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-rw-r--r--src/libstd/io/stdio.rs49
-rw-r--r--src/libstd/sys/cloudabi/mutex.rs8
-rw-r--r--src/libstd/sys/hermit/mutex.rs6
-rw-r--r--src/libstd/sys/sgx/mutex.rs2
-rw-r--r--src/libstd/sys/unix/mutex.rs4
-rw-r--r--src/libstd/sys/vxworks/mutex.rs4
-rw-r--r--src/libstd/sys/wasm/mutex.rs4
-rw-r--r--src/libstd/sys/wasm/mutex_atomics.rs4
-rw-r--r--src/libstd/sys/windows/mutex.rs6
-rw-r--r--src/libstd/sys_common/remutex.rs114
10 files changed, 101 insertions, 100 deletions
diff --git a/src/libstd/io/stdio.rs b/src/libstd/io/stdio.rs
index d410faca30d..0ac92881718 100644
--- a/src/libstd/io/stdio.rs
+++ b/src/libstd/io/stdio.rs
@@ -6,7 +6,7 @@ use crate::cell::RefCell;
 use crate::fmt;
 use crate::io::lazy::Lazy;
 use crate::io::{self, BufReader, Initializer, IoSlice, IoSliceMut, LineWriter};
-use crate::sync::{Arc, Mutex, MutexGuard};
+use crate::sync::{Arc, Mutex, MutexGuard, Once};
 use crate::sys::stdio;
 use crate::sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
 use crate::thread::LocalKey;
@@ -493,7 +493,11 @@ pub fn stdout() -> Stdout {
             Ok(stdout) => Maybe::Real(stdout),
             _ => Maybe::Fake,
         };
-        Arc::new(ReentrantMutex::new(RefCell::new(LineWriter::new(stdout))))
+        unsafe {
+            let ret = Arc::new(ReentrantMutex::new(RefCell::new(LineWriter::new(stdout))));
+            ret.init();
+            return ret;
+        }
     }
 }
 
@@ -520,7 +524,7 @@ impl Stdout {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn lock(&self) -> StdoutLock<'_> {
-        StdoutLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
+        StdoutLock { inner: self.inner.lock() }
     }
 }
 
@@ -581,7 +585,7 @@ impl fmt::Debug for StdoutLock<'_> {
 /// an error.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Stderr {
-    inner: Arc<ReentrantMutex<RefCell<Maybe<StderrRaw>>>>,
+    inner: &'static ReentrantMutex<RefCell<Maybe<StderrRaw>>>,
 }
 
 /// A locked reference to the `Stderr` handle.
@@ -639,19 +643,28 @@ pub struct StderrLock<'a> {
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn stderr() -> Stderr {
-    static INSTANCE: Lazy<ReentrantMutex<RefCell<Maybe<StderrRaw>>>> = Lazy::new();
-    return Stderr {
-        inner: unsafe { INSTANCE.get(stderr_init).expect("cannot access stderr during shutdown") },
-    };
-
-    fn stderr_init() -> Arc<ReentrantMutex<RefCell<Maybe<StderrRaw>>>> {
-        // This must not reentrantly access `INSTANCE`
-        let stderr = match stderr_raw() {
-            Ok(stderr) => Maybe::Real(stderr),
-            _ => Maybe::Fake,
-        };
-        Arc::new(ReentrantMutex::new(RefCell::new(stderr)))
-    }
+    // Note that unlike `stdout()` we don't use `Lazy` here which registers a
+    // destructor. Stderr is not buffered nor does the `stderr_raw` type consume
+    // any owned resources, so there's no need to run any destructors at some
+    // point in the future.
+    //
+    // This has the added benefit of allowing `stderr` to be usable during
+    // process shutdown as well!
+    static INSTANCE: ReentrantMutex<RefCell<Maybe<StderrRaw>>> =
+        unsafe { ReentrantMutex::new(RefCell::new(Maybe::Fake)) };
+
+    // When accessing stderr we need one-time initialization of the reentrant
+    // mutex, followed by one-time detection of whether we actually have a
+    // stderr handle or not. Afterwards we can just always use the now-filled-in
+    // `INSTANCE` value.
+    static INIT: Once = Once::new();
+    INIT.call_once(|| unsafe {
+        INSTANCE.init();
+        if let Ok(stderr) = stderr_raw() {
+            *INSTANCE.lock().borrow_mut() = Maybe::Real(stderr);
+        }
+    });
+    return Stderr { inner: &INSTANCE };
 }
 
