Implement tracing mutex for RwLock

src/stdsync.rs

@@ -1,11 +1,30 @@
-//! Tracing Mutex implementations for `std::sync`.
+//! Tracing mutex wrappers for types found in `std::sync`.
+//!
+//! This module provides wrappers for `std::sync` primitives with exactly the same API and
+//! functionality as their counterparts, with the exception that their acquisition order is
+//! tracked.
+//!
+//! ```rust
+//! # use tracing_mutex::stdsync::TracingMutex;
+//! # use tracing_mutex::stdsync::TracingRwLock;
+//! let mutex = TracingMutex::new(());
+//! mutex.lock().unwrap();
+//!
+//! let rwlock = TracingRwLock::new(());
+//! rwlock.read().unwrap();
+//! ```
 use std::fmt;
+use std::mem;
 use std::ops::Deref;
 use std::ops::DerefMut;
+use std::ptr;
 use std::sync::LockResult;
 use std::sync::Mutex;
 use std::sync::MutexGuard;
 use std::sync::PoisonError;
+use std::sync::RwLock;
+use std::sync::RwLockReadGuard;
+use std::sync::RwLockWriteGuard;
 use std::sync::TryLockError;
 use std::sync::TryLockResult;
 
@@ -15,14 +34,14 @@ use crate::next_mutex_id;
 use crate::register_dependency;
 use crate::register_lock;
 
-/// Wrapper for std::sync::Mutex
+/// Wrapper for `std::sync::Mutex`
 #[derive(Debug)]
 pub struct TracingMutex<T> {
     inner: Mutex<T>,
     id: usize,
 }
 
-/// Wrapper for std::sync::MutexGuard
+/// Wrapper for `std::sync::MutexGuard`
 #[derive(Debug)]
 pub struct TracingMutexGuard<'a, T> {
     inner: MutexGuard<'a, T>,
@@ -99,6 +118,20 @@ impl<T> TracingMutex<T> {
     pub fn get_mut(&mut self) -> LockResult<&mut T> {
         self.inner.get_mut()
     }
+
+    pub fn into_inner(self) -> LockResult<T> {
+        self.deregister();
+
+        // Safety: we forget the original immediately after
+        let inner = unsafe { ptr::read(&self.inner) };
+        mem::forget(self);
+
+        inner.into_inner()
+    }
+
+    fn deregister(&self) {
+        get_depedency_graph().remove_node(self.id);
+    }
 }
 
 impl<T: ?Sized + Default> Default for TracingMutex<T> {
@@ -115,9 +148,7 @@ impl<T> From<T> for TracingMutex<T> {
 
 impl<T> Drop for TracingMutex<T> {
     fn drop(&mut self) {
-        let id = self.id;
-
-        get_depedency_graph().remove_node(id);
+        self.deregister();
     }
 }
 
