From 7dd342ea68fcc3708c2225bbec57156c3e833b74 Mon Sep 17 00:00:00 2001 From: joboet Date: Thu, 18 Jul 2024 13:59:48 +0200 Subject: [PATCH] std: make `thread::current` available in all `thread_local!` destructors --- library/std/src/rt.rs | 33 +++-- library/std/src/sys/pal/hermit/mod.rs | 2 + library/std/src/sys/pal/hermit/thread.rs | 1 + .../std/src/sys/thread_local/guard/apple.rs | 1 + library/std/src/sys/thread_local/guard/key.rs | 39 +++++- .../std/src/sys/thread_local/guard/solid.rs | 5 +- .../std/src/sys/thread_local/guard/windows.rs | 8 +- library/std/src/sys/thread_local/key/xous.rs | 2 + library/std/src/sys/thread_local/mod.rs | 46 ++++--- .../std/src/sys/thread_local/native/mod.rs | 31 +++++ library/std/src/sys/thread_local/os.rs | 33 ++++- library/std/src/sys/thread_local/statik.rs | 33 ++++- library/std/src/thread/current.rs | 126 ++++++++++++++++++ library/std/src/thread/local/tests.rs | 33 ++++- library/std/src/thread/mod.rs | 92 ++++--------- 15 files changed, 383 insertions(+), 102 deletions(-) create mode 100644 library/std/src/thread/current.rs diff --git a/library/std/src/rt.rs b/library/std/src/rt.rs index deb4a8fa7eed0..692ea5e95e5a5 100644 --- a/library/std/src/rt.rs +++ b/library/std/src/rt.rs @@ -19,9 +19,11 @@ pub use crate::panicking::{begin_panic, panic_count}; pub use core::panicking::{panic_display, panic_fmt}; +use crate::any::Any; use crate::sync::Once; use crate::sys; use crate::thread::{self, Thread}; +use crate::{mem, panic}; // Prints to the "panic output", depending on the platform this may be: // - the standard error output @@ -64,6 +66,11 @@ macro_rules! rtunwrap { }; } +fn handle_rt_panic(e: Box) { + mem::forget(e); + rtabort!("initialization or cleanup bug"); +} + // One-time runtime initialization. // Runs before `main`. // SAFETY: must be called only once during runtime initialization. @@ -99,6 +106,20 @@ unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) { thread::set_current(thread); } +/// Clean up the thread-local runtime state. This *should* be run after all other +/// code managed by the Rust runtime, but will not cause UB if that condition is +/// not fulfilled. Also note that this function is not guaranteed to be run, but +/// skipping it will cause leaks and therefore is to be avoided. +pub(crate) fn thread_cleanup() { + // This function is run in situations where unwinding leads to an abort + // (think `extern "C"` functions). Abort here instead so that we can + // print a nice message. + panic::catch_unwind(|| { + crate::thread::drop_current(); + }) + .unwrap_or_else(handle_rt_panic); +} + // One-time runtime cleanup. // Runs after `main` or at program exit. // NOTE: this is not guaranteed to run, for example when the program aborts. @@ -121,11 +142,6 @@ fn lang_start_internal( argv: *const *const u8, sigpipe: u8, ) -> Result { - use crate::{mem, panic}; - let rt_abort = move |e| { - mem::forget(e); - rtabort!("initialization or cleanup bug"); - }; // Guard against the code called by this function from unwinding outside of the Rust-controlled // code, which is UB. This is a requirement imposed by a combination of how the // `#[lang="start"]` attribute is implemented as well as by the implementation of the panicking @@ -137,16 +153,17 @@ fn lang_start_internal( // prevent std from accidentally introducing a panic to these functions. Another is from // user code from `main` or, more nefariously, as described in e.g. issue #86030. // SAFETY: Only called once during runtime initialization. - panic::catch_unwind(move || unsafe { init(argc, argv, sigpipe) }).map_err(rt_abort)?; + panic::catch_unwind(move || unsafe { init(argc, argv, sigpipe) }) + .unwrap_or_else(handle_rt_panic); let ret_code = panic::catch_unwind(move || panic::catch_unwind(main).unwrap_or(101) as isize) .map_err(move |e| { mem::forget(e); rtabort!