 impl Stderr {
@@ -677,7 +690,7 @@ impl Stderr {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn lock(&self) -> StderrLock<'_> {
-        StderrLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
+        StderrLock { inner: self.inner.lock() }
     }
 }
 
diff --git a/src/libstd/sys/cloudabi/mutex.rs b/src/libstd/sys/cloudabi/mutex.rs
index 4aa25e25052..580ab0e8ad8 100644
--- a/src/libstd/sys/cloudabi/mutex.rs
+++ b/src/libstd/sys/cloudabi/mutex.rs
@@ -53,16 +53,16 @@ pub struct ReentrantMutex {
 }
 
 impl ReentrantMutex {
-    pub unsafe fn uninitialized() -> ReentrantMutex {
+    pub const unsafe fn uninitialized() -> ReentrantMutex {
         ReentrantMutex {
             lock: UnsafeCell::new(MaybeUninit::uninit()),
             recursion: UnsafeCell::new(MaybeUninit::uninit()),
         }
     }
 
-    pub unsafe fn init(&mut self) {
-        self.lock = UnsafeCell::new(MaybeUninit::new(AtomicU32::new(abi::LOCK_UNLOCKED.0)));
-        self.recursion = UnsafeCell::new(MaybeUninit::new(0));
+    pub unsafe fn init(&self) {
+        *self.lock.get() = MaybeUninit::new(AtomicU32::new(abi::LOCK_UNLOCKED.0));
+        *self.recursion.get() = MaybeUninit::new(0);
     }
 
     pub unsafe fn try_lock(&self) -> bool {
diff --git a/src/libstd/sys/hermit/mutex.rs b/src/libstd/sys/hermit/mutex.rs
index b5c75f738d2..3d4813209cb 100644
--- a/src/libstd/sys/hermit/mutex.rs
+++ b/src/libstd/sys/hermit/mutex.rs
@@ -46,13 +46,13 @@ pub struct ReentrantMutex {
 }
 
 impl ReentrantMutex {
-    pub unsafe fn uninitialized() -> ReentrantMutex {
+    pub const unsafe fn uninitialized() -> ReentrantMutex {
         ReentrantMutex { inner: ptr::null() }
     }
 
     #[inline]
-    pub unsafe fn init(&mut self) {
-        let _ = abi::recmutex_init(&mut self.inner as *mut *const c_void);
+    pub unsafe fn init(&self) {
+        let _ = abi::recmutex_init(&self.inner as *const *const c_void as *mut _);
     }
 
     #[inline]
diff --git a/src/libstd/sys/sgx/mutex.rs b/src/libstd/sys/sgx/mutex.rs
index eebbea1b285..4911c2f5387 100644
--- a/src/libstd/sys/sgx/mutex.rs
+++ b/src/libstd/sys/sgx/mutex.rs
@@ -75,7 +75,7 @@ impl ReentrantMutex {
     }
 
     #[inline]
-    pub unsafe fn init(&mut self) {}
+    pub unsafe fn init(&self) {}
 
     #[inline]
     pub unsafe fn lock(&self) {
diff --git a/src/libstd/sys/unix/mutex.rs b/src/libstd/sys/unix/mutex.rs
index b38375a2e03..103d87e3d2f 100644
--- a/src/libstd/sys/unix/mutex.rs
+++ b/src/libstd/sys/unix/mutex.rs
@@ -92,11 +92,11 @@ unsafe impl Send for ReentrantMutex {}
 unsafe impl Sync for ReentrantMutex {}
 
 impl ReentrantMutex {
-    pub unsafe fn uninitialized() -> ReentrantMutex {
+    pub const unsafe fn uninitialized() -> ReentrantMutex {
         ReentrantMutex { inner: UnsafeCell::new(libc::PTHREAD_MUTEX_INITIALIZER) }
     }
 
