}
thread_local! {
- /// We track the set of locks currently held by a reference to their `MutexMetadata`
- static MUTEXES_HELD: RefCell<HashSet<Arc<MutexMetadata>>> = RefCell::new(HashSet::new());
+ /// We track the set of locks currently held by a reference to their `LockMetadata`
+ static LOCKS_HELD: RefCell<HashSet<Arc<LockMetadata>>> = RefCell::new(HashSet::new());
}
-static MUTEX_IDX: AtomicUsize = AtomicUsize::new(0);
+static LOCK_IDX: AtomicUsize = AtomicUsize::new(0);
-/// Metadata about a single mutex, by id, the set of things locked-before it, and the backtrace of
+/// Metadata about a single lock, by id, the set of things locked-before it, and the backtrace of
/// when the Mutex itself was constructed.
-struct MutexMetadata {
- mutex_idx: u64,
- locked_before: StdMutex<HashSet<Arc<MutexMetadata>>>,
+struct LockMetadata {
+ lock_idx: u64,
+ locked_before: StdMutex<HashSet<Arc<LockMetadata>>>,
#[cfg(feature = "backtrace")]
- mutex_construction_bt: Backtrace,
+ lock_construction_bt: Backtrace,
}
-impl PartialEq for MutexMetadata {
- fn eq(&self, o: &MutexMetadata) -> bool { self.mutex_idx == o.mutex_idx }
+impl PartialEq for LockMetadata {
+ fn eq(&self, o: &LockMetadata) -> bool { self.lock_idx == o.lock_idx }
}
-impl Eq for MutexMetadata {}
-impl std::hash::Hash for MutexMetadata {
- fn hash<H: std::hash::Hasher>(&self, hasher: &mut H) { hasher.write_u64(self.mutex_idx); }
+impl Eq for LockMetadata {}
+impl std::hash::Hash for LockMetadata {
+ fn hash<H: std::hash::Hasher>(&self, hasher: &mut H) { hasher.write_u64(self.lock_idx); }
+}
+
+impl LockMetadata {
+ fn new() -> LockMetadata {
+ LockMetadata {
+ locked_before: StdMutex::new(HashSet::new()),
+ lock_idx: LOCK_IDX.fetch_add(1, Ordering::Relaxed) as u64,
+ #[cfg(feature = "backtrace")]
+ lock_construction_bt: Backtrace::new(),
+ }
+ }
+
+ // Returns whether we were a recursive lock (only relevant for read)
+ fn _pre_lock(this: &Arc<LockMetadata>, read: bool) -> bool {
+ let mut inserted = false;
+ LOCKS_HELD.with(|held| {
+ // For each lock which is currently locked, check that no lock's locked-before
+ // set includes the lock we're about to lock, which would imply a lockorder
+ // inversion.
+ for locked in held.borrow().iter() {
+ if read && *locked == *this {
+ // Recursive read locks are explicitly allowed
+ return;
+ }
+ }
+ for locked in held.borrow().iter() {
+ if !read && *locked == *this {
+ panic!("Tried to lock a lock while it was held!");
+ }
+ for locked_dep in locked.locked_before.lock().unwrap().iter() {
+ if *locked_dep == *this {
+ #[cfg(feature = "backtrace")]
+ panic!("Tried to violate existing lockorder.\nMutex that should be locked after the current lock was created at the following backtrace.\nNote that to get a backtrace for the lockorder violation, you should set RUST_BACKTRACE=1\n{:?}", locked.lock_construction_bt);
+ #[cfg(not(feature = "backtrace"))]
+ panic!("Tried to violate existing lockorder. Build with the backtrace feature for more info.");
+ }
+ }
+ // Insert any already-held locks in our locked-before set.
+ this.locked_before.lock().unwrap().insert(Arc::clone(locked));
+ }
+ held.borrow_mut().insert(Arc::clone(this));
+ inserted = true;
+ });
+ inserted
+ }
+
+ fn pre_lock(this: &Arc<LockMetadata>) { Self::_pre_lock(this, false); }
+ fn pre_read_lock(this: &Arc<LockMetadata>) -> bool { Self::_pre_lock(this, true) }
+
+ fn try_locked(this: &Arc<LockMetadata>) {
+ LOCKS_HELD.with(|held| {
+ // Since a try-lock will simply fail if the lock is held already, we do not
+ // consider try-locks to ever generate lockorder inversions. However, if a try-lock
+ // succeeds, we do consider it to have created lockorder dependencies.
