Move `sys_common::poison` to `sync::poison`

5 files changed, 265 insertions, 6 deletions

diff --git a/library/std/src/sync/condvar.rs b/library/std/src/sync/condvar.rs
index 60be63c9543..2f0b32c90d0 100644
--- a/library/std/src/sync/condvar.rs
+++ b/library/std/src/sync/condvar.rs
@@ -2,9 +2,8 @@
 mod tests;
 
 use crate::fmt;
-use crate::sync::{mutex, MutexGuard, PoisonError};
+use crate::sync::{mutex, poison, LockResult, MutexGuard, PoisonError};
 use crate::sys_common::condvar as sys;
-use crate::sys_common::poison::{self, LockResult};
 use crate::time::{Duration, Instant};
 
 /// A type indicating whether a timed wait on a condition variable returned
diff --git a/library/std/src/sync/mod.rs b/library/std/src/sync/mod.rs
index b6699910b07..ee35598bab5 100644
--- a/library/std/src/sync/mod.rs
+++ b/library/std/src/sync/mod.rs
@@ -166,9 +166,9 @@ pub use self::mutex::{Mutex, MutexGuard};
 #[allow(deprecated)]
 pub use self::once::{Once, OnceState, ONCE_INIT};
 #[stable(feature = "rust1", since = "1.0.0")]
-pub use self::rwlock::{RwLock, RwLockReadGuard, RwLockWriteGuard};
+pub use self::poison::{LockResult, PoisonError, TryLockError, TryLockResult};
 #[stable(feature = "rust1", since = "1.0.0")]
-pub use crate::sys_common::poison::{LockResult, PoisonError, TryLockError, TryLockResult};
+pub use self::rwlock::{RwLock, RwLockReadGuard, RwLockWriteGuard};
 
 pub mod mpsc;
 
@@ -176,4 +176,5 @@ mod barrier;
 mod condvar;
 mod mutex;
 mod once;
+mod poison;
 mod rwlock;
diff --git a/library/std/src/sync/mutex.rs b/library/std/src/sync/mutex.rs
index 98c34282e0c..2615bea6592 100644
--- a/library/std/src/sync/mutex.rs
+++ b/library/std/src/sync/mutex.rs
@@ -6,8 +6,8 @@ use crate::fmt;
 use crate::mem;
 use crate::ops::{Deref, DerefMut};
 use crate::ptr;
+use crate::sync::{poison, LockResult, TryLockError, TryLockResult};
 use crate::sys_common::mutex as sys;
-use crate::sys_common::poison::{self, LockResult, TryLockError, TryLockResult};
 