-    pub unsafe fn init(&mut self) {
+    pub unsafe fn init(&self) {
         let mut attr = MaybeUninit::<libc::pthread_mutexattr_t>::uninit();
         let result = libc::pthread_mutexattr_init(attr.as_mut_ptr());
         debug_assert_eq!(result, 0);
diff --git a/src/libstd/sys/vxworks/mutex.rs b/src/libstd/sys/vxworks/mutex.rs
index b38375a2e03..103d87e3d2f 100644
--- a/src/libstd/sys/vxworks/mutex.rs
+++ b/src/libstd/sys/vxworks/mutex.rs
@@ -92,11 +92,11 @@ unsafe impl Send for ReentrantMutex {}
 unsafe impl Sync for ReentrantMutex {}
 
 impl ReentrantMutex {
-    pub unsafe fn uninitialized() -> ReentrantMutex {
+    pub const unsafe fn uninitialized() -> ReentrantMutex {
         ReentrantMutex { inner: UnsafeCell::new(libc::PTHREAD_MUTEX_INITIALIZER) }
     }
 
-    pub unsafe fn init(&mut self) {
+    pub unsafe fn init(&self) {
         let mut attr = MaybeUninit::<libc::pthread_mutexattr_t>::uninit();
         let result = libc::pthread_mutexattr_init(attr.as_mut_ptr());
         debug_assert_eq!(result, 0);
diff --git a/src/libstd/sys/wasm/mutex.rs b/src/libstd/sys/wasm/mutex.rs
index 07238d08730..7aaf1b3a343 100644
--- a/src/libstd/sys/wasm/mutex.rs
+++ b/src/libstd/sys/wasm/mutex.rs
@@ -47,11 +47,11 @@ impl Mutex {
 pub struct ReentrantMutex {}
 
 impl ReentrantMutex {
-    pub unsafe fn uninitialized() -> ReentrantMutex {
+    pub const unsafe fn uninitialized() -> ReentrantMutex {
         ReentrantMutex {}
     }
 
-    pub unsafe fn init(&mut self) {}
+    pub unsafe fn init(&self) {}
 
     pub unsafe fn lock(&self) {}
 
diff --git a/src/libstd/sys/wasm/mutex_atomics.rs b/src/libstd/sys/wasm/mutex_atomics.rs
index 90c628a19c2..268a53bb564 100644
--- a/src/libstd/sys/wasm/mutex_atomics.rs
+++ b/src/libstd/sys/wasm/mutex_atomics.rs
@@ -80,11 +80,11 @@ unsafe impl Sync for ReentrantMutex {}
 // released when this recursion counter reaches 0.
 
 impl ReentrantMutex {
-    pub unsafe fn uninitialized() -> ReentrantMutex {
+    pub const unsafe fn uninitialized() -> ReentrantMutex {
         ReentrantMutex { owner: AtomicU32::new(0), recursions: UnsafeCell::new(0) }
     }
 
-    pub unsafe fn init(&mut self) {
+    pub unsafe fn init(&self) {
         // nothing to do...
     }
 
diff --git a/src/libstd/sys/windows/mutex.rs b/src/libstd/sys/windows/mutex.rs
index 281eb294c65..63dfc640908 100644
--- a/src/libstd/sys/windows/mutex.rs
+++ b/src/libstd/sys/windows/mutex.rs
@@ -109,7 +109,7 @@ impl Mutex {
             0 => {}
             n => return n as *mut _,
         }
-        let mut re = box ReentrantMutex::uninitialized();
+        let re = box ReentrantMutex::uninitialized();
         re.init();
         let re = Box::into_raw(re);
         match self.lock.compare_and_swap(0, re as usize, Ordering::SeqCst) {
@@ -157,11 +157,11 @@ unsafe impl Send for ReentrantMutex {}
 unsafe impl Sync for ReentrantMutex {}
 
 impl ReentrantMutex {
-    pub fn uninitialized() -> ReentrantMutex {
+    pub const fn uninitialized() -> ReentrantMutex {
         ReentrantMutex { inner: UnsafeCell::new(MaybeUninit::uninit()) }
     }
 
-    pub unsafe fn init(&mut self) {
+    pub unsafe fn init(&self) {
         c::InitializeCriticalSection((&mut *self.inner.get()).as_mut_ptr());
     }
 
diff --git a/src/libstd/sys_common/remutex.rs b/src/libstd/sys_common/remutex.rs
index a1ad44a3666..4f19bbc467f 100644
--- a/src/libstd/sys_common/remutex.rs
+++ b/src/libstd/sys_common/remutex.rs
@@ -3,7 +3,6 @@ use crate::marker;
 use crate::ops::Deref;
 use crate::panic::{RefUnwindSafe, UnwindSafe};
 use crate::sys::mutex as sys;
-use crate::sys_common::poison::{self, LockResult, TryLockError, TryLockResult};
 