+ for locked in held.borrow().iter() {
+ this.locked_before.lock().unwrap().insert(Arc::clone(locked));
+ }
+ held.borrow_mut().insert(Arc::clone(this));
+ });
+ }
}
pub struct Mutex<T: Sized> {
inner: StdMutex<T>,
- deps: Arc<MutexMetadata>,
+ deps: Arc<LockMetadata>,
}
#[must_use = "if unused the Mutex will immediately unlock"]
impl<T: Sized> Drop for MutexGuard<'_, T> {
fn drop(&mut self) {
- MUTEXES_HELD.with(|held| {
+ LOCKS_HELD.with(|held| {
held.borrow_mut().remove(&self.mutex.deps);
});
}
impl<T> Mutex<T> {
pub fn new(inner: T) -> Mutex<T> {
- Mutex {
- inner: StdMutex::new(inner),
- deps: Arc::new(MutexMetadata {
- locked_before: StdMutex::new(HashSet::new()),
- mutex_idx: MUTEX_IDX.fetch_add(1, Ordering::Relaxed) as u64,
- #[cfg(feature = "backtrace")]
- mutex_construction_bt: Backtrace::new(),
- }),
- }
+ Mutex { inner: StdMutex::new(inner), deps: Arc::new(LockMetadata::new()) }
}
pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
- MUTEXES_HELD.with(|held| {
- // For each mutex which is currently locked, check that no mutex's locked-before
- // set includes the mutex we're about to lock, which would imply a lockorder
- // inversion.
- for locked in held.borrow().iter() {
- for locked_dep in locked.locked_before.lock().unwrap().iter() {
- if *locked_dep == self.deps {
- #[cfg(feature = "backtrace")]
- panic!("Tried to violate existing lockorder.\nMutex that should be locked after the current lock was created at the following backtrace.\nNote that to get a backtrace for the lockorder violation, you should set RUST_BACKTRACE=1\n{:?}", locked.mutex_construction_bt);
- #[cfg(not(feature = "backtrace"))]
- panic!("Tried to violate existing lockorder. Build with the backtrace feature for more info.");
- }
- }
- // Insert any already-held mutexes in our locked-before set.
- self.deps.locked_before.lock().unwrap().insert(Arc::clone(locked));
- }
- held.borrow_mut().insert(Arc::clone(&self.deps));
- });
+ LockMetadata::pre_lock(&self.deps);
self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
}
pub fn try_lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
let res = self.inner.try_lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ());
if res.is_ok() {
- MUTEXES_HELD.with(|held| {
- // Since a try-lock will simply fail if the lock is held already, we do not
- // consider try-locks to ever generate lockorder inversions. However, if a try-lock
- // succeeds, we do consider it to have created lockorder dependencies.
- for locked in held.borrow().iter() {
- self.deps.locked_before.lock().unwrap().insert(Arc::clone(locked));
- }
- held.borrow_mut().insert(Arc::clone(&self.deps));
- });
+ LockMetadata::try_locked(&self.deps);
}
res
}
}
-pub struct RwLock<T: ?Sized> {
- inner: StdRwLock<T>
+pub struct RwLock<T: Sized> {
+ inner: StdRwLock<T>,
+ deps: Arc<LockMetadata>,
}
-pub struct RwLockReadGuard<'a, T: ?Sized + 'a> {
- lock: StdRwLockReadGuard<'a, T>,
+pub struct RwLockReadGuard<'a, T: Sized + 'a> {
+ lock: &'a RwLock<T>,
+ first_lock: bool,
+ guard: StdRwLockReadGuard<'a, T>,
}
-pub struct RwLockWriteGuard<'a, T: ?Sized + 'a> {
- lock: StdRwLockWriteGuard<'a, T>,
+pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
+ lock: &'a RwLock<T>,
+ guard: StdRwLockWriteGuard<'a, T>,
}
-impl<T: ?Sized> Deref for RwLockReadGuard<'_, T> {
+impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
type Target = T;
fn deref(&self) -> &T {
- &self.lock.deref()
+ &self.guard.deref()
}
}
-impl<T: ?Sized> Deref for RwLockWriteGuard<'_, T> {
+impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
+ fn drop(&mut self) {
+ if !self.first_lock {
+ // Note that its not strictly true that the first taken read lock will get unlocked
+ // last, but in practice our locks are always taken as RAII, so it should basically
+ // always be true.
