Merge pull request #4063 from rust-lang/rustup-2024-11-28

Automatic Rustup

5 files changed, 23 insertions, 10 deletions

diff --git a/library/std/src/sync/mpmc/array.rs b/library/std/src/sync/mpmc/array.rs
index 2c8ba411f30..a467237fef1 100644
--- a/library/std/src/sync/mpmc/array.rs
+++ b/library/std/src/sync/mpmc/array.rs
@@ -346,7 +346,8 @@ impl<T> Channel<T> {
                 }
 
                 // Block the current thread.
-                let sel = cx.wait_until(deadline);
+                // SAFETY: the context belongs to the current thread.
+                let sel = unsafe { cx.wait_until(deadline) };
 
                 match sel {
                     Selected::Waiting => unreachable!(),
@@ -397,7 +398,8 @@ impl<T> Channel<T> {
                 }
 
                 // Block the current thread.
-                let sel = cx.wait_until(deadline);
+                // SAFETY: the context belongs to the current thread.
+                let sel = unsafe { cx.wait_until(deadline) };
 
                 match sel {
                     Selected::Waiting => unreachable!(),
diff --git a/library/std/src/sync/mpmc/context.rs b/library/std/src/sync/mpmc/context.rs
index 2371d32d4ea..51aa7e82e78 100644
--- a/library/std/src/sync/mpmc/context.rs
+++ b/library/std/src/sync/mpmc/context.rs
@@ -69,7 +69,7 @@ impl Context {
             inner: Arc::new(Inner {
                 select: AtomicUsize::new(Selected::Waiting.into()),
                 packet: AtomicPtr::new(ptr::null_mut()),
-                thread: thread::current(),
+                thread: thread::current_or_unnamed(),
                 thread_id: current_thread_id(),
             }),
         }
@@ -112,8 +112,11 @@ impl Context {
     /// Waits until an operation is selected and returns it.
     ///
     /// If the deadline is reached, `Selected::Aborted` will be selected.
+    ///
+    /// # Safety
+    /// This may only be called from the thread this `Context` belongs to.
     #[inline]
-    pub fn wait_until(&self, deadline: Option<Instant>) -> Selected {
+    pub unsafe fn wait_until(&self, deadline: Option<Instant>) -> Selected {
         loop {
             // Check whether an operation has been selected.
             let sel = Selected::from(self.inner.select.load(Ordering::Acquire));
@@ -126,7 +129,8 @@ impl Context {
                 let now = Instant::now();
 
                 if now < end {
-                    thread::park_timeout(end - now);
+                    // SAFETY: guaranteed by caller.
+                    unsafe { self.inner.thread.park_timeout(end - now) };
                 } else {
                     // The deadline has been reached. Try aborting select.
                     return match self.try_select(Selected::Aborted) {
@@ -135,7 +139,8 @@ impl Context {
                     };
                 }
             } else {
-                thread::park();
+                // SAFETY: guaranteed by caller.
+                unsafe { self.inner.thread.park() };
             }
         }
     }
diff --git a/library/std/src/sync/mpmc/list.rs b/library/std/src/sync/mpmc/list.rs
index 523e6d2f3bb..d88914f5291 100644
--- a/library/std/src/sync/mpmc/list.rs
+++ b/library/std/src/sync/mpmc/list.rs
@@ -444,7 +444,8 @@ impl<T> Channel<T> {
                 }
 
                 // Block the current thread.
-                let sel = cx.wait_until(deadline);
+                // SAFETY: the context belongs to the current thread.
+                let sel = unsafe { cx.wait_until(deadline) };
 
                 match sel {
                     Selected::Waiting => unreachable!(),
diff --git a/library/std/src/sync/mpmc/zero.rs b/library/std/src/sync/mpmc/zero.rs
index 446881291e6..577997c07a6 100644
--- a/library/std/src/sync/mpmc/zero.rs
+++ b/library/std/src/sync/mpmc/zero.rs
@@ -190,7 +190,8 @@ impl<T> Channel<T> {
             drop(inner);
 
             // Block the current thread.
-            let sel = cx.wait_until(deadline);
+            // SAFETY: the context belongs to the current thread.
+            let sel = unsafe { cx.wait_until(deadline) };
 
             match sel {
                 Selected::Waiting => unreachable!(),
@@ -257,7 +258,8 @@ impl<T> Channel<T> {
             drop(inner);
 
             // Block the current thread.
-            let sel = cx.wait_until(deadline);
+            // SAFETY: the context belongs to the current thread.
+            let sel = unsafe { cx.wait_until(deadline) };
 
             match sel {
                 Selected::Waiting => unreachable!(),
diff --git a/library/std/src/sync/rwlock/tests.rs b/library/std/src/sync/rwlock/tests.rs
index 29cad4400f1..48d442921f7 100644
--- a/library/std/src/sync/rwlock/tests.rs
+++ b/library/std/src/sync/rwlock/tests.rs
@@ -511,12 +511,15 @@ fn test_downgrade_basic() {
 }
 
 #[test]
+// FIXME: On macOS we use a provenance-incorrect implementation and Miri catches that issue.
+// See <https://github.com/rust-lang/rust/issues/121950> for details.
+#[cfg_attr(all(miri, target_os = "macos"), ignore)]
 fn test_downgrade_observe() {
     // Taken from the test `test_rwlock_downgrade` from:
     // https://github.com/Amanieu/parking_lot/blob/master/src/rwlock.rs
 
     const W: usize = 20;
-    const N: usize = 100;
+    const N: usize = if cfg!(miri) { 40 } else { 100 };
 
     // This test spawns `W` writer threads, where each will increment a counter `N` times, ensuring
     // that the value they wrote has not changed after downgrading.