("drop of the panic payload panicked"); }); - panic::catch_unwind(cleanup).map_err(rt_abort)?; + panic::catch_unwind(cleanup).unwrap_or_else(handle_rt_panic); // Guard against multple threads calling `libc::exit` concurrently. // See the documentation for `unique_thread_exit` for more information. - panic::catch_unwind(|| crate::sys::exit_guard::unique_thread_exit()).map_err(rt_abort)?; + panic::catch_unwind(crate::sys::exit_guard::unique_thread_exit).unwrap_or_else(handle_rt_panic); ret_code } diff --git a/library/std/src/sys/pal/hermit/mod.rs b/library/std/src/sys/pal/hermit/mod.rs index 55583b89d6714..d60bbab386559 100644 --- a/library/std/src/sys/pal/hermit/mod.rs +++ b/library/std/src/sys/pal/hermit/mod.rs @@ -104,6 +104,8 @@ pub unsafe extern "C" fn runtime_entry( let result = main(argc as isize, argv); crate::sys::thread_local::destructors::run(); + crate::rt::thread_cleanup(); + hermit_abi::exit(result); } diff --git a/library/std/src/sys/pal/hermit/thread.rs b/library/std/src/sys/pal/hermit/thread.rs index a244b953d2a49..469ff0bd9930b 100644 --- a/library/std/src/sys/pal/hermit/thread.rs +++ b/library/std/src/sys/pal/hermit/thread.rs @@ -50,6 +50,7 @@ impl Thread { // run all destructors crate::sys::thread_local::destructors::run(); + crate::rt::thread_cleanup(); } } } diff --git a/library/std/src/sys/thread_local/guard/apple.rs b/library/std/src/sys/thread_local/guard/apple.rs index 6c27f7ae35cba..fa25b116622fc 100644 --- a/library/std/src/sys/thread_local/guard/apple.rs +++ b/library/std/src/sys/thread_local/guard/apple.rs @@ -26,6 +26,7 @@ pub fn enable() { unsafe extern "C" fn run_dtors(_: *mut u8) { unsafe { destructors::run(); + crate::rt::thread_cleanup(); } } } diff --git a/library/std/src/sys/thread_local/guard/key.rs b/library/std/src/sys/thread_local/guard/key.rs index 67c3ca8862767..abaa4df0253ef 100644 --- a/library/std/src/sys/thread_local/guard/key.rs +++ b/library/std/src/sys/thread_local/guard/key.rs @@ -3,10 +3,12 @@ //! that will run all native TLS destructors in the destructor list. use crate::ptr; -use crate::sys::thread_local::destructors; use crate::sys::thread_local::key::{set, LazyKey}; +#[cfg(target_thread_local)] pub fn enable() { + use crate::sys::thread_local::destructors; + static DTORS: LazyKey = LazyKey::new(Some(run)); // Setting the key value to something other than NULL will result in the @@ -18,6 +20,41 @@ pub fn enable() { unsafe extern "C" fn run(_: *mut u8) { unsafe { destructors::run(); + // On platforms with `__cxa_thread_atexit_impl`, `destructors::run` + // does nothing on newer systems as the TLS destructors are + // registered with the system. But because all of those platforms + // call the destructors of TLS keys after the registered ones, this + // function will still be run last (at the time of writing). + crate::rt::thread_cleanup(); + } + } +} + +/// On platforms with key-based TLS, the system runs the destructors for us. +/// We still have to make sure that [`crate::rt::thread_cleanup`] is called, +/// however. This is done by defering the execution of a TLS destructor to +/// the next round of destruction inside the TLS destructors. +#[cfg(not(target_thread_local))] +pub fn enable() { + const DEFER: *mut u8 = ptr::without_provenance_mut(1); + const RUN: *mut u8 = ptr::without_provenance_mut(2); + + static CLEANUP: LazyKey = LazyKey::new(Some(run)); + + unsafe { set(CLEANUP.force(), DEFER) } + + unsafe extern "C" fn run(state: *mut u8) { + if state == DEFER { + // Make sure that this function is run again in the next round of + // TLS destruction. If there is no futher round, there will be leaks, + // but that's okay, `thread_cleanup` is not guaranteed to be called. + unsafe { set(CLEANUP.force(), RUN) } + } else { + debug_assert_eq!