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-rw-r--r--library/std/src/thread/local.rs3
-rw-r--r--library/std/src/thread/mod.rs85
-rw-r--r--library/std/src/thread/tests.rs50
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));
+ }
+ });
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-25 19:33:00 +0000