| // 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 alloc_crate::boxed::Box; |
| use core::fmt; |
| use core::ops::Deref; |
| use crate::sys_common::poison::{self, LockResult, TryLockError, TryLockResult}; |
| use crate::sys_common::remutex as sys; |
| |
| pub use crate::sys_common::remutex::SgxReentrantThreadMutex; |
| |
| |
| /// A re-entrant mutual exclusion |
| /// |
| /// This mutex will block *other* threads waiting for the lock to become |
| /// available. The thread which has already locked the mutex can lock it |
| /// multiple times without blocking, preventing a common source of deadlocks. |
| pub struct SgxReentrantMutex<T> { |
| inner: Box<sys::SgxReentrantThreadMutex>, |
| poison: poison::Flag, |
| data: T, |
| } |
| |
| unsafe impl<T: Send> Send for SgxReentrantMutex<T> {} |
| unsafe impl<T: Send> Sync for SgxReentrantMutex<T> {} |
| |
| impl<T> SgxReentrantMutex<T> { |
| /// Creates a new reentrant mutex in an unlocked state. |
| pub fn new(t: T) -> SgxReentrantMutex<T> { |
| SgxReentrantMutex{ |
| inner: Box::new(sys::SgxReentrantThreadMutex::new()), |
| poison: poison::Flag::new(), |
| data: t, |
| } |
| } |
| |
| /// Acquires a mutex, blocking the current thread until it is able to do so. |
| /// |
| /// This function will block the caller until it is available to acquire the mutex. |
| /// Upon returning, the thread is the only thread with the mutex held. When the thread |
| /// calling this method already holds the lock, the call shall succeed without |
| /// blocking. |
| /// |
| /// # Errors |
| /// |
| /// 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<SgxReentrantMutexGuard<'_, T>> { |
| unsafe { |
| self.inner.lock(); |
| SgxReentrantMutexGuard::new(self) |
| } |
| } |
| |
| /// Attempts to acquire this lock. |
| /// |
| /// If the lock could not be acquired at this time, then `Err` is returned. |
| /// Otherwise, an RAII guard is returned. |
| /// |
| /// This function does not block. |
| /// |
| /// # Errors |
| /// |
| /// 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<SgxReentrantMutexGuard<'_, T>> { |
| unsafe { |
| match self.inner.try_lock() { |
| Ok(_) => Ok(SgxReentrantMutexGuard::new(self)?), |
| Err(_) => Err(TryLockError::WouldBlock), |
| } |
| } |
| } |
| } |
| |
| impl<T> Drop for SgxReentrantMutex<T> { |
| fn drop(&mut self) { |
| // This is actually safe b/c we know that there is no further usage of |
| // this mutex (it's up to the user to arrange for a mutex to get |
| // dropped, that's not our job) |
| let result = unsafe { self.inner.destroy() }; |
| debug_assert_eq!(result, Ok(()), "Error when destroy an SgxReentrantMutex: {}", result.unwrap_err()); |
| } |
| } |
| |
| impl<T: fmt::Debug + 'static> fmt::Debug for SgxReentrantMutex<T> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| match self.try_lock() { |
| Ok(guard) => f.debug_struct("SgxReentrantMutex").field("data", &*guard).finish(), |
| Err(TryLockError::Poisoned(err)) => { |
| f.debug_struct("SgxReentrantMutex").field("data", &**err.get_ref()).finish() |
| }, |
| Err(TryLockError::WouldBlock) => { |
| struct LockedPlaceholder; |
| impl fmt::Debug for LockedPlaceholder { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.write_str("<locked>") |
| } |
| } |
| |
| f.debug_struct("SgxReentrantMutex").field("data", &LockedPlaceholder).finish() |
| } |
| } |
| } |
| } |
| |
| /// An RAII implementation of a "scoped lock" of a mutex. When this structure is |
| /// dropped (falls out of scope), the lock will be unlocked. |
| /// |
| /// The data protected by the mutex can be accessed through this guard via its |
| /// Deref implementation. |
| /// |
| /// # Mutability |
| /// |
| /// Unlike `MutexGuard`, `ReentrantMutexGuard` does not implement `DerefMut`, |
| /// because implementation of the trait would violate Rust’s reference aliasing |
| /// rules. Use interior mutability (usually `RefCell`) in order to mutate the |
| /// guarded data. |
| #[must_use] |
| pub struct SgxReentrantMutexGuard<'a, T: 'a> { |
| // funny underscores due to how Deref currently works (it disregards field |
| // privacy). |
| lock: &'a SgxReentrantMutex<T>, |
| poison: poison::Guard, |
| } |
| |
| impl<T> !Send for SgxReentrantMutexGuard<'_, T> {} |
| |
| impl<'mutex, T> SgxReentrantMutexGuard<'mutex, T> { |
| fn new(lock: &'mutex SgxReentrantMutex<T>) -> LockResult<SgxReentrantMutexGuard<'mutex, T>> { |
| poison::map_result(lock.poison.borrow(), |guard| { |
| SgxReentrantMutexGuard { |
| lock: lock, |
| poison: guard, |
| } |
| }) |
| } |
| } |
| |
| impl<T> Deref for SgxReentrantMutexGuard<'_, T> { |
| type Target = T; |
| |
| fn deref(&self) -> &T { |
| &self.lock.data |
| } |
| } |
| |
| impl<T> Drop for SgxReentrantMutexGuard<'_, T> { |
| #[inline] |
| fn drop(&mut self) { |
| let result = unsafe { |
| self.lock.poison.done(&self.poison); |
| self.lock.inner.unlock() |
| }; |
| debug_assert_eq!(result, Ok(()), "Error when unlocking an SgxReentrantMutex: {}", result.unwrap_err()); |
| } |
| } |
| |
| impl<T: fmt::Debug> fmt::Debug for SgxReentrantMutexGuard<'_, T> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| fmt::Debug::fmt(&**self, f) |
| } |
| } |
| |
| impl<T: fmt::Display> fmt::Display for SgxReentrantMutexGuard<'_, T> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| (**self).fmt(f) |
| } |
| } |