(state, RUN); + // If the state is still RUN in the next round of TLS destruction, + // it means that no other TLS destructors defined by this runtime + // have been run, as they would have set the state to DEFER. + crate::rt::thread_cleanup(); } } } diff --git a/library/std/src/sys/thread_local/guard/solid.rs b/library/std/src/sys/thread_local/guard/solid.rs index b65d00c5b5fb7..1b44c2a33a552 100644 --- a/library/std/src/sys/thread_local/guard/solid.rs +++ b/library/std/src/sys/thread_local/guard/solid.rs @@ -18,6 +18,9 @@ pub fn enable() { } unsafe extern "C" fn tls_dtor(_unused: *mut u8) { - unsafe { destructors::run() }; + unsafe { + destructors::run(); + crate::rt::thread_cleanup(); + } } } diff --git a/library/std/src/sys/thread_local/guard/windows.rs b/library/std/src/sys/thread_local/guard/windows.rs index f6cd457046ffc..3db829f924278 100644 --- a/library/std/src/sys/thread_local/guard/windows.rs +++ b/library/std/src/sys/thread_local/guard/windows.rs @@ -92,13 +92,13 @@ unsafe extern "system" fn tls_callback(_h: *mut c_void, dw_reason: u32, _pv: *mu } if dw_reason == c::DLL_THREAD_DETACH || dw_reason == c::DLL_PROCESS_DETACH { - #[cfg(target_thread_local)] unsafe { + #[cfg(target_thread_local)] super::super::destructors::run(); - } - #[cfg(not(target_thread_local))] - unsafe { + #[cfg(not(target_thread_local))] super::super::key::run_dtors(); + + crate::rt::thread_cleanup(); } } } diff --git a/library/std/src/sys/thread_local/key/xous.rs b/library/std/src/sys/thread_local/key/xous.rs index 5a837a33e190e..45ca8e1aa5b00 100644 --- a/library/std/src/sys/thread_local/key/xous.rs +++ b/library/std/src/sys/thread_local/key/xous.rs @@ -213,4 +213,6 @@ unsafe fn run_dtors() { unsafe { cur = (*cur).next }; } } + + crate::rt::thread_cleanup(); } diff --git a/library/std/src/sys/thread_local/mod.rs b/library/std/src/sys/thread_local/mod.rs index 3d1b91a7ea095..600826c7c9935 100644 --- a/library/std/src/sys/thread_local/mod.rs +++ b/library/std/src/sys/thread_local/mod.rs @@ -31,12 +31,15 @@ cfg_if::cfg_if! { ))] { mod statik; pub use statik::{EagerStorage, LazyStorage, thread_local_inner}; + pub(crate) use statik::{LocalPointer, local_pointer}; } else if #[cfg(target_thread_local)] { mod native; pub use native::{EagerStorage, LazyStorage, thread_local_inner}; + pub(crate) use native::{LocalPointer, local_pointer}; } else { mod os; pub use os::{Storage, thread_local_inner}; + pub(crate) use os::{LocalPointer, local_pointer}; } } @@ -72,36 +75,47 @@ pub(crate) mod destructors { } /// This module provides a way to schedule the execution of the destructor list -/// on systems without a per-variable destructor system. -mod guard { +/// and the [runtime cleanup](crate::rt::thread_cleanup) function. Calling [enable] +/// should ensure that these functions are called at the right times. +pub(crate) mod guard { cfg_if::cfg_if! { if #[cfg(all(target_thread_local, target_vendor = "apple"))] { mod apple; - pub(super) use apple::enable; + pub(crate) use apple::enable; } else if #[cfg(target_os = "windows")] { mod windows; - pub(super) use windows::enable; + pub(crate) use windows::enable; } else if #[cfg(any( - all(target_family = "wasm", target_feature = "atomics"), + target_family = "wasm", + target_os = "uefi", + target_os = "zkvm", ))] { - pub(super) fn enable() { - // FIXME: Right now there is no concept of "thread exit", but - // this is likely going to show up at some point in the form of - // an exported symbol that the wasm runtime is going to be - // expected to call. For now we just leak everything, but if - // such a function starts to exist it will probably need to + pub(crate) fn enable() { + // FIXME: Right now there is no concept of "thread exit" on + // wasm, but this is likely going to show up at some point in + // the form of an exported symbol that the wasm runtime is going + // to be expected to call. For now we just leak everything, but + // if such a function starts to exist it will probably need to // iterate the destructor list with this function: #[allow(unused)] + #[cfg(not(all(target_family = "wasm", not(target_feature = "atomics"))))] use super::destructors::run; + #[allow(unused)] + use crate::rt::thread_cleanup; } - } else if #[cfg(target_os = "hermit")] { - pub(super) fn enable() {} + } else if #[cfg(any( + target_os = "hermit", + target_os = "xous", + ))] { + // `std` is the only runtime, so it just calls