| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you under the Apache License, Version 2.0 (the |
| // "License"); you may not use this file except in compliance |
| // with the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, |
| // software distributed under the License is distributed on an |
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| // KIND, either express or implied. See the License for the |
| // specific language governing permissions and limitations |
| // under the License.. |
| |
| 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 [`SgxMutex`]es and [`SgxRwLock`]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, SgxMutex as 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); |
| /// } |
| /// }; |
| /// ``` |
| /// [`SgxMutex`]: crate::sync::SgxMutex |
| /// [`SgxRwLock`]: crate::sync::SgxRwLock |
| 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 |
| /// [`SgxMutex`] or the [`try_read`] and [`try_write`] methods on an [`SgxRwLock`]. |
| /// |
| /// [`try_lock`]: crate::sync::SgxMutex::try_lock |
| /// [`try_read`]: crate::sync::SgxRwLock::try_read |
| /// [`try_write`]: crate::sync::SgxRwLock::try_write |
| /// [`SgxMutex`]: crate::sync::SgxMutex |
| /// [`SgxRwLock`]: crate::sync::SgxRwLock |
| pub enum TryLockError<T> { |
| /// The lock could not be acquired because another thread failed while holding |
| /// the lock. |
| Poisoned(PoisonError<T>), |
| /// The lock could not be acquired at this time because the operation would |
| /// otherwise block. |
| 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 |
| 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 might not |
| /// have been acquired for other reasons. |
| pub type TryLockResult<Guard> = Result<Guard, TryLockError<Guard>>; |
| |
| impl<T> fmt::Debug for PoisonError<T> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_struct("PoisonError").finish_non_exhaustive() |
| } |
| } |
| |
| impl<T> fmt::Display for PoisonError<T> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| "poisoned lock: another task failed inside".fmt(f) |
| } |
| } |
| |
| 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). |
| 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, SgxMutex as 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()); |
| /// ``` |
| 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. |
| 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. |
| pub fn get_mut(&mut self) -> &mut T { |
| &mut self.guard |
| } |
| } |
| |
| impl<T> From<PoisonError<T>> for TryLockError<T> { |
| fn from(err: PoisonError<T>) -> TryLockError<T> { |
| TryLockError::Poisoned(err) |
| } |
| } |
| |
| 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), |
| } |
| } |
| } |
| |
| 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) |
| } |
| } |
| |
| 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))), |
| } |
| } |