From 4c70d999d6ecbf634dfb84de2d1a3195ad63f9bb Mon Sep 17 00:00:00 2001
From: Bert Peters <bert@bertptrs.nl>
Date: Sat, 10 Jul 2021 12:07:40 +0200
Subject: [PATCH] Create type aliases for parking_lot::RwLock

---
 src/parkinglot.rs | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/src/parkinglot.rs b/src/parkinglot.rs
index 2524aa3..7158623 100644
--- a/src/parkinglot.rs
+++ b/src/parkinglot.rs
@@ -21,6 +21,7 @@ debug_variant!(
     parking_lot::RawFairMutex
 );
 debug_variant!(DebugRawMutex, TracingRawMutex, parking_lot::RawMutex);
+debug_variant!(DebugRawRwLock, TracingRawRwLock, parking_lot::RawRwLock);
 
 /// Dependency tracking fair mutex. See: [`parking_lot::FairMutex`].
 pub type TracingFairMutex<T> = lock_api::Mutex<TracingRawFairMutex, T>;
@@ -47,6 +48,10 @@ pub type DebugMutex<T> = lock_api::Mutex<DebugRawMutex, T>;
 pub type DebugMutexGuard<'a, T> = lock_api::MutexGuard<'a, DebugRawMutex, T>;
 
 /// Dependency tracking reentrant mutex. See: [`parking_lot::ReentrantMutex`].
+///
+/// **Note:** due to the way dependencies are tracked, this mutex can only be acquired directly
+/// after itself. Acquiring any other mutex in between introduces a dependency cycle, and will
+/// therefore be rejected.
 pub type TracingReentrantMutex<T> =
     lock_api::ReentrantMutex<TracingWrapper<parking_lot::RawMutex>, parking_lot::RawThreadId, T>;
 /// Mutex guard for [`TracingReentrantMutex`].
@@ -67,6 +72,23 @@ pub type DebugReentrantMutex<T> =
 pub type DebugReentrantMutexGuard<'a, T> =
     lock_api::ReentrantMutexGuard<'a, DebugRawMutex, parking_lot::RawThreadId, T>;
 
+/// Dependency tracking RwLock. See: [`parking_lot::RwLock`].
+pub type TracingRwLock<T> = lock_api::RwLock<TracingRawRwLock, T>;
+/// Read guard for [`TracingRwLock`].
+pub type TracingRwLockReadGuard<'a, T> = lock_api::RwLockReadGuard<'a, TracingRawRwLock, T>;
+/// Write guard for [`TracingRwLock`].
+pub type TracingRwLockWriteGuard<'a, T> = lock_api::RwLockWriteGuard<'a, TracingRawRwLock, T>;
+
+/// Debug-only dependency tracking RwLock.
+///
+/// If debug assertions are enabled this resolved to [`TracingRwLock`] and to
+/// [`parking_lot::RwLock`] otherwise.
+pub type DebugRwLock<T> = lock_api::RwLock<DebugRawRwLock, T>;
+/// Read guard for [`TracingRwLock`].
+pub type DebugRwLockReadGuard<'a, T> = lock_api::RwLockReadGuard<'a, DebugRawRwLock, T>;
+/// Write guard for [`TracingRwLock`].
+pub type DebugRwLockWriteGuard<'a, T> = lock_api::RwLockWriteGuard<'a, DebugRawRwLock, T>;
+
 /// A dependency-tracking wrapper for [`parking_lot::Once`].
 #[derive(Debug, Default)]
 pub struct TracingOnce {
@@ -154,6 +176,21 @@ mod tests {
         }
     }
 
+    #[test]
+    fn test_rwlock_usage() {
+        let lock = Arc::new(TracingRwLock::new(()));
+        let lock2 = Arc::clone(&lock);
+
+        let _read_lock = lock.read();
+
+        // Should be able to acquire lock in the background
+        thread::spawn(move || {
+            let _read_lock = lock2.read();
+        })
+        .join()
+        .unwrap();
+    }
+
     #[test]
     fn test_once_usage() {
         let once = Arc::new(TracingOnce::new());