diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs index b5450d0a20cf2..4308b7114994f 100644 --- a/library/std/src/lib.rs +++ b/library/std/src/lib.rs @@ -365,7 +365,6 @@ #![feature(std_internals)] #![feature(str_internals)] #![feature(strict_provenance_atomic_ptr)] -#![feature(sync_unsafe_cell)] #![feature(ub_checks)] // tidy-alphabetical-end // diff --git a/library/std/src/rt.rs b/library/std/src/rt.rs index b2492238bd37b..80e7c3c026bd7 100644 --- a/library/std/src/rt.rs +++ b/library/std/src/rt.rs @@ -110,7 +110,7 @@ unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) { // handle does not match the current ID, we should attempt to use the // current thread ID here instead of unconditionally creating a new // one. Also see #130210. - let thread = unsafe { Thread::new_main(thread::current_id()) }; + let thread = Thread::new_main(thread::current_id()); if let Err(_thread) = thread::set_current(thread) { // `thread::current` will create a new handle if none has been set yet. // Thus, if someone uses it before main, this call will fail. That's a diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs index 227ee9d64f375..d12219b31b265 100644 --- a/library/std/src/thread/mod.rs +++ b/library/std/src/thread/mod.rs @@ -158,12 +158,9 @@ #[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))] mod tests; -use core::cell::SyncUnsafeCell; -use core::ffi::CStr; -use core::mem::MaybeUninit; - use crate::any::Any; use crate::cell::UnsafeCell; +use crate::ffi::CStr; use crate::marker::PhantomData; use crate::mem::{self, ManuallyDrop, forget}; use crate::num::NonZero; @@ -1128,7 +1125,7 @@ pub fn park_timeout(dur: Duration) { let guard = PanicGuard; // SAFETY: park_timeout is called on the parker owned by this thread. unsafe { - current().0.parker().park_timeout(dur); + current().inner.as_ref().parker().park_timeout(dur); } // No panic occurred, do not abort. forget(guard); @@ -1235,31 +1232,30 @@ impl ThreadId { // Thread //////////////////////////////////////////////////////////////////////////////// +/// The internal representation of a `Thread`'s name. +enum ThreadName { + Main, + Other(ThreadNameString), + Unnamed, +} + // This module ensures private fields are kept private, which is necessary to enforce the safety requirements. mod thread_name_string { use core::str; + use super::ThreadName; use crate::ffi::{CStr, CString}; /// Like a `String` it's guaranteed UTF-8 and like a `CString` it's null terminated. pub(crate) struct ThreadNameString { inner: CString, } - - impl ThreadNameString { - pub fn as_str(&self) -> &str { - // SAFETY: `self.inner` is only initialised via `String`, which upholds the validity invariant of `str`. - unsafe { str::from_utf8_unchecked(self.inner.to_bytes()) } - } - } - impl core::ops::Deref for ThreadNameString { type Target = CStr; fn deref(&self) -> &CStr { &self.inner } } - impl From for ThreadNameString { fn from(s: String) -> Self { Self { @@ -1267,82 +1263,34 @@ mod thread_name_string { } } } + impl ThreadName { + pub fn as_cstr(&self) -> Option<&CStr> { + match self { + ThreadName::Main => Some(c"main"), + ThreadName::Other(other) => Some(other), + ThreadName::Unnamed => None, + } + } + + pub fn as_str(&self) -> Option<&str> { + // SAFETY: `as_cstr` can only return `Some` for a fixed CStr or a `ThreadNameString`, + // which is guaranteed to be UTF-8. + self.as_cstr().map(|s| unsafe { str::from_utf8_unchecked(s.to_bytes()) }) + } + } } pub(crate) use thread_name_string::ThreadNameString; -static MAIN_THREAD_INFO: SyncUnsafeCell<(MaybeUninit, MaybeUninit)> = - SyncUnsafeCell::new((MaybeUninit::uninit(), MaybeUninit::uninit())); - -/// The