the destructor functions + // itself when the time comes. + pub(crate) fn enable() {} } else if #[cfg(target_os = "solid_asp3")] { mod solid; - pub(super) use solid::enable; - } else if #[cfg(all(target_thread_local, not(target_family = "wasm")))] { + pub(crate) use solid::enable; + } else { mod key; - pub(super) use key::enable; + pub(crate) use key::enable; } } } diff --git a/library/std/src/sys/thread_local/native/mod.rs b/library/std/src/sys/thread_local/native/mod.rs index 1cc45fe892dee..90c1041db4a5f 100644 --- a/library/std/src/sys/thread_local/native/mod.rs +++ b/library/std/src/sys/thread_local/native/mod.rs @@ -32,6 +32,9 @@ mod eager; mod lazy; +use crate::cell::Cell; +use crate::ptr; + pub use eager::Storage as EagerStorage; pub use lazy::Storage as LazyStorage; @@ -107,3 +110,31 @@ pub macro thread_local_inner { $crate::thread::local_impl::thread_local_inner!(@key $t, $($init)*); }, } + +#[rustc_macro_transparency = "semitransparent"] +pub(crate) macro local_pointer { + () => {}, + ($vis:vis static $name:ident; $($rest:tt)*) => { + #[thread_local] + $vis static $name: $crate::sys::thread_local::LocalPointer = $crate::sys::thread_local::LocalPointer::__new(); + $crate::sys::thread_local::local_pointer! { $($rest)* } + }, +} + +pub(crate) struct LocalPointer { + p: Cell<*mut ()>, +} + +impl LocalPointer { + pub const fn __new() -> LocalPointer { + LocalPointer { p: Cell::new(ptr::null_mut()) } + } + + pub fn get(&self) -> *mut () { + self.p.get() + } + + pub fn set(&self, p: *mut ()) { + self.p.set(p) + } +} diff --git a/library/std/src/sys/thread_local/os.rs b/library/std/src/sys/thread_local/os.rs index e06185f00690b..47a9832b973a8 100644 --- a/library/std/src/sys/thread_local/os.rs +++ b/library/std/src/sys/thread_local/os.rs @@ -1,8 +1,9 @@ use super::abort_on_dtor_unwind; +use super::guard; +use super::key::{get, set, Key, LazyKey}; use crate::cell::Cell; use crate::marker::PhantomData; use crate::ptr; -use crate::sys::thread_local::key::{get, set, Key, LazyKey}; #[doc(hidden)] #[allow_internal_unstable(thread_local_internals)] @@ -138,5 +139,35 @@ unsafe extern "C" fn destroy_value(ptr: *mut u8) { drop(ptr); // SAFETY: `key` is the TLS key `ptr` was stored under. unsafe { set(key, ptr::null_mut()) }; + // Make sure that the runtime cleanup will be performed + // after the next round of TLS destruction. + guard::enable(); }); } + +#[rustc_macro_transparency = "semitransparent"] +pub(crate) macro local_pointer { + () => {}, + ($vis:vis static $name:ident; $($rest:tt)*) => { + $vis static $name: $crate::sys::thread_local::LocalPointer = $crate::sys::thread_local::LocalPointer::__new(); + $crate::sys::thread_local::local_pointer! { $($rest)* } + }, +} + +pub(crate) struct LocalPointer { + key: LazyKey, +} + +impl LocalPointer { + pub const fn __new() -> LocalPointer { + LocalPointer { key: LazyKey::new(None) } + } + + pub fn get(&'static self) -> *mut () { + unsafe { get(self.key.force()) as *mut () } + } + + pub fn set(&'static self, p: *mut ()) { + unsafe { set(self.key.force(), p as *mut u8) } + } +} diff --git a/library/std/src/sys/thread_local/statik.rs b/library/std/src/sys/thread_local/statik.rs index 0f08cab1ae4ff..12c628f15ed9c 100644 --- a/library/std/src/sys/thread_local/statik.rs +++ b/library/std/src/sys/thread_local/statik.rs @@ -1,7 +1,8 @@ //! On some targets like wasm there's no threads, so no need to generate //! thread locals and we can instead just use plain statics! -use crate::cell::UnsafeCell; +use crate::cell::{Cell, UnsafeCell}; +use crate::ptr; #[doc(hidden)] #[allow_internal_unstable(thread_local_internals)] @@ -93,3 +94,33 @@ impl LazyStorage { // SAFETY: the target doesn't have threads. unsafe impl Sync for LazyStorage {} + +#[rustc_macro_transparency = "semitransparent"] +pub(crate) macro local_pointer { + () => {}, + ($vis:vis static $name:ident; $($rest:tt)*) => { + $vis static $name: $crate::sys::thread_local::LocalPointer = $crate::sys::thread_local::LocalPointer::__new(); + $crate::sys::thread_local::local_pointer! { $($rest)* } + }, +} + +pub(crate) struct LocalPointer { + p: Cell<*mut ()>, +} + +impl LocalPointer { + pub const fn __new() -> LocalPointer { + LocalPointer { p: Cell::new(ptr::null_mut()) } + } + + pub fn get(&self) -> *mut () { + self.p.get() + } + + pub fn set(&self, p: *mut ()) { + self.p.set(p) + } +} + +// SAFETY: the target doesn't have threads. +unsafe impl Sync for LocalPointer {} diff --git a/library/std/src/thread/current.rs b/library/std/src/thread/current.rs new file mode 100644 index 0000000000000..a0607b6c8b849 --- /dev/null +++ b/library/std/src/thread/current.rs @@ -0,0 +1,126 @@ +use super::Thread; +use crate::mem::ManuallyDrop; +use crate::ptr; +use crate::sys::thread_local::local_pointer; + +const NONE: *mut () = ptr::null_mut(); +const BUSY: *mut () = ptr::without_provenance_mut(1); +const DESTROYED: *mut () = ptr::without_provenance_mut(2); + +local_pointer! { + static CURRENT; +} + +/// 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) { + if CURRENT.get() != NONE { + // Using `panic` 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. + rtabort!("thread::set_current should only be called once per thread"); + } + + // Make sure that `crate::rt::thread_cleanup` will be run, which will + // call `drop_current`. + crate::sys::thread_local::guard::enable(); + CURRENT.set(thread.into_raw()); +} + +/// Gets a handle to the thread that invokes it, if the handle has been initialized. +pub(crate) fn try_current() -> Option { + let current = CURRENT.get(); + if current > DESTROYED { + unsafe { + let current = ManuallyDrop::new(Thread::from_raw(current)); + Some((*current).clone()) + } + } else { + None + } +} + +/// 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 { + let current = CURRENT.get(); + if current > DESTROYED { + unsafe { + let current = ManuallyDrop::new(Thread::from_raw(current)); + (*current).clone() + } + } else { + init_current(current) + } +} + +#[cold] +fn init_current(current: *mut ()) -> Thread { + if current == NONE { + // Make sure that `crate::rt::thread_cleanup` will be run, which will + // call `drop_current`. + crate::sys::thread_local::guard::enable(); + CURRENT.set(BUSY); + let thread = Thread::new_unnamed(); + CURRENT.set(thread.clone().into_raw()); + thread + } else if current == BUSY { + // BUSY exists solely for this check, but as it is in the slow path, the + // extra TLS write above shouldn't matter. The alternative is nearly always + // a stack overflow. + + // If you came across this message, contact the author of your allocator. + // If you are said author: A surprising amount of functions inside the + // standard library (e.g. `Mutex`, `thread_local!`, `File` when using long + // paths, even `panic!` when using unwinding), need memory allocation, so + // you'll get circular dependencies all over the place when using them. + // I (joboet) highly recommend using only APIs from core in your allocator + // and implementing your own system abstractions. Still, if you feel that + // a particular API should be entirely allocation-free, feel free to open + // an issue on the Rust repository, we'll see what we can do. + rtabort!( + "\n + Attempted to access thread-local data while allocating said data.\n + Do not access functions that allocate in the global allocator!\n + This is a bug in the global allocator.\n + " + ) + } else { + debug_assert_eq!(current, DESTROYED); + panic!