Bump version

21: Prepare for release v0.2.1 r=bertptrs a=bertptrs



Co-authored-by: Bert Peters <bert@bertptrs.nl>

.github/workflows/ci.yml

@@ -2,12 +2,14 @@ on:
   push:
     branches:
       - master
+      - staging
+      - trying
   pull_request:
 
 name: Continuous integration
 
 jobs:
-  ci:
+  tests:
     name: Rust project
     runs-on: ubuntu-latest
     strategy:
@@ -30,10 +32,13 @@ jobs:
       - uses: actions-rs/cargo@v1
         with:
           command: build
+          # --all-targets ensures that we also build the benchmarks and tests already.
+          args: --all-features --all-targets
 
       - uses: actions-rs/cargo@v1
         with:
           command: test
+          args: --all-features
 
       - uses: actions-rs/cargo@v1
         with:
@@ -43,4 +48,23 @@ jobs:
       - uses: actions-rs/cargo@v1
         with:
           command: clippy
-          args: -- -D warnings
+          args: --all-features --all-targets -- -D warnings
+
+  docs:
+    name: Documentation build
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+          override: true
+
+      - name: Build documentation
+        env:
+          # Build the docs like docs.rs builds it
+          RUSTDOCFLAGS: --cfg docsrs
+        run: cargo doc --all-features

CHANGELOG.md

@@ -6,6 +6,44 @@ adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+## [0.2.1] - 2022-05-23
+
+### Added
+
+- Build [docs.rs] documentation with all features enabled for completeness.
+- Add support for `std::sync::Condvar`
+
+### Fixed
+
+- The `parkinglot` module is now correctly enabled by the `parkinglot` feature rather than the
+  `lockapi` feature.
+
+## [0.2.0] - 2022-05-07
+
+### Added
+- Generic support for wrapping mutexes that implement the traits provided by the
+  [`lock_api`][lock_api] crate. This can be used for creating support for other mutex providers that
+  implement it.
+
+- Support for [`parking_lot`][parking_lot] mutexes. Support includes type aliases for all
+  provided mutex types as well as a dedicated `Once` wrapper.
+
+- Simple benchmark to track the rough performance penalty incurred by dependency tracking.
+
+### Breaking
+
+- The library now requires edition 2021.
+
+- The `Mutex`- and `RwLockGuards` now dereference to `T` rather than the lock guard they wrap. This
+  is technically a bugfix but can theoretically break existing code.
+
+- Self-cycles are no longer allowed for lock dependencies. They previously were because it usually
+  isn't a problem, but it can create RWR deadlocks with `RwLocks`.
+
+### Changed
+
+- The project now targets edition 2021
+
 ## [0.1.2] - 2021-05-27
 
 ### Added
@@ -29,7 +67,13 @@ adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 Initial release.
 
-[Unreleased]: https://github.com/bertptrs/tracing-mutex/compare/v0.1.2...HEAD
-[0.1.2]: https://github.com/bertptrs/tracing-mutex/compare/v0.1.2...v0.1.2
+[Unreleased]: https://github.com/bertptrs/tracing-mutex/compare/v0.2.1...HEAD
+[0.2.1]: https://github.com/bertptrs/tracing-mutex/compare/v0.2.0...v0.2.1
+[0.2.0]: https://github.com/bertptrs/tracing-mutex/compare/v0.1.2...v0.2.0
+[0.1.2]: https://github.com/bertptrs/tracing-mutex/compare/v0.1.1...v0.1.2
 [0.1.1]: https://github.com/bertptrs/tracing-mutex/compare/v0.1.0...v0.1.1
 [0.1.0]: https://github.com/bertptrs/tracing-mutex/releases/tag/v0.1.0
+
+[docs.rs]: https://docs.rs/tracing-mutex/latest/tracing_mutex/
+[lock_api]: https://docs.rs/lock_api/
+[parking_lot]: https://docs.rs/parking_lot/

Cargo.toml

@@ -1,8 +1,8 @@
 [package]
 name = "tracing-mutex"
-version = "0.1.2"
+version = "0.2.1"
 authors = ["Bert Peters <bert@bertptrs.nl>"]
-edition = "2018"
+edition = "2021"
 license = "MIT OR Apache-2.0"
 documentation = "https://docs.rs/tracing-mutex"
 categories = ["concurrency", "development-tools::debugging"]
@@ -11,8 +11,26 @@ description = "Ensure deadlock-free mutexes by allocating in order, or else."
 readme = "README.md"
 repository = "https://github.com/bertptrs/tracing-mutex"
 
+[package.metadata.docs.rs]
+# Build docs for all features so the documentation is more complete
+all-features = true
+# Set custom cfg so we can enable docs.rs magic
+rustdoc-args = ["--cfg", "docsrs"]
+
 [dependencies]
 lazy_static = "1"
+lock_api = { version = "0.4", optional = true }
+parking_lot = { version = "0.11", optional = true }
 
 [dev-dependencies]
+criterion = "0.3"
 rand = "0.8"
+
+[[bench]]
+name = "mutex"
+harness = false
+
+[features]
+# Feature names do not match crate names pending namespaced features.
+lockapi = ["lock_api"]
+parkinglot = ["parking_lot", "lockapi"]

LICENSE-APACHE

@@ -186,7 +186,7 @@ APPENDIX: How to apply the Apache License to your work.
    same "printed page" as the copyright notice for easier
    identification within third-party archives.
 