internal representation of a `Thread` that is not the main thread. -struct OtherInner { - name: Option, +/// The internal representation of a `Thread` handle +struct Inner { + name: ThreadName, // Guaranteed to be UTF-8 id: ThreadId, parker: Parker, } -/// The internal representation of a `Thread` handle. -#[derive(Clone)] -enum Inner { - /// Represents the main thread. May only be constructed by Thread::new_main. - Main(&'static (ThreadId, Parker)), - /// Represents any other thread. - Other(Pin>), -} - impl Inner { - fn id(&self) -> ThreadId { - match self { - Self::Main((thread_id, _)) => *thread_id, - Self::Other(other) => other.id, - } - } - - fn cname(&self) -> Option<&CStr> { - match self { - Self::Main(_) => Some(c"main"), - Self::Other(other) => other.name.as_deref(), - } - } - - fn name(&self) -> Option<&str> { - match self { - Self::Main(_) => Some("main"), - Self::Other(other) => other.name.as_ref().map(ThreadNameString::as_str), - } - } - - fn into_raw(self) -> *const () { - match self { - // Just return the pointer to `MAIN_THREAD_INFO`. - Self::Main(ptr) => crate::ptr::from_ref(ptr).cast(), - Self::Other(arc) => { - // Safety: We only expose an opaque pointer, which maintains the `Pin` invariant. - let inner = unsafe { Pin::into_inner_unchecked(arc) }; - Arc::into_raw(inner) as *const () - } - } - } - - /// # Safety - /// - /// See [`Thread::from_raw`]. - unsafe fn from_raw(ptr: *const ()) -> Self { - // If the pointer is to `MAIN_THREAD_INFO`, we know it is the `Main` variant. - if crate::ptr::eq(ptr.cast(), &MAIN_THREAD_INFO) { - Self::Main(unsafe { &*ptr.cast() }) - } else { - // Safety: Upheld by caller - Self::Other(unsafe { Pin::new_unchecked(Arc::from_raw(ptr as *const OtherInner)) }) - } - } - - fn parker(&self) -> Pin<&Parker> { - match self { - Self::Main((_, parker_ref)) => Pin::static_ref(parker_ref), - Self::Other(inner) => unsafe { - Pin::map_unchecked(inner.as_ref(), |inner| &inner.parker) - }, - } + fn parker(self: Pin<&Self>) -> Pin<&Parker> { + unsafe { Pin::map_unchecked(self, |inner| &inner.parker) } } } @@ -1366,47 +1314,33 @@ impl Inner { /// docs of [`Builder`] and [`spawn`] for more details. /// /// [`thread::current`]: current::current -pub struct Thread(Inner); +pub struct Thread { + inner: Pin>, +} impl Thread { /// Used only internally to construct a thread object without spawning. pub(crate) fn new(id: ThreadId, name: String) -> Thread { - Self::new_inner(id, Some(ThreadNameString::from(name))) + Self::new_inner(id, ThreadName::Other(name.into())) } pub(crate) fn new_unnamed(id: ThreadId) -> Thread { - Self::new_inner(id, None) + Self::new_inner(id, ThreadName::Unnamed) } - /// Used in runtime to construct main thread - /// - /// # Safety - /// - /// This must only ever be called once, and must be called on the main thread. - pub(crate) unsafe fn new_main(thread_id: ThreadId) -> Thread { - // Safety: As this is only called once and on the main thread, nothing else is accessing MAIN_THREAD_INFO - // as the only other read occurs in `main_thread_info` *after* the main thread has been constructed, - // and this function is the only one that constructs the main thread. - // - // Pre-main thread spawning cannot hit this either, as the caller promises that this is only called on the main thread. - let main_thread_info = unsafe { &mut *MAIN_THREAD_INFO.get() }; - - unsafe { Parker::new_in_place((&raw mut main_thread_info.1).cast()) }; - main_thread_info.0.write(thread_id); - - // Store a `'static` ref to the initialised ThreadId and Parker, - // to avoid having to repeatedly prove initialisation. - Self(Inner::Main(unsafe { &*MAIN_THREAD_INFO.get().cast() })) + /// Constructs the thread handle for the main thread. + pub(crate) fn new_main(id: ThreadId) -> Thread { + Self::new_inner(id, ThreadName::Main) } - fn new_inner(id: ThreadId, name: Option) -> 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. // // SAFETY: We pin the Arc immediately after creation, so its address never // changes. let inner = unsafe { - let mut arc = Arc::::new_uninit(); + let mut arc = Arc::::new_uninit(); let ptr = Arc::get_mut_unchecked(&mut arc).as_mut_ptr(); (&raw mut (*ptr).name).write(name); (&raw mut (*ptr).id).write(id); @@ -1414,7 +1348,7 @@ impl Thread { Pin::new_unchecked(arc.assume_init()) }; - Self(Inner::Other(inner)) + Thread { inner } } /// Like the public [`park`], but callable on any handle. This is used to @@ -1423,7 +1357,7 @@ impl Thread { /// # Safety /// May only be called from the thread to which this handle belongs. pub(crate) unsafe fn park(&self) { - unsafe { self.0.parker().park() } + unsafe { self.inner.as_ref().parker().park() } } /// Atomically makes the handle's token available if it is not already. @@ -1459,7 +1393,7 @@ impl Thread { #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn unpark(&self) { - self.0.parker().unpark(); + self.inner.as_ref().parker().unpark(); } /// Gets the thread's unique identifier. @@ -1479,7 +1413,7 @@ impl Thread { #[stable(feature = "thread_id", since = "1.19.0")] #[must_use] pub fn id(&self) -> ThreadId { - self.0.id() + self.inner.id } /// Gets the thread's name. @@ -1522,11 +1456,7 @@ impl Thread { #[stable(feature = "rust1", since = "1.0.0")] #[must_use] pub fn name(&self) -> Option<&str> { - self.0.name() - } - - fn cname(&self) -> Option<&CStr> { - self.0.cname() + self.inner.name.as_str() } /// Consumes the `Thread`, returning a raw pointer. @@ -1550,7 +1480,9 @@ impl Thread { /// ``` #[unstable(feature = "thread_raw", issue = "97523")] pub fn into_raw(self) -> *const () { - self.0.into_raw() + // Safety: We only expose an opaque pointer, which maintains the `Pin` invariant. + let inner = unsafe { Pin::into_inner_unchecked(self.inner) }; + Arc::into_raw(inner) as *const () } /// Constructs a `Thread` from a raw pointer. @@ -1572,7 +1504,11 @@ impl Thread { #[unstable(feature = "thread_raw", issue = "97523")] pub unsafe fn from_raw(ptr: *const ()) -> Thread { // Safety: Upheld by caller. - unsafe { Thread(Inner::from_raw(ptr)) } + unsafe { Thread { inner: Pin::new_unchecked(Arc::from_raw(ptr as *const Inner)) } } + } + + fn cname(&self) -> Option<&CStr> { + self.inner.name.as_cstr() } } diff --git a/tests/debuginfo/thread.rs b/tests/debuginfo/thread.rs index dc8cb0832192b..0415f586f5d90 100644 --- a/tests/debuginfo/thread.rs +++ b/tests/debuginfo/thread.rs @@ -12,15 +12,15 @@ // cdb-check:join_handle,d [Type: std::thread::JoinHandle >] // cdb-check: [...] __0 [Type: std::thread::JoinInner >] // -// cdb-command:dx -r3 t,d +// cdb-command:dx t,d // cdb-check:t,d : [...] [Type: std::thread::Thread *] -// cdb-check: [...] __0 : Other [Type: enum2$] -// cdb-check: [...] __0 [Type: core::pin::Pin >] +// cdb-check:[...] inner [...][Type: core::pin::Pin >] use std::thread; #[allow(unused_variables)] -fn main() { +fn main() +{ let join_handle = thread::spawn(|| { println!("Initialize a thread"); }); diff --git a/tests/rustdoc/demo-allocator-54478.rs b/tests/rustdoc/demo-allocator-54478.rs index 80acfc0ff58a1..dd98e80f03ade 100644 --- a/tests/rustdoc/demo-allocator-54478.rs +++ b/tests/rustdoc/demo-allocator-54478.rs @@ -40,7 +40,6 @@ //! } //! //! fn main() { -//! drop(String::from("An allocation")); //! assert!(unsafe { HIT }); //! } //! ```