 /// A re-entrant mutual exclusion
 ///
@@ -11,8 +10,7 @@ use crate::sys_common::poison::{self, LockResult, TryLockError, TryLockResult};
 /// available. The thread which has already locked the mutex can lock it
 /// multiple times without blocking, preventing a common source of deadlocks.
 pub struct ReentrantMutex<T> {
-    inner: Box<sys::ReentrantMutex>,
-    poison: poison::Flag,
+    inner: sys::ReentrantMutex,
     data: T,
 }
 
@@ -39,23 +37,30 @@ pub struct ReentrantMutexGuard<'a, T: 'a> {
     // funny underscores due to how Deref currently works (it disregards field
     // privacy).
     __lock: &'a ReentrantMutex<T>,
-    __poison: poison::Guard,
 }
 
 impl<T> !marker::Send for ReentrantMutexGuard<'_, T> {}
 
 impl<T> ReentrantMutex<T> {
     /// Creates a new reentrant mutex in an unlocked state.
-    pub fn new(t: T) -> ReentrantMutex<T> {
-        unsafe {
-            let mut mutex = ReentrantMutex {
-                inner: box sys::ReentrantMutex::uninitialized(),
-                poison: poison::Flag::new(),
-                data: t,
-            };
-            mutex.inner.init();
-            mutex
-        }
+    ///
+    /// # Unsafety
+    ///
+    /// This function is unsafe because it is required that `init` is called
+    /// once this mutex is in its final resting place, and only then are the
+    /// lock/unlock methods safe.
+    pub const unsafe fn new(t: T) -> ReentrantMutex<T> {
+        ReentrantMutex { inner: sys::ReentrantMutex::uninitialized(), data: t }
+    }
+
+    /// Initializes this mutex so it's ready for use.
+    ///
+    /// # Unsafety
+    ///
+    /// Unsafe to call more than once, and must be called after this will no
+    /// longer move in memory.
+    pub unsafe fn init(&self) {
+        self.inner.init();
     }
 
     /// Acquires a mutex, blocking the current thread until it is able to do so.
@@ -70,7 +75,7 @@ impl<T> ReentrantMutex<T> {
     /// If another user of this mutex panicked while holding the mutex, then
     /// this call will return failure if the mutex would otherwise be
     /// acquired.
-    pub fn lock(&self) -> LockResult<ReentrantMutexGuard<'_, T>> {
+    pub fn lock(&self) -> ReentrantMutexGuard<'_, T> {
         unsafe { self.inner.lock() }
         ReentrantMutexGuard::new(&self)
     }
@@ -87,12 +92,8 @@ impl<T> ReentrantMutex<T> {
     /// If another user of this mutex panicked while holding the mutex, then
     /// this call will return failure if the mutex would otherwise be
     /// acquired.
-    pub fn try_lock(&self) -> TryLockResult<ReentrantMutexGuard<'_, T>> {
-        if unsafe { self.inner.try_lock() } {
-            Ok(ReentrantMutexGuard::new(&self)?)
-        } else {
-            Err(TryLockError::WouldBlock)
-        }
+    pub fn try_lock(&self) -> Option<ReentrantMutexGuard<'_, T>> {
+        if unsafe { self.inner.try_lock() } { Some(ReentrantMutexGuard::new(&self)) } else { None }
     }
 }
 
@@ -108,11 +109,8 @@ impl<T> Drop for ReentrantMutex<T> {
 impl<T: fmt::Debug + 'static> fmt::Debug for ReentrantMutex<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self.try_lock() {
-            Ok(guard) => f.debug_struct("ReentrantMutex").field("data", &*guard).finish(),
-            Err(TryLockError::Poisoned(err)) => {
-                f.debug_struct("ReentrantMutex").field("data", &**err.get_ref()).finish()
-            }
-            Err(TryLockError::WouldBlock) => {
+            Some(guard) => f.debug_struct("ReentrantMutex").field("data", &*guard).finish(),
+            None => {
                 struct LockedPlaceholder;
                 impl fmt::Debug for LockedPlaceholder {
                     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -127,11 +125,8 @@ impl<T: fmt::Debug + 'static> fmt::Debug for ReentrantMutex<T> {
 }
 