+ return;
+ }
+ LOCKS_HELD.with(|held| {
+ held.borrow_mut().remove(&self.lock.deps);
+ });
+ }
+}
+
+impl<T: Sized> Deref for RwLockWriteGuard<'_, T> {
type Target = T;
fn deref(&self) -> &T {
- &self.lock.deref()
+ &self.guard.deref()
+ }
+}
+
+impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
+ fn drop(&mut self) {
+ LOCKS_HELD.with(|held| {
+ held.borrow_mut().remove(&self.lock.deps);
+ });
}
}
-impl<T: ?Sized> DerefMut for RwLockWriteGuard<'_, T> {
+impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
fn deref_mut(&mut self) -> &mut T {
- self.lock.deref_mut()
+ self.guard.deref_mut()
}
}
impl<T> RwLock<T> {
pub fn new(inner: T) -> RwLock<T> {
- RwLock { inner: StdRwLock::new(inner) }
+ RwLock { inner: StdRwLock::new(inner), deps: Arc::new(LockMetadata::new()) }
}
pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
- self.inner.read().map(|lock| RwLockReadGuard { lock }).map_err(|_| ())
+ let first_lock = LockMetadata::pre_read_lock(&self.deps);
+ self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard, first_lock }).map_err(|_| ())
}
pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
- self.inner.write().map(|lock| RwLockWriteGuard { lock }).map_err(|_| ())
+ LockMetadata::pre_lock(&self.deps);
+ self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ())
}
pub fn try_write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
- self.inner.try_write().map(|lock| RwLockWriteGuard { lock }).map_err(|_| ())
+ let res = self.inner.try_write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ());
+ if res.is_ok() {
+ LockMetadata::try_locked(&self.deps);
+ }
+ res
+ }
+}
+
+#[test]
+#[should_panic]
+fn recursive_lock_fail() {
+ let mutex = Mutex::new(());
+ let _a = mutex.lock().unwrap();
+ let _b = mutex.lock().unwrap();
+}
+
+#[test]
+fn recursive_read() {
+ let lock = RwLock::new(());
+ let _a = lock.read().unwrap();
+ let _b = lock.read().unwrap();
+}
+
+#[test]
+#[should_panic]
+fn lockorder_fail() {
+ let a = Mutex::new(());
+ let b = Mutex::new(());
+ {
+ let _a = a.lock().unwrap();
+ let _b = b.lock().unwrap();
+ }
+ {
+ let _b = b.lock().unwrap();
+ let _a = a.lock().unwrap();
+ }
+}
+
+#[test]
+#[should_panic]
+fn write_lockorder_fail() {
+ let a = RwLock::new(());
+ let b = RwLock::new(());
+ {
+ let _a = a.write().unwrap();
+ let _b = b.write().unwrap();
+ }
+ {
+ let _b = b.write().unwrap();
+ let _a = a.write().unwrap();
+ }
+}
+
+#[test]
+#[should_panic]
+fn read_lockorder_fail() {
+ let a = RwLock::new(());
+ let b = RwLock::new(());
+ {
+ let _a = a.read().unwrap();
+ let _b = b.read().unwrap();
+ }
+ {
+ let _b = b.read().unwrap();
+ let _a = a.read().unwrap();
+ }
+}
+
+#[test]
+fn read_recurisve_no_lockorder() {
+ // Like the above, but note that no lockorder is implied when we recursively read-lock a
+ // RwLock, causing this to pass just fine.
+ let a = RwLock::new(());
+ let b = RwLock::new(());
+ let _outer = a.read().unwrap();
+ {
+ let _a = a.read().unwrap();
+ let _b = b.read().unwrap();
+ }
+ {
+ let _b = b.read().unwrap();
+ let _a = a.read().unwrap();
+ }
+}
+
+#[test]
+#[should_panic]
+fn read_write_lockorder_fail() {
+ let a = RwLock::new(());
+ let b = RwLock::new(());
+ {
+ let _a = a.write().unwrap();
+ let _b = b.read().unwrap();
+ }
+ {
+ let _b = b.read().unwrap();
+ let _a = a.write().unwrap();
}
}
projects / rust-lightning / blobdiff