diff --git a/library/std/src/panicking.rs b/library/std/src/panicking.rs index 31dbe86b66c..f46e1e171d2 100644 --- a/library/std/src/panicking.rs +++ b/library/std/src/panicking.rs @@ -21,7 +21,6 @@ use crate::sync::atomic::{AtomicBool, Ordering}; use crate::sync::{PoisonError, RwLock}; use crate::sys::stdio::panic_output; use crate::sys_common::backtrace; -use crate::sys_common::thread_info; use crate::thread; #[cfg(not(test))] @@ -256,7 +255,7 @@ fn default_hook(info: &PanicInfo<'_>) { None => "Box", }, }; - let thread = thread_info::current_thread(); + let thread = thread::try_current(); let name = thread.as_ref().and_then(|t| t.name()).unwrap_or(""); let write = |err: &mut dyn crate::io::Write| { diff --git a/library/std/src/rt.rs b/library/std/src/rt.rs index 335944845ae..0bafd9f352e 100644 --- a/library/std/src/rt.rs +++ b/library/std/src/rt.rs @@ -24,8 +24,7 @@ pub use core::panicking::{panic_display, panic_fmt}; use crate::sync::Once; use crate::sys; -use crate::sys_common::thread_info; -use crate::thread::Thread; +use crate::thread::{self, Thread}; // Prints to the "panic output", depending on the platform this may be: // - the standard error output @@ -96,13 +95,12 @@ unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) { unsafe { sys::init(argc, argv, sigpipe); - let main_guard = sys::thread::guard::init(); // Next, set up the current Thread with the guard information we just // created. Note that this isn't necessary in general for new threads, // but we just do this to name the main thread and to give it correct // info about the stack bounds. let thread = Thread::new(Some(rtunwrap!(Ok, CString::new("main")))); - thread_info::set(main_guard, thread); + thread::set_current(thread); } } diff --git a/library/std/src/sys/pal/hermit/thread.rs b/library/std/src/sys/pal/hermit/thread.rs index cf45b9c2396..c896261ea35 100644 --- a/library/std/src/sys/pal/hermit/thread.rs +++ b/library/std/src/sys/pal/hermit/thread.rs @@ -104,13 +104,3 @@ impl Thread { pub fn available_parallelism() -> io::Result> { unsafe { Ok(NonZero::new_unchecked(abi::get_processor_count())) } } - -pub mod guard { - pub type Guard = !; - pub unsafe fn current() -> Option { - None - } - pub unsafe fn init() -> Option { - None - } -} diff --git a/library/std/src/sys/pal/itron/thread.rs b/library/std/src/sys/pal/itron/thread.rs index 814a102dd09..2cad75cc315 100644 --- a/library/std/src/sys/pal/itron/thread.rs +++ b/library/std/src/sys/pal/itron/thread.rs @@ -312,16 +312,6 @@ impl Drop for Thread { } } -pub mod guard { - pub type Guard = !; - pub unsafe fn current() -> Option { - None - } - pub unsafe fn init() -> Option { - None - } -} - /// Terminate and delete the specified task. /// /// This function will abort if `deleted_task` refers to the calling task. diff --git a/library/std/src/sys/pal/sgx/thread.rs b/library/std/src/sys/pal/sgx/thread.rs index 77f68bf7334..ef07f6e6a26 100644 --- a/library/std/src/sys/pal/sgx/thread.rs +++ b/library/std/src/sys/pal/sgx/thread.rs @@ -149,13 +149,3 @@ impl Thread { pub fn available_parallelism() -> io::Result> { unsupported() } - -pub mod guard { - pub type Guard = !; - pub unsafe fn current() -> Option { - None - } - pub unsafe fn init() -> Option { - None - } -} diff --git a/library/std/src/sys/pal/teeos/thread.rs b/library/std/src/sys/pal/teeos/thread.rs index b76bcf9bbb0..fb4b74ba3c3 100644 --- a/library/std/src/sys/pal/teeos/thread.rs +++ b/library/std/src/sys/pal/teeos/thread.rs @@ -151,18 +151,6 @@ pub fn available_parallelism() -> io::Result> { )) } -// stub -pub mod guard { - use crate::ops::Range; - pub type Guard = Range; - pub unsafe fn current() -> Option { - None - } - pub unsafe fn init() -> Option { - None - } -} - fn min_stack_size(_: *const libc::pthread_attr_t) -> usize { libc::PTHREAD_STACK_MIN.try_into().expect("Infallible") } diff --git a/library/std/src/sys/pal/uefi/thread.rs b/library/std/src/sys/pal/uefi/thread.rs index b3a4f9c53e3..ca7b1efc269 100644 --- a/library/std/src/sys/pal/uefi/thread.rs +++ b/library/std/src/sys/pal/uefi/thread.rs @@ -52,13 +52,3 @@ pub fn available_parallelism() -> io::Result> { // UEFI is single threaded Ok(NonZero::new(1).unwrap()) } - -pub mod guard { - pub type Guard = !; - pub unsafe fn current() -> Option { - None - } - pub unsafe fn init() -> Option { - None - } -} diff --git a/library/std/src/sys/pal/unix/thread.rs b/library/std/src/sys/pal/unix/thread.rs index 06b46b3c122..badedaa8ae9 100644 --- a/library/std/src/sys/pal/unix/thread.rs +++ b/library/std/src/sys/pal/unix/thread.rs @@ -729,17 +729,6 @@ mod cgroups { } } -pub mod guard { - use crate::ops::Range; - pub type Guard = Range; - pub unsafe fn current() -> Option { - None - } - pub unsafe fn init() -> Option { - None - } -} - // glibc >= 2.15 has a __pthread_get_minstack() function that returns // PTHREAD_STACK_MIN plus bytes needed for thread-local storage. // We need that information to avoid blowing up when a small stack diff --git a/library/std/src/sys/pal/unsupported/thread.rs b/library/std/src/sys/pal/unsupported/thread.rs index b3a91ee1d4c..d3f2fa35b92 100644 --- a/library/std/src/sys/pal/unsupported/thread.rs +++ b/library/std/src/sys/pal/unsupported/thread.rs @@ -38,13 +38,3 @@ impl Thread { pub fn available_parallelism() -> io::Result> { unsupported() } - -pub mod guard { - pub type Guard = !; - pub unsafe fn current() -> Option { - None - } - pub unsafe fn init() -> Option { - None - } -} diff --git a/library/std/src/sys/pal/wasi/thread.rs b/library/std/src/sys/pal/wasi/thread.rs index 4b116052f8f..940f0c8423a 100644 --- a/library/std/src/sys/pal/wasi/thread.rs +++ b/library/std/src/sys/pal/wasi/thread.rs @@ -193,13 +193,3 @@ impl Thread { pub fn available_parallelism() -> io::Result> { unsupported() } - -pub mod guard { - pub type Guard = !; - pub unsafe fn current() -> Option { - None - } - pub unsafe fn init() -> Option { - None - } -} diff --git a/library/std/src/sys/pal/windows/thread.rs b/library/std/src/sys/pal/windows/thread.rs index 970bd9c6ce7..80eee4e078d 100644 --- a/library/std/src/sys/pal/windows/thread.rs +++ b/library/std/src/sys/pal/windows/thread.rs @@ -144,14 +144,3 @@ pub fn available_parallelism() -> io::Result> { cpus => Ok(unsafe { NonZero::new_unchecked(cpus) }), } } - -#[cfg_attr(test, allow(dead_code))] -pub mod guard { - pub type Guard = !; - pub unsafe fn current() -> Option { - None - } - pub unsafe fn init() -> Option { - None - } -} diff --git a/library/std/src/sys/pal/xous/thread.rs b/library/std/src/sys/pal/xous/thread.rs index f95ceb7343b..c1fd1c0d653 100644 --- a/library/std/src/sys/pal/xous/thread.rs +++ b/library/std/src/sys/pal/xous/thread.rs @@ -140,13 +140,3 @@ pub fn available_parallelism() -> io::Result> { // We're unicore right now. Ok(unsafe { NonZero::new_unchecked(1) }) } - -pub mod guard { - pub type Guard = !; - pub unsafe fn current() -> Option { - None - } - pub unsafe fn init() -> Option { - None - } -} diff --git a/library/std/src/sys/sync/rwlock/queue.rs b/library/std/src/sys/sync/rwlock/queue.rs index dce966086b8..d1918855797 100644 --- a/library/std/src/sys/sync/rwlock/queue.rs +++ b/library/std/src/sys/sync/rwlock/queue.rs @@ -115,8 +115,7 @@ use crate::sync::atomic::{ AtomicBool, AtomicPtr, Ordering::{AcqRel, Acquire, Relaxed, Release}, }; -use crate::sys_common::thread_info; -use crate::thread::Thread; +use crate::thread::{self, Thread}; // Locking uses exponential backoff. `SPIN_COUNT` indicates how many times the // locking operation will be retried. @@ -203,8 +202,7 @@ impl Node { fn prepare(&mut self) { // Fall back to creating an unnamed `Thread` handle to allow locking in // TLS destructors. - self.thread - .get_or_init(|| thread_info::current_thread().unwrap_or_else(|| Thread::new(None))); + self.thread.get_or_init(|| thread::try_current().unwrap_or_else(|| Thread::new(None))); self.completed = AtomicBool::new(false); } diff --git a/library/std/src/sys_common/mod.rs b/library/std/src/sys_common/mod.rs index 5410f135a73..5abf201aa20 100644 --- a/library/std/src/sys_common/mod.rs +++ b/library/std/src/sys_common/mod.rs @@ -26,7 +26,6 @@ pub mod io; pub mod lazy_box; pub mod process; pub mod thread; -pub mod thread_info; pub mod thread_local_dtor; pub mod thread_parking; pub mod wstr; diff --git a/library/std/src/sys_common/thread_info.rs b/library/std/src/sys_common/thread_info.rs deleted file mode 100644 index ec1428ea40e..00000000000 --- a/library/std/src/sys_common/thread_info.rs +++ /dev/null @@ -1,53 +0,0 @@ -#![allow(dead_code)] // stack_guard isn't used right now on all platforms - -use crate::cell::OnceCell; -use crate::sys; -use crate::sys::thread::guard::Guard; -use crate::thread::Thread; - -struct ThreadInfo { - stack_guard: OnceCell, - thread: OnceCell, -} - -thread_local! { - static THREAD_INFO: ThreadInfo = const { ThreadInfo { - stack_guard: OnceCell::new(), - thread: OnceCell::new() - } }; -} - -impl ThreadInfo { - fn with(f: F) -> Option - where - F: FnOnce(&Thread, &OnceCell) -> R, - { - THREAD_INFO - .try_with(move |thread_info| { - let thread = - thread_info.thread.get_or_init(|| Thread::new(sys::thread::Thread::get_name())); - f(thread, &thread_info.stack_guard) - }) - .ok() - } -} - -pub fn current_thread() -> Option { - ThreadInfo::with(|thread, _| thread.clone()) -} - -pub fn stack_guard() -> Option { - ThreadInfo::with(|_, guard| guard.get().cloned()).flatten() -} - -/// Set new thread info, panicking if it has already been initialized -#[allow(unreachable_code, unreachable_patterns)] // some platforms don't use stack_guard -pub fn set(stack_guard: Option, thread: Thread) { - THREAD_INFO.with(move |thread_info| { - rtassert!(thread_info.stack_guard.get().is_none() && thread_info.thread.get().is_none()); - if let Some(guard) = stack_guard { - thread_info.stack_guard.set(guard).unwrap(); - } - thread_info.thread.set(thread).unwrap(); - }); -} diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs index 85de2980133..f7eb92bc61e 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::UnsafeCell; +use crate::cell::{OnceCell, UnsafeCell}; use crate::ffi::{CStr, CString}; use crate::fmt; use crate::io; @@ -174,7 +174,6 @@ use crate::str; use crate::sync::Arc; use crate::sys::thread as imp; use crate::sys_common::thread; -use crate::sys_common::thread_info; use crate::sys_common::thread_parking::Parker; use crate::sys_common::{AsInner, IntoInner}; use crate::time::{Duration, Instant}; @@ -518,12 +517,8 @@ impl Builder { crate::io::set_output_capture(output_capture); - // SAFETY: we constructed `f` initialized. let f = f.into_inner(); - // SAFETY: the stack guard passed is the one for the current thread. - // This means the current thread's stack and the new thread's stack - // are properly set and protected from each other. - thread_info::set(unsafe { imp::guard::current() }, their_thread); + set_current(their_thread); let try_result = panic::catch_unwind(panic::AssertUnwindSafe(|| { crate::sys_common::backtrace::__rust_begin_short_backtrace(f) })); @@ -683,6 +678,27 @@ 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. +/// +/// Panics if the handle has been set already or when called from a TLS destructor. +pub(crate) fn set_current(thread: Thread) { + CURRENT.with(|current| current.set(thread).unwrap()); +} + +/// 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(imp::Thread::get_name())).clone()) + .ok() +} + /// Gets a handle to the thread that invokes it. /// /// # Examples @@ -705,7 +721,7 @@ where #[must_use] #[stable(feature = "rust1", since = "1.0.0")] pub fn current() -> Thread { - thread_info::current_thread().expect( + try_current().expect( "use of std::thread::current() is not possible \ after the thread's local data has been destroyed", )