 impl<'mutex, T> ReentrantMutexGuard<'mutex, T> {
-    fn new(lock: &'mutex ReentrantMutex<T>) -> LockResult<ReentrantMutexGuard<'mutex, T>> {
-        poison::map_result(lock.poison.borrow(), |guard| ReentrantMutexGuard {
-            __lock: lock,
-            __poison: guard,
-        })
+    fn new(lock: &'mutex ReentrantMutex<T>) -> ReentrantMutexGuard<'mutex, T> {
+        ReentrantMutexGuard { __lock: lock }
     }
 }
 
@@ -147,7 +142,6 @@ impl<T> Drop for ReentrantMutexGuard<'_, T> {
     #[inline]
     fn drop(&mut self) {
         unsafe {
-            self.__lock.poison.done(&self.__poison);
             self.__lock.inner.unlock();
         }
     }
@@ -162,13 +156,17 @@ mod tests {
 
     #[test]
     fn smoke() {
-        let m = ReentrantMutex::new(());
+        let m = unsafe {
+            let m = ReentrantMutex::new(());
+            m.init();
+            m
+        };
         {
-            let a = m.lock().unwrap();
+            let a = m.lock();
             {
-                let b = m.lock().unwrap();
+                let b = m.lock();
                 {
-                    let c = m.lock().unwrap();
+                    let c = m.lock();
                     assert_eq!(*c, ());
                 }
                 assert_eq!(*b, ());
@@ -179,15 +177,19 @@ mod tests {
 
     #[test]
     fn is_mutex() {
-        let m = Arc::new(ReentrantMutex::new(RefCell::new(0)));
+        let m = unsafe {
+            let m = Arc::new(ReentrantMutex::new(RefCell::new(0)));
+            m.init();
+            m
+        };
         let m2 = m.clone();
-        let lock = m.lock().unwrap();
+        let lock = m.lock();
         let child = thread::spawn(move || {
-            let lock = m2.lock().unwrap();
+            let lock = m2.lock();
             assert_eq!(*lock.borrow(), 4950);
         });
         for i in 0..100 {
-            let lock = m.lock().unwrap();
+            let lock = m.lock();
             *lock.borrow_mut() += i;
         }
         drop(lock);
@@ -196,17 +198,21 @@ mod tests {
 
     #[test]
     fn trylock_works() {
-        let m = Arc::new(ReentrantMutex::new(()));
+        let m = unsafe {
+            let m = Arc::new(ReentrantMutex::new(()));
+            m.init();
+            m
+        };
         let m2 = m.clone();
-        let _lock = m.try_lock().unwrap();
-        let _lock2 = m.try_lock().unwrap();
+        let _lock = m.try_lock();
+        let _lock2 = m.try_lock();
         thread::spawn(move || {
             let lock = m2.try_lock();
-            assert!(lock.is_err());
+            assert!(lock.is_none());
         })
         .join()
         .unwrap();
-        let _lock3 = m.try_lock().unwrap();
+        let _lock3 = m.try_lock();
     }
 
     pub struct Answer<'a>(pub ReentrantMutexGuard<'a, RefCell<u32>>);
@@ -215,22 +221,4 @@ mod tests {
             *self.0.borrow_mut() = 42;
         }
     }
-
-    #[test]
-    fn poison_works() {
-        let m = Arc::new(ReentrantMutex::new(RefCell::new(0)));
-        let mc = m.clone();
-        let result = thread::spawn(move || {
-            let lock = mc.lock().unwrap();
-            *lock.borrow_mut() = 1;
-            let lock2 = mc.lock().unwrap();
-            *lock.borrow_mut() = 2;
-            let _answer = Answer(lock2);
-            panic!("What the answer to my lifetimes dilemma is?");
-        })
-        .join();
-        assert!(result.is_err());
-        let r = m.lock().err().unwrap().into_inner();
-        assert_eq!(*r.borrow(), 42);
-    }
 }
generated by cgit-pink 1.4.1-3-g733a5 (git 2.37.1) at 2026-07-15 20:15:17 +0000