pin<Arc<Inner>>, } impl Thread { /// Used only internally to construct a thread object without spawning. - pub(crate) fn new(name: String) -> Thread { - Self::new_inner(ThreadName::Other(name.into())) + pub(crate) fn new(id: ThreadId, name: String) -> Thread { + Self::new_inner(id, ThreadName::Other(name.into())) } - pub(crate) fn new_unnamed() -> Thread { - Self::new_inner(ThreadName::Unnamed) + pub(crate) fn new_unnamed(id: ThreadId) -> Thread { + Self::new_inner(id, ThreadName::Unnamed) } // Used in runtime to construct main thread pub(crate) fn new_main() -> Thread { - Self::new_inner(ThreadName::Main) + Self::new_inner(ThreadId::MAIN_THREAD, ThreadName::Main) } - fn new_inner(name: ThreadName) -> Thread { + fn new_inner(id: ThreadId, name: ThreadName) -> Thread { // We have to use `unsafe` here to construct the `Parker` in-place, // which is required for the UNIX implementation. // @@ -1386,9 +1340,9 @@ impl Thread { let inner = unsafe { let mut arc = Arc::<Inner>::new_uninit(); let ptr = Arc::get_mut_unchecked(&mut arc).as_mut_ptr(); - addr_of_mut!((*ptr).name).write(name); - addr_of_mut!((*ptr).id).write(ThreadId::new()); - Parker::new_in_place(addr_of_mut!((*ptr).parker)); + (&raw mut (*ptr).name).write(name); + (&raw mut (*ptr).id).write(id); + Parker::new_in_place(&raw mut (*ptr).parker); Pin::new_unchecked(arc.assume_init()) }; @@ -1785,7 +1739,7 @@ impl<T> JoinHandle<T> { /// operations that happen after `join` returns. /// /// If the associated thread panics, [`Err`] is returned with the parameter given - /// to [`panic!`]. + /// to [`panic!`] (though see the Notes below). /// /// [`Err`]: crate::result::Result::Err /// [atomic memory orderings]: crate::sync::atomic @@ -1807,6 +1761,18 @@ impl<T> JoinHandle<T> { /// }).unwrap(); /// join_handle.join().expect("Couldn't join on the associated thread"); /// ``` + /// + /// # Notes + /// + /// If a "foreign" unwinding operation (e.g. an exception thrown from C++ + /// code, or a `panic!` in Rust code compiled or linked with a different + /// runtime) unwinds all the way to the thread root, the process may be + /// aborted; see the Notes on [`thread::spawn`]. If the process is not + /// aborted, this function will return a `Result::Err` containing an opaque + /// type. + /// + /// [`catch_unwind`]: ../../std/panic/fn.catch_unwind.html + /// [`thread::spawn`]: spawn #[stable(feature = "rust1", since = "1.0.0")] pub fn join(self) -> Result<T> { self.0.join() |