 /// A mutual exclusion primitive useful for protecting shared data
 ///
diff --git a/library/std/src/sync/poison.rs b/library/std/src/sync/poison.rs
new file mode 100644
index 00000000000..05e1833c3e5
--- /dev/null
+++ b/library/std/src/sync/poison.rs
@@ -0,0 +1,259 @@
+use crate::error::Error;
+use crate::fmt;
+use crate::sync::atomic::{AtomicBool, Ordering};
+use crate::thread;
+
+pub struct Flag {
+    failed: AtomicBool,
+}
+
+// Note that the Ordering uses to access the `failed` field of `Flag` below is
+// always `Relaxed`, and that's because this isn't actually protecting any data,
+// it's just a flag whether we've panicked or not.
+//
+// The actual location that this matters is when a mutex is **locked** which is
+// where we have external synchronization ensuring that we see memory
+// reads/writes to this flag.
+//
+// As a result, if it matters, we should see the correct value for `failed` in
+// all cases.
+
+impl Flag {
+    pub const fn new() -> Flag {
+        Flag { failed: AtomicBool::new(false) }
+    }
+
+    #[inline]
+    pub fn borrow(&self) -> LockResult<Guard> {
+        let ret = Guard { panicking: thread::panicking() };
+        if self.get() { Err(PoisonError::new(ret)) } else { Ok(ret) }
+    }
+
+    #[inline]
+    pub fn done(&self, guard: &Guard) {
+        if !guard.panicking && thread::panicking() {
+            self.failed.store(true, Ordering::Relaxed);
+        }
+    }
+
+    #[inline]
+    pub fn get(&self) -> bool {
+        self.failed.load(Ordering::Relaxed)
+    }
+}
+
+pub struct Guard {
+    panicking: bool,
+}
+
+/// A type of error which can be returned whenever a lock is acquired.
+///
+/// Both [`Mutex`]es and [`RwLock`]s are poisoned whenever a thread fails while the lock
+/// is held. The precise semantics for when a lock is poisoned is documented on
+/// each lock, but once a lock is poisoned then all future acquisitions will
+/// return this error.
+///
+/// # Examples
+///
+/// ```
+/// use std::sync::{Arc, Mutex};
+/// use std::thread;
+///
+/// let mutex = Arc::new(Mutex::new(1));
+///
+/// // poison the mutex
+/// let c_mutex = Arc::clone(&mutex);
+/// let _ = thread::spawn(move || {
+///     let mut data = c_mutex.lock().unwrap();
+///     *data = 2;
+///     panic!();
+/// }).join();
+///
+/// match mutex.lock() {
+///     Ok(_) => unreachable!(),
+///     Err(p_err) => {
+///         let data = p_err.get_ref();
+///         println!("recovered: {}", data);
+///     }
+/// };
+/// ```
+/// [`Mutex`]: crate::sync::Mutex
+/// [`RwLock`]: crate::sync::RwLock
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct PoisonError<T> {
+    guard: T,
+}
+
+/// An enumeration of possible errors associated with a [`TryLockResult`] which
+/// can occur while trying to acquire a lock, from the [`try_lock`] method on a
+/// [`Mutex`] or the [`try_read`] and [`try_write`] methods on an [`RwLock`].
+///
+/// [`try_lock`]: crate::sync::Mutex::try_lock
+/// [`try_read`]: crate::sync::RwLock::try_read
+/// [`try_write`]: crate::sync::RwLock::try_write
+/// [`Mutex`]: crate::sync::Mutex
+/// [`RwLock`]: crate::sync::RwLock
+#[stable(feature = "rust1", since = "1.0.0")]
+pub enum TryLockError<T> {
+    /// The lock could not be acquired because another thread failed while holding
+    /// the lock.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    Poisoned(#[stable(feature = "rust1", since = "1.0.0")] PoisonError<T>),
+    /// The lock could not be acquired at this time because the operation would
+    /// otherwise block.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    WouldBlock,
+}
+
+/// A type alias for the result of a lock method which can be poisoned.
+///
+/// The [`Ok`] variant of this result indicates that the primitive was not
+/// poisoned, and the `Guard` is contained within. The [`Err`] variant indicates
+/// that the primitive was poisoned. Note that the [`Err`] variant *also* carries
+/// the associated guard, and it can be acquired through the [`into_inner`]
+/// method.
+///
+/// [`into_inner`]: PoisonError::into_inner
+#[stable(feature = "rust1", since = "1.0.0")]
+pub type LockResult<Guard> = Result<Guard, PoisonError<Guard>>;
+
+/// A type alias for the result of a nonblocking locking method.
+///
+/// For more information, see [`LockResult`]. A `TryLockResult` doesn't
+/// necessarily hold the associated guard in the [`Err`] type as the lock may not
+/// have been acquired for other reasons.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub type TryLockResult<Guard> = Result<Guard, TryLockError<Guard>>;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> fmt::Debug for PoisonError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("PoisonError").finish_non_exhaustive()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> fmt::Display for PoisonError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "poisoned lock: another task failed inside".fmt(f)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> Error for PoisonError<T> {
+    #[allow(deprecated)]
+    fn description(&self) -> &str {
+        "poisoned lock: another task failed inside"
+    }
+}
+
+impl<T> PoisonError<T> {
+    /// Creates a `PoisonError`.
+    ///
+    /// This is generally created by methods like [`Mutex::lock`](crate::sync::Mutex::lock)
+    /// or [`RwLock::read`](crate::sync::RwLock::read).
+    #[stable(feature = "sync_poison", since = "1.2.0")]
+    pub fn new(guard: T) -> PoisonError<T> {
+        PoisonError { guard }
+    }
+
+    /// Consumes this error indicating that a lock is poisoned, returning the
+    /// underlying guard to allow access regardless.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::HashSet;
+    /// use std::sync::{Arc, Mutex};
+    /// use std::thread;
+    ///
+    /// let mutex = Arc::new(Mutex::new(HashSet::new()));
+    ///
+    /// // poison the mutex
+    /// let c_mutex = Arc::clone(&mutex);
+    /// let _ = thread::spawn(move || {
+    ///     let mut data = c_mutex.lock().unwrap();
+    ///     data.insert(10);
+    ///     panic!();
+    /// }).join();
+    ///
+    /// let p_err = mutex.lock().unwrap_err();
+    /// let data = p_err.into_inner();
+    /// println!("recovered {} items", data.len());
+    /// ```
+    #[stable(feature = "sync_poison", since = "1.2.0")]
+    pub fn into_inner(self) -> T {
+        self.guard
+    }
+
+    /// Reaches into this error indicating that a lock is poisoned, returning a
+    /// reference to the underlying guard to allow access regardless.
+    #[stable(feature = "sync_poison", since = "1.2.0")]
+    pub fn get_ref(&self) -> &T {
+        &self.guard
+    }
+
+    /// Reaches into this error indicating that a lock is poisoned, returning a
+    /// mutable reference to the underlying guard to allow access regardless.
+    #[stable(feature = "sync_poison", since = "1.2.0")]
+    pub fn get_mut(&mut self) -> &mut T {
+        &mut self.guard
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> From<PoisonError<T>> for TryLockError<T> {
+    fn from(err: PoisonError<T>) -> TryLockError<T> {
+        TryLockError::Poisoned(err)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> fmt::Debug for TryLockError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            TryLockError::Poisoned(..) => "Poisoned(..)".fmt(f),
+            TryLockError::WouldBlock => "WouldBlock".fmt(f),
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> fmt::Display for TryLockError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            TryLockError::Poisoned(..) => "poisoned lock: another task failed inside",
+            TryLockError::WouldBlock => "try_lock failed because the operation would block",
+        }
+        .fmt(f)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> Error for TryLockError<T> {
+    #[allow(deprecated, deprecated_in_future)]
+    fn description(&self) -> &str {
+        match *self {
+            TryLockError::Poisoned(ref p) => p.description(),
+            TryLockError::WouldBlock => "try_lock failed because the operation would block",
+        }
+    }
+
+    #[allow(deprecated)]
+    fn cause(&self) -> Option<&dyn Error> {
+        match *self {
+            TryLockError::Poisoned(ref p) => Some(p),
+            _ => None,
+        }
+    }
+}
+
+pub fn map_result<T, U, F>(result: LockResult<T>, f: F) -> LockResult<U>
+where
+    F: FnOnce(T) -> U,
+{
+    match result {
+        Ok(t) => Ok(f(t)),
+        Err(PoisonError { guard }) => Err(PoisonError::new(f(guard))),
+    }
+}
diff --git a/library/std/src/sync/rwlock.rs b/library/std/src/sync/rwlock.rs
index 351804ec979..b01bcec1361 100644
--- a/library/std/src/sync/rwlock.rs
+++ b/library/std/src/sync/rwlock.rs
@@ -6,7 +6,7 @@ use crate::fmt;
 use crate::mem;
 use crate::ops::{Deref, DerefMut};
 use crate::ptr;
-use crate::sys_common::poison::{self, LockResult, TryLockError, TryLockResult};
+use crate::sync::{poison, LockResult, TryLockError, TryLockResult};
 use crate::sys_common::rwlock as sys;
 
 /// A reader-writer lock