@@ -147,6 +178,150 @@ impl<'a, T> Drop for TracingMutexGuard<'a, T> {
     }
 }
 
+/// Wrapper for `std::sync::RwLock`
+#[derive(Debug)]
+pub struct TracingRwLock<T> {
+    inner: RwLock<T>,
+    id: usize,
+}
+
+/// Hybrid wrapper for both `std::sync::RwLockReadGuard` and `std::sync::RwLockWriteGuard`.
+///
+/// Please refer to [`TracingReadGuard`] and [`TracingWriteGuard`] for usable types.
+#[derive(Debug)]
+pub struct TracingRwLockGuard<'a, T, L> {
+    inner: L,
+    mutex: &'a TracingRwLock<T>,
+}
+
+/// Wrapper around `std::sync::RwLockReadGuard`.
+pub type TracingReadGuard<'a, T> = TracingRwLockGuard<'a, T, RwLockReadGuard<'a, T>>;
+/// Wrapper around `std::sync::RwLockWriteGuard`.
+pub type TracingWriteGuard<'a, T> = TracingRwLockGuard<'a, T, RwLockWriteGuard<'a, T>>;
+
+impl<T> TracingRwLock<T> {
+    pub fn new(t: T) -> Self {
+        Self {
+            inner: RwLock::new(t),
+            id: next_mutex_id(),
+        }
+    }
+
+    pub fn get_id(&self) -> usize {
+        self.id
+    }
+
+    #[track_caller]
+    pub fn read(&self) -> LockResult<TracingReadGuard<T>> {
+        register_dependency(self.id);
+        let result = self.inner.read();
+        register_lock(self.id);
+
+        map_lockresult(result, |lock| TracingRwLockGuard {
+            inner: lock,
+            mutex: self,
+        })
+    }
+
+    #[track_caller]
+    pub fn write(&self) -> LockResult<TracingWriteGuard<T>> {
+        register_dependency(self.id);
+        let result = self.inner.write();
+        register_lock(self.id);
+        let id = self.id;
+
+        get_depedency_graph().remove_node(id);
+        map_lockresult(result, |lock| TracingRwLockGuard {
+            inner: lock,
+            mutex: self,
+        })
+    }
+
+    #[track_caller]
+    pub fn try_read(&self) -> TryLockResult<TracingReadGuard<T>> {
+        register_dependency(self.id);
+        let result = self.inner.try_read();
+        register_lock(self.id);
+
+        map_trylockresult(result, |lock| TracingRwLockGuard {
+            inner: lock,
+            mutex: self,
+        })
+    }
+
+    #[track_caller]
+    pub fn try_write(&self) -> TryLockResult<TracingWriteGuard<T>> {
+        register_dependency(self.id);
+        let result = self.inner.try_write();
+        register_lock(self.id);
+
+        map_trylockresult(result, |lock| TracingRwLockGuard {
+            inner: lock,
+            mutex: self,
+        })
+    }
+
+    pub fn get_mut(&mut self) -> LockResult<&mut T> {
+        self.inner.get_mut()
+    }
+
+    pub fn into_inner(self) -> LockResult<T> {
+        self.deregister();
+
+        // Grab our contents and then forget ourselves
+        // Safety: we immediately forget the mutex after copying
+        let inner = unsafe { ptr::read(&self.inner) };
+        mem::forget(self);
+
+        inner.into_inner()
+    }
+
+    fn deregister(&self) {
+        get_depedency_graph().remove_node(self.id);
+    }
+}
+
+impl<T> Drop for TracingRwLock<T> {
+    fn drop(&mut self) {
+        self.deregister();
+    }
+}
+
+impl<T> Default for TracingRwLock<T>
+where
+    T: Default,
+{
+    fn default() -> Self {
+        Self::new(T::default())
+    }
+}
+
+impl<'a, T, L> Drop for TracingRwLockGuard<'a, T, L> {
+    fn drop(&mut self) {
+        drop_lock(self.mutex.id)
+    }
+}
+
+impl<'a, T, L> Deref for TracingRwLockGuard<'a, T, L>
+where
+    L: Deref<Target = T>,
+{
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        self.inner.deref()
+    }
+}
+
+impl<'a, T, L> DerefMut for TracingRwLockGuard<'a, T, L>
+where
+    L: Deref<Target = T> + DerefMut,
+{
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.inner.deref_mut()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use std::sync::Arc;
@@ -174,6 +349,28 @@ mod tests {
         handle.join().unwrap();
     }
 
+    #[test]
+    fn test_rwlock_usage() {
+        let _graph_lock = GRAPH_MUTEX.lock();
+
+        let rwlock = Arc::new(TracingRwLock::new(()));
+        let rwlock_clone = rwlock.clone();
+
+        let _read_lock = rwlock.read().unwrap();
+
+        // Now try to cause a blocking exception in another thread
+        let handle = thread::spawn(move || {
+            let write_result = rwlock_clone.try_write().unwrap_err();
+
+            assert!(matches!(write_result, TryLockError::WouldBlock));
+
+            // Should be able to get a read lock just fine.
+            let _ = rwlock_clone.read().unwrap();
+        });
+
+        handle.join().unwrap();
+    }
+
     #[test]
     #[should_panic(expected = "Mutex order graph should not have cycles")]
     fn test_detect_cycle() {