diff --git a/library/std/src/sync/reentrant_lock.rs b/library/std/src/sync/reentrant_lock.rs index 24539d4e8303d..96a4cf12659cc 100644 --- a/library/std/src/sync/reentrant_lock.rs +++ b/library/std/src/sync/reentrant_lock.rs @@ -136,7 +136,7 @@ cfg_if!( // we only ever read from the tid if `tls_addr` matches the current // TLS address. In that case, either the tid has been set by // the current thread, or by a thread that has terminated before - // the current thread was created. In either case, no further + // the current thread's `tls_addr` was allocated. In either case, no further // synchronization is needed (as per ) tls_addr: Atomic, tid: UnsafeCell, @@ -154,8 +154,12 @@ cfg_if!( // NOTE: This assumes that `owner` is the ID of the current // thread, and may spuriously return `false` if that's not the case. fn contains(&self, owner: ThreadId) -> bool { + // We must call `tls_addr()` *before* doing the load to ensure that if we reuse an + // earlier thread's address, the `tls_addr.load()` below happens-after everything + // that thread did. + let tls_addr = tls_addr(); // SAFETY: See the comments in the struct definition. - self.tls_addr.load(Ordering::Relaxed) == tls_addr() + self.tls_addr.load(Ordering::Relaxed) == tls_addr && unsafe { *self.tid.get() } == owner.as_u64().get() } diff --git a/src/tools/miri/README.md b/src/tools/miri/README.md index b692ddab4ffc8..122438a2509b3 100644 --- a/src/tools/miri/README.md +++ b/src/tools/miri/README.md @@ -580,6 +580,7 @@ Definite bugs found: * [Weak-memory-induced memory leak in Windows thread-local storage](https://github.com/rust-lang/rust/pull/124281) * [A bug in the new `RwLock::downgrade` implementation](https://rust-lang.zulipchat.com/#narrow/channel/269128-miri/topic/Miri.20error.20library.20test) (caught by Miri before it landed in the Rust repo) * [Mockall reading unintialized memory when mocking `std::io::Read::read`, even if all expectations are satisfied](https://github.com/asomers/mockall/issues/647) (caught by Miri running Tokio's test suite) +* [`ReentrantLock` not correctly dealing with reuse of addresses for TLS storage of different threads](https://github.com/rust-lang/rust/pull/141248) Violations of [Stacked Borrows] found that are likely bugs (but Stacked Borrows is currently just an experiment): diff --git a/src/tools/miri/tests/many-seeds/reentrant-lock.rs b/src/tools/miri/tests/many-seeds/reentrant-lock.rs new file mode 100644 index 0000000000000..8a363179a9cc7 --- /dev/null +++ b/src/tools/miri/tests/many-seeds/reentrant-lock.rs @@ -0,0 +1,19 @@ +#![feature(reentrant_lock)] +//! This is a regression test for +//! . + +use std::cell::Cell; +use std::sync::ReentrantLock; +use std::thread; + +static LOCK: ReentrantLock> = ReentrantLock::new(Cell::new(0)); + +fn main() { + for _ in 0..20 { + thread::spawn(move || { + let val = LOCK.lock(); + val.set(val.get() + 1); + drop(val); + }); + } +}