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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:03:36 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:03:36 +0000 |
commit | 17d40c6057c88f4c432b0d7bac88e1b84cb7e67f (patch) | |
tree | 3f66c4a5918660bb8a758ab6cda5ff8ee4f6cdcd /library/std/src/thread | |
parent | Adding upstream version 1.64.0+dfsg1. (diff) | |
download | rustc-upstream/1.65.0+dfsg1.tar.xz rustc-upstream/1.65.0+dfsg1.zip |
Adding upstream version 1.65.0+dfsg1.upstream/1.65.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | library/std/src/thread/local.rs | 3 | ||||
-rw-r--r-- | library/std/src/thread/mod.rs | 85 | ||||
-rw-r--r-- | library/std/src/thread/tests.rs | 50 |
3 files changed, 112 insertions, 26 deletions
diff --git a/library/std/src/thread/local.rs b/library/std/src/thread/local.rs index f4750cdf7..8aedfc4a6 100644 --- a/library/std/src/thread/local.rs +++ b/library/std/src/thread/local.rs @@ -1036,6 +1036,7 @@ pub mod fast { } #[doc(hidden)] +#[cfg(not(target_thread_local))] pub mod os { use super::lazy::LazyKeyInner; use crate::cell::Cell; @@ -1044,6 +1045,8 @@ pub mod os { use crate::ptr; use crate::sys_common::thread_local_key::StaticKey as OsStaticKey; + /// Use a regular global static to store this key; the state provided will then be + /// thread-local. pub struct Key<T> { // OS-TLS key that we'll use to key off. os: OsStaticKey, diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs index 44c8a50fd..ceea6986e 100644 --- a/library/std/src/thread/mod.rs +++ b/library/std/src/thread/mod.rs @@ -116,7 +116,7 @@ //! Threads are able to have associated names for identification purposes. By default, spawned //! threads are unnamed. To specify a name for a thread, build the thread with [`Builder`] and pass //! the desired thread name to [`Builder::name`]. To retrieve the thread name from within the -//! thread, use [`Thread::name`]. A couple examples of where the name of a thread gets used: +//! thread, use [`Thread::name`]. A couple of examples where the name of a thread gets used: //! //! * If a panic occurs in a named thread, the thread name will be printed in the panic message. //! * The thread name is provided to the OS where applicable (e.g., `pthread_setname_np` in @@ -170,7 +170,6 @@ use crate::ptr::addr_of_mut; use crate::str; use crate::sync::Arc; use crate::sys::thread as imp; -use crate::sys_common::mutex; use crate::sys_common::thread; use crate::sys_common::thread_info; use crate::sys_common::thread_parker::Parker; @@ -193,21 +192,31 @@ pub use scoped::{scope, Scope, ScopedJoinHandle}; #[stable(feature = "rust1", since = "1.0.0")] pub use self::local::{AccessError, LocalKey}; -// The types used by the thread_local! macro to access TLS keys. Note that there -// are two types, the "OS" type and the "fast" type. The OS thread local key -// type is accessed via platform-specific API calls and is slow, while the fast +// Select the type used by the thread_local! macro to access TLS keys. There +// are three types: "static", "fast", "OS". The "OS" thread local key +// type is accessed via platform-specific API calls and is slow, while the "fast" // key type is accessed via code generated via LLVM, where TLS keys are set up -// by the elf linker. Note that the OS TLS type is always available: on macOS -// the standard library is compiled with support for older platform versions -// where fast TLS was not available; end-user code is compiled with fast TLS -// where available, but both are needed. +// by the elf linker. "static" is for single-threaded platforms where a global +// static is sufficient. #[unstable(feature = "libstd_thread_internals", issue = "none")] #[cfg(target_thread_local)] +#[cfg(not(test))] #[doc(hidden)] pub use self::local::fast::Key as __FastLocalKeyInner; #[unstable(feature = "libstd_thread_internals", issue = "none")] +#[cfg(target_thread_local)] +#[cfg(test)] // when building for tests, use real std's key +pub use realstd::thread::__FastLocalKeyInner; + +#[unstable(feature = "libstd_thread_internals", issue = "none")] +#[cfg(target_thread_local)] +#[cfg(test)] +pub use self::local::fast::Key as __FastLocalKeyInnerUnused; // we import this anyway to silence 'unused' warnings + +#[unstable(feature = "libstd_thread_internals", issue = "none")] #[doc(hidden)] +#[cfg(not(target_thread_local))] pub use self::local::os::Key as __OsLocalKeyInner; #[unstable(feature = "libstd_thread_internals", issue = "none")] #[cfg(all(target_family = "wasm", not(target_feature = "atomics")))] @@ -1033,24 +1042,48 @@ pub struct ThreadId(NonZeroU64); impl ThreadId { // Generate a new unique thread ID. fn new() -> ThreadId { - // It is UB to attempt to acquire this mutex reentrantly! - static GUARD: mutex::StaticMutex = mutex::StaticMutex::new(); - static mut COUNTER: u64 = 1; - - unsafe { - let guard = GUARD.lock(); - - // If we somehow use up all our bits, panic so that we're not - // covering up subtle bugs of IDs being reused. - if COUNTER == u64::MAX { - drop(guard); // in case the panic handler ends up calling `ThreadId::new()`, avoid reentrant lock acquire. - panic!("failed to generate unique thread ID: bitspace exhausted"); - } - - let id = COUNTER; - COUNTER += 1; + #[cold] + fn exhausted() -> ! { + panic!("failed to generate unique thread ID: bitspace exhausted") + } - ThreadId(NonZeroU64::new(id).unwrap()) + cfg_if::cfg_if! { + if #[cfg(target_has_atomic = "64")] { + use crate::sync::atomic::{AtomicU64, Ordering::Relaxed}; + + static COUNTER: AtomicU64 = AtomicU64::new(0); + + let mut last = COUNTER.load(Relaxed); + loop { + let Some(id) = last.checked_add(1) else { + exhausted(); + }; + + match COUNTER.compare_exchange_weak(last, id, Relaxed, Relaxed) { + Ok(_) => return ThreadId(NonZeroU64::new(id).unwrap()), + Err(id) => last = id, + } + } + } else { + use crate::sys_common::mutex::StaticMutex; + + // It is UB to attempt to acquire this mutex reentrantly! + static GUARD: StaticMutex = StaticMutex::new(); + static mut COUNTER: u64 = 0; + + unsafe { + let guard = GUARD.lock(); + + let Some(id) = COUNTER.checked_add(1) else { + drop(guard); // in case the panic handler ends up calling `ThreadId::new()`, avoid reentrant lock acquire. + exhausted(); + }; + + COUNTER = id; + drop(guard); + ThreadId(NonZeroU64::new(id).unwrap()) + } + } } } diff --git a/library/std/src/thread/tests.rs b/library/std/src/thread/tests.rs index ec68b5291..777964f04 100644 --- a/library/std/src/thread/tests.rs +++ b/library/std/src/thread/tests.rs @@ -37,6 +37,37 @@ fn test_named_thread() { .unwrap(); } +#[cfg(any( + // Note: musl didn't add pthread_getname_np until 1.2.3 + all(target_os = "linux", target_env = "gnu"), + target_os = "macos", + target_os = "ios", + target_os = "watchos" +))] +#[test] +fn test_named_thread_truncation() { + use crate::ffi::CStr; + + let long_name = crate::iter::once("test_named_thread_truncation") + .chain(crate::iter::repeat(" yada").take(100)) + .collect::<String>(); + + let result = Builder::new().name(long_name.clone()).spawn(move || { + // Rust remembers the full thread name itself. + assert_eq!(thread::current().name(), Some(long_name.as_str())); + + // But the system is limited -- make sure we successfully set a truncation. + let mut buf = vec![0u8; long_name.len() + 1]; + unsafe { + libc::pthread_getname_np(libc::pthread_self(), buf.as_mut_ptr().cast(), buf.len()); + } + let cstr = CStr::from_bytes_until_nul(&buf).unwrap(); + assert!(cstr.to_bytes().len() > 0); + assert!(long_name.as_bytes().starts_with(cstr.to_bytes())); + }); + result.unwrap().join().unwrap(); +} + #[test] #[should_panic] fn test_invalid_named_thread() { @@ -329,3 +360,22 @@ fn test_scoped_threads_nll() { let x = 42_u8; foo(&x); } + +// Regression test for https://github.com/rust-lang/rust/issues/98498. +#[test] +#[cfg(miri)] // relies on Miri's data race detector +fn scope_join_race() { + for _ in 0..100 { + let a_bool = AtomicBool::new(false); + + thread::scope(|s| { + for _ in 0..5 { + s.spawn(|| a_bool.load(Ordering::Relaxed)); + } + + for _ in 0..5 { + s.spawn(|| a_bool.load(Ordering::Relaxed)); + } + }); + } +} |