( + "use of std::thread::current() is not possible after the thread's + local data has been destroyed" + ) + } +} + +/// This should be run in [`crate::rt::thread_cleanup`] to reset the thread +/// handle. +pub(crate) fn drop_current() { + let current = CURRENT.get(); + if current > DESTROYED { + unsafe { + CURRENT.set(DESTROYED); + drop(Thread::from_raw(current)); + } + } +} diff --git a/library/std/src/thread/local/tests.rs b/library/std/src/thread/local/tests.rs index 25019b554bb6a..54e9743d2e3b2 100644 --- a/library/std/src/thread/local/tests.rs +++ b/library/std/src/thread/local/tests.rs @@ -1,7 +1,7 @@ use crate::cell::{Cell, UnsafeCell}; use crate::sync::atomic::{AtomicU8, Ordering}; use crate::sync::{Arc, Condvar, Mutex}; -use crate::thread::{self, LocalKey}; +use crate::thread::{self, Builder, LocalKey}; use crate::thread_local; #[derive(Clone, Default)] @@ -340,3 +340,34 @@ fn join_orders_after_tls_destructors() { jh2.join().unwrap(); } } + +// Test that thread::current is still available in TLS destructors. +#[test] +fn thread_current_in_dtor() { + // Go through one round of TLS destruction first. + struct Defer; + impl Drop for Defer { + fn drop(&mut self) { + RETRIEVE.with(|_| {}); + } + } + + struct RetrieveName; + impl Drop for RetrieveName { + fn drop(&mut self) { + *NAME.lock().unwrap() = Some(thread::current().name().unwrap().to_owned()); + } + } + + static NAME: Mutex> = Mutex::new(None); + + thread_local! { + static DEFER: Defer = const { Defer }; + static RETRIEVE: RetrieveName = const { RetrieveName }; + } + + Builder::new().name("test".to_owned()).spawn(|| DEFER.with(|_| {})).unwrap().join().unwrap(); + let name = NAME.lock().unwrap(); + let name = name.as_ref().unwrap(); + assert_eq!(name, "test"); +} diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs index c8ee365392f85..1e62a23fc4c5f 100644 --- a/library/std/src/thread/mod.rs +++ b/library/std/src/thread/mod.rs @@ -159,7 +159,7 @@ mod tests; use crate::any::Any; -use crate::cell::{OnceCell, UnsafeCell}; +use crate::cell::UnsafeCell; use crate::env; use crate::ffi::{CStr, CString}; use crate::fmt; @@ -185,6 +185,12 @@ mod scoped; #[stable(feature = "scoped_threads", since = "1.63.0")] pub use scoped::{scope, Scope, ScopedJoinHandle}; +mod current; + +#[stable(feature = "rust1", since = "1.0.0")] +pub use current::current; +pub(crate) use current::{drop_current, set_current, try_current}; + //////////////////////////////////////////////////////////////////////////////// // Thread-local storage //////////////////////////////////////////////////////////////////////////////// @@ -192,22 +198,14 @@ pub use scoped::{scope, Scope, ScopedJoinHandle}; #[macro_use] mod local; -cfg_if::cfg_if! { - if #[cfg(test)] { - // Avoid duplicating the global state associated with thread-locals between this crate and - // realstd. Miri relies on this. - pub use realstd::thread::{local_impl, AccessError, LocalKey}; - } else { - #[stable(feature = "rust1", since = "1.0.0")] - pub use self::local::{AccessError, LocalKey}; - - // Implementation details used by the thread_local!{} macro. - #[doc(hidden)] - #[unstable(feature = "thread_local_internals", issue = "none")] - pub mod local_impl { - pub use crate::sys::thread_local::*; - } - } +#[stable(feature = "rust1", since = "1.0.0")] +pub use self::local::{AccessError, LocalKey}; + +// Implementation details used by the thread_local!{} macro. +#[doc(hidden)] +#[unstable(feature = "thread_local_internals", issue = "none")] +pub mod local_impl { + pub use crate::sys::thread_local::*; } //////////////////////////////////////////////////////////////////////////////// @@ -698,58 +696,6 @@ where Builder::new().spawn(f).expect("failed to spawn thread") } -thread_local! { - static CURRENT: OnceCell = const { OnceCell::new() }; -} - -/// 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) { - // 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(()) => {} - 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 { - CURRENT.try_with(|current| current.get_or_init(|| Thread::new_unnamed()).clone()).ok() -} - -/// 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 @@ -1352,6 +1298,14 @@ impl Thread { Thread { inner } } + fn into_raw(self) -> *mut () { + unsafe { Arc::into_raw(Pin::into_inner_unchecked(self.inner)) as *mut () } + } + + unsafe fn from_raw(ptr: *mut ()) -> Thread { + unsafe { Thread { inner: Pin::new_unchecked(Arc::from_raw(ptr as *const Inner)) } } + } + /// Like the public [`park`], but callable on any handle. This is used to /// allow parking in TLS destructors. ///