f allow recursive read locks fully

Author: TheBlueMatt

lightning/src/debug_sync.rs

@@ -74,7 +74,9 @@ impl MutexMetadata {
 		}
 	}
 
-	fn pre_lock(this: &Arc<MutexMetadata>, read: bool) {
+	// 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
@@ -101,9 +103,14 @@ impl MutexMetadata {
 				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
@@ -167,7 +174,7 @@ impl<T> Mutex<T> {
 	}
 
 	pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
-		MutexMetadata::pre_lock(&self.deps, false);
+		MutexMetadata::pre_lock(&self.deps);
 		self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
 	}
 
@@ -187,6 +194,7 @@ pub struct RwLock<T: Sized> {
 
 pub struct RwLockReadGuard<'a, T: Sized + 'a> {
 	mutex: &'a RwLock<T>,
+	first_lock :bool,
 	lock: StdRwLockReadGuard<'a, T>,
 }
 
@@ -205,6 +213,7 @@ impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
 
 impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
 	fn drop(&mut self) {
+		if !self.first_lock { return; }
 		MUTEXES_HELD.with(|held| {
 			held.borrow_mut().remove(&self.mutex.deps);
 		});
@@ -239,12 +248,12 @@ impl<T> RwLock<T> {
 	}
 
 	pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
-		MutexMetadata::pre_lock(&self.deps, true);
-		self.inner.read().map(|lock| RwLockReadGuard { mutex: self, 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>> {
-		MutexMetadata::pre_lock(&self.deps, false);
+		MutexMetadata::pre_lock(&self.deps);
 		self.inner.write().map(|lock| RwLockWriteGuard { mutex: self, lock }).map_err(|_| ())
 	}