}
}
- fn pre_lock(this: &Arc<MutexMetadata>) {
+ // Returns whether we were a recursive lock (only relevant for read)
+ fn _pre_lock(this: &Arc<MutexMetadata>, read: bool) -> bool {
+ let mut inserted = false;
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() {
+ 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 mutex while it was held!");
+ }
for locked_dep in locked.locked_before.lock().unwrap().iter() {
if *locked_dep == *this {
#[cfg(feature = "backtrace")]
this.locked_before.lock().unwrap().insert(Arc::clone(locked));
}
held.borrow_mut().insert(Arc::clone(this));
+ inserted = true;
});
+ inserted
}
+ fn pre_lock(this: &Arc<MutexMetadata>) { Self::_pre_lock(this, false); }
+ fn pre_read_lock(this: &Arc<MutexMetadata>) -> bool { Self::_pre_lock(this, true) }
+
fn try_locked(this: &Arc<MutexMetadata>) {
MUTEXES_HELD.with(|held| {
// Since a try-lock will simply fail if the lock is held already, we do not
}
}
-pub struct RwLock<T: ?Sized> {
- inner: StdRwLock<T>
+pub struct RwLock<T: Sized> {
+ inner: StdRwLock<T>,
+ deps: Arc<MutexMetadata>,
}
-pub struct RwLockReadGuard<'a, T: ?Sized + 'a> {
+pub struct RwLockReadGuard<'a, T: Sized + 'a> {
+ mutex: &'a RwLock<T>,
+ first_lock: bool,
lock: StdRwLockReadGuard<'a, T>,
}
-pub struct RwLockWriteGuard<'a, T: ?Sized + 'a> {
+pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
+ mutex: &'a RwLock<T>,
lock: StdRwLockWriteGuard<'a, T>,
}
-impl<T: ?Sized> Deref for RwLockReadGuard<'_, T> {
+impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
type Target = T;
fn deref(&self) -> &T {
}
}
-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;
+ }
+ MUTEXES_HELD.with(|held| {
+ held.borrow_mut().remove(&self.mutex.deps);
+ });
+ }
+}
+
+impl<T: Sized> Deref for RwLockWriteGuard<'_, T> {
type Target = T;
fn deref(&self) -> &T {
}
}
-impl<T: ?Sized> DerefMut for RwLockWriteGuard<'_, T> {
+impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
+ fn drop(&mut self) {
+ MUTEXES_HELD.with(|held| {
+ held.borrow_mut().remove(&self.mutex.deps);
+ });
+ }
+}
+
+impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
fn deref_mut(&mut self) -> &mut T {
self.lock.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(MutexMetadata::new()) }
}
pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
- self.inner.read().map(|lock| RwLockReadGuard { lock }).map_err(|_| ())
+ let first_lock = MutexMetadata::pre_read_lock(&self.deps);
+ self.inner.read().map(|lock| RwLockReadGuard { mutex: self, lock, first_lock }).map_err(|_| ())
}
pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
- self.inner.write().map(|lock| RwLockWriteGuard { lock }).map_err(|_| ())
+ MutexMetadata::pre_lock(&self.deps);
+ self.inner.write().map(|lock| RwLockWriteGuard { mutex: self, lock }).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(|lock| RwLockWriteGuard { mutex: self, lock }).map_err(|_| ());
+ if res.is_ok() {
+ MutexMetadata::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 / commitdiff