-Copyright [yyyy] [name of copyright owner]
+Copyright 2022 Bert Peters
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.

LICENSE-MIT

@@ -1,4 +1,4 @@
-Copyright © 2021 Bert Peters
+Copyright © 2022 Bert Peters
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
 associated documentation files (the “Software”), to deal in the Software without restriction,

README.md

@@ -34,7 +34,7 @@ Add this dependency to your `Cargo.lock` file like any other:
 
 ```toml
 [dependencies]
-tracing-mutex = "0.1"
+tracing-mutex = "0.2"
 ```
 
 Then use the locks provided by this library instead of the ones you would use otherwise.
@@ -59,12 +59,23 @@ performance penalty in your production environment, this library also offers deb
 when debug assertions are enabled, and to `Mutex` when they are not. Similar helper types are
 available for other synchronization primitives.
 
+### Features
+
+- Dependency-tracking wrappers for all locking primitives
+- Optional opt-out for release mode code
+- Support for primitives from:
+  - `std::sync`
+  - `parking_lot`
+  - Any library that implements the `lock_api` traits
+
 ## Future improvements
 
 - Improve performance in lock tracing
 - Optional logging to make debugging easier
 - Better and configurable error handling when detecting cyclic dependencies
-- Support for other locking libraries, such as `parking_lot`
+- Support for other locking libraries
+- Support for async locking libraries
+- Support for `Send` mutex guards
 
 **Note:** `parking_lot` has already began work on its own deadlock detection mechanism, which works
 in a different way. Both can be complimentary.

benches/mutex.rs

@@ -0,0 +1,82 @@
+use std::sync::Arc;
+use std::sync::Mutex;
+
+use criterion::criterion_group;
+use criterion::criterion_main;
+use criterion::BenchmarkId;
+use criterion::Criterion;
+use criterion::Throughput;
+use rand::prelude::*;
+use tracing_mutex::stdsync::TracingMutex;
+
+const SAMPLE_SIZES: [usize; 5] = [10, 30, 100, 300, 1000];
+
+/// Reproducibly generate random combinations a, b where the index(a) < index(b)
+///
+/// All combinations are generated
+fn generate_combinations<T>(options: &[Arc<T>]) -> Vec<(Arc<T>, Arc<T>)> {
+    let mut combinations = Vec::new();
+
+    for (i, first) in options.iter().enumerate() {
+        for second in options.iter().skip(i + 1) {
+            combinations.push((Arc::clone(first), Arc::clone(second)));
+        }
+    }
+
+    let mut rng = StdRng::seed_from_u64(42);
+
+    combinations.shuffle(&mut rng);
+
+    combinations
+}
+
+/// Take two arbitrary mutexes, lock the first, lock the second while holding the first.
+fn benchmark_baseline(c: &mut Criterion) {
+    let mut group = c.benchmark_group("baseline");
+
+    for nodes in SAMPLE_SIZES {
+        group.throughput(Throughput::Elements((nodes * (nodes - 1) / 2) as u64));
+        group.bench_with_input(BenchmarkId::from_parameter(nodes), &nodes, |b, &s| {
+            b.iter_batched(
+                || {
+                    let mutexes: Vec<_> = (0..s).map(|_| Arc::new(Mutex::new(()))).collect();
+                    generate_combinations(&mutexes)
+                },
+                |combinations| {
+                    for (first, second) in combinations {
+                        let _first = first.lock();
+                        let _second = second.lock();
+                    }
+                },
+                criterion::BatchSize::SmallInput,
+            )
+        });
+    }
+}
+
+/// Same as [`benchmark_baseline`] but now while tracking dependencies.
+fn benchmark_tracing_mutex(c: &mut Criterion) {
+    let mut group = c.benchmark_group("tracing_mutex");
+
+    for nodes in SAMPLE_SIZES {
+        group.throughput(Throughput::Elements((nodes * (nodes - 1) / 2) as u64));
+        group.bench_with_input(BenchmarkId::from_parameter(nodes), &nodes, |b, &s| {
+            b.iter_batched(
+                || {
+                    let mutexes: Vec<_> = (0..s).map(|_| Arc::new(TracingMutex::new(()))).collect();
+                    generate_combinations(&mutexes)
+                },
+                |combinations| {
+                    for (first, second) in combinations {
+                        let _first = first.lock();
+                        let _second = second.lock();
+                    }
+                },
+                criterion::BatchSize::SmallInput,
+            )
+        });
+    }
+}
+
+criterion_group!(benches, benchmark_baseline, benchmark_tracing_mutex);
+criterion_main!(benches);

bors.toml

@@ -0,0 +1,5 @@
+status = [
+    'Rust project (stable)',
+    'Rust project (beta)',
+    'Documentation build',
+]

src/graph.rs

@@ -1,4 +1,3 @@
-use std::array::IntoIter;
 use std::cell::Cell;
 use std::collections::HashMap;
 use std::collections::HashSet;
@@ -99,8 +98,8 @@ where
     /// would introduce a cycle, the edge is rejected and `false` is returned.
     pub(crate) fn add_edge(&mut self, x: V, y: V) -> bool {
         if x == y {
-            // self-edges are not considered cycles
-            return true;
+            // self-edges are always considered cycles
+            return false;
         }
 
         let (_, out_edges, ub) = self.add_node(x);
@@ -116,7 +115,7 @@ where
 
         if lb < ub {
             // This edge might introduce a cycle, need to recompute the topological sort
-            let mut visited = IntoIter::new([x, y]).collect();
+            let mut visited = [x, y].into_iter().collect();
             let mut delta_f = Vec::new();
             let mut delta_b = Vec::new();
 
@@ -227,6 +226,14 @@ mod tests {
 
     use super::*;
 
+    #[test]
+    fn test_no_self_cycle() {
+        // Regression test for https://github.com/bertptrs/tracing-mutex/issues/7
+        let mut graph = DiGraph::default();
+
+        assert!(!graph.add_edge(1, 1));
+    }
+
     #[test]
     fn test_digraph() {
         let mut graph = DiGraph::default();
@@ -259,7 +266,9 @@ mod tests {
 
         for i in 0..NUM_NODES {
             for j in i..NUM_NODES {
-                edges.push((i, j));
+                if i != j {
+                    edges.push((i, j));
+                }
             }
         }
 

src/lib.rs

@@ -45,6 +45,7 @@
 //! enabled, and to the underlying mutex when they're not.
 //!
 //! [paper]: https://whileydave.com/publications/pk07_jea/
+#![cfg_attr(docsrs, feature(doc_cfg))]
 use std::cell::RefCell;
 use std::cell::UnsafeCell;
 use std::fmt;
@@ -60,10 +61,22 @@ use std::sync::Once;
 use std::sync::PoisonError;
 
 use lazy_static::lazy_static;
+#[cfg(feature = "lockapi")]
+#[cfg_attr(docsrs, doc(cfg(feature = "lockapi")))]
+pub use lock_api;
+#[cfg(feature = "parkinglot")]
+#[cfg_attr(docsrs, doc(cfg(feature = "parkinglot")))]
+pub use parking_lot;
 
 use crate::graph::DiGraph;
 
 mod graph;
+#[cfg(feature = "lockapi")]
+#[cfg_attr(docsrs, doc(cfg(feature = "lockapi")))]
+pub mod lockapi;
+#[cfg(feature = "parkinglot")]
+#[cfg_attr(docsrs, doc(cfg(feature = "parkinglot")))]
+pub mod parkinglot;
 pub mod stdsync;
 
 /// Counter for Mutex IDs. Atomic avoids the need for locking.
@@ -120,6 +133,16 @@ impl MutexId {
     ///
     /// This method panics if the new dependency would introduce a cycle.
     pub fn get_borrowed(&self) -> BorrowedMutex {
+        self.mark_held();
+        BorrowedMutex(self)
+    }
+
+    /// Mark this lock as held for the purposes of dependency tracking.
+    ///
+    /// # Panics
+    ///
+    /// This method panics if the new dependency would introduce a cycle.
+    pub fn mark_held(&self) {
         let creates_cycle = HELD_LOCKS.with(|locks| {
             if let Some(&previous) = locks.borrow().last() {
                 let mut graph = get_dependency_graph();
@@ -136,7 +159,22 @@ impl MutexId {
         }
 
         HELD_LOCKS.with(|locks| locks.borrow_mut().push(self.value()));
-        BorrowedMutex(self)
+    }
+
+    pub unsafe fn mark_released(&self) {
+        HELD_LOCKS.with(|locks| {
+            let mut locks = locks.borrow_mut();
+
+            for (i, &lock) in locks.iter().enumerate().rev() {
+                if lock == self.value() {
+                    locks.remove(i);
+                    return;
+                }
+            }
+
+            // Drop impls shouldn't panic but if this happens something is seriously broken.
+            unreachable!("Tried to drop lock for mutex {:?} but it wasn't held", self)
+        });
     }
 }
 
@@ -187,6 +225,12 @@ impl fmt::Debug for LazyMutexId {
     }
 }
 
+impl Default for LazyMutexId {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 /// Safety: the UnsafeCell is guaranteed to only be accessed mutably from a `Once`.
 unsafe impl Sync for LazyMutexId {}
 
@@ -241,21 +285,8 @@ struct BorrowedMutex<'a>(&'a MutexId);
 /// that is an indication of a serious design flaw in this library.
 impl<'a> Drop for BorrowedMutex<'a> {
     fn drop(&mut self) {
-        let id = self.0;
-
-        HELD_LOCKS.with(|locks| {
-            let mut locks = locks.borrow_mut();
-
-            for (i, &lock) in locks.iter().enumerate().rev() {
-                if lock == id.value() {
-                    locks.remove(i);
-                    return;
-                }
-            }
-
-            // Drop impls shouldn't panic but if this happens something is seriously broken.
-            unreachable!("Tried to drop lock for mutex {:?} but it wasn't held", id)
-        });
+        // Safety: the only way to get a BorrowedMutex is by locking the mutex.
+        unsafe { self.0.mark_released() };
     }
 }
 
@@ -331,7 +362,9 @@ mod tests {
         let mut edges = Vec::with_capacity(NUM_NODES * NUM_NODES);
         for i in 0..NUM_NODES {
             for j in i..NUM_NODES {
-                edges.push((i, j));
+                if i != j {
+                    edges.push((i, j));
+                }
             }
         }
 

src/lockapi.rs

@@ -0,0 +1,348 @@
+//! Wrapper implementations for [`lock_api`].
+//!
+//! This module does not provide any particular mutex implementation by itself, but rather can be
+//! used to add dependency tracking to mutexes that already exist. It implements all of the traits
+//! in `lock_api` based on the one it wraps. Crates such as `spin` and `parking_lot` provide base
+//! primitives that can be wrapped.
+//!
+//! Wrapped mutexes are at least one `usize` larger than the types they wrapped, and must be aligned
+//! to `usize` boundaries. As such, libraries with many mutexes may want to consider the additional
+//! required memory.
+use lock_api::GuardNoSend;
+use lock_api::RawMutex;
+use lock_api::RawMutexFair;
+use lock_api::RawMutexTimed;
+use lock_api::RawRwLock;
+use lock_api::RawRwLockDowngrade;
+use lock_api::RawRwLockFair;
+use lock_api::RawRwLockRecursive;
+use lock_api::RawRwLockRecursiveTimed;
+use lock_api::RawRwLockTimed;
+use lock_api::RawRwLockUpgrade;
+use lock_api::RawRwLockUpgradeDowngrade;
+use lock_api::RawRwLockUpgradeFair;
+use lock_api::RawRwLockUpgradeTimed;
+
+use crate::LazyMutexId;
+
+/// Tracing wrapper for all [`lock_api`] traits.
+///
+/// This wrapper implements any of the locking traits available, given that the wrapped type
+/// implements them. As such, this wrapper can be used both for normal mutexes and rwlocks.
+#[derive(Debug, Default)]
+pub struct TracingWrapper<T> {
+    inner: T,
+    // Need to use a lazy mutex ID to intialize statically.
+    id: LazyMutexId,
+}
+
+impl<T> TracingWrapper<T> {
+    /// Mark this lock as held in the dependency graph.
+    fn mark_held(&self) {
+        self.id.mark_held();
+    }
+
+    /// Mark this lock as released in the dependency graph.
+    ///
+    /// # Safety
+    ///
+    /// This function should only be called when the lock has been previously acquired by this
+    /// thread.
+    unsafe fn mark_released(&self) {
+        self.id.mark_released();
+    }
+
+    /// First mark ourselves as held, then call the locking function.
+    fn lock(&self, f: impl FnOnce()) {
+        self.mark_held();
+        f();
+    }
+
+    /// First call the unlocking function, then mark ourselves as realeased.
+    unsafe fn unlock(&self, f: impl FnOnce()) {
+        f();
+        self.mark_released();
+    }
+
+    /// Conditionally lock the mutex.
+    ///
+    /// First acquires the lock, then runs the provided function. If that function returns true,
+    /// then the lock is kept, otherwise the mutex is immediately marked as relased.
+    ///
+    /// # Returns
+    ///
+    /// The value returned from the callback.
+    fn conditionally_lock(&self, f: impl FnOnce() -> bool) -> bool {
+        // Mark as locked while we try to do the thing
+        self.mark_held();
+
+        if f() {
+            true
+        } else {
+            // Safety: we just locked it above.
+            unsafe { self.mark_released() }
+            false
+        }
+    }
+}
+
+unsafe impl<T> RawMutex for TracingWrapper<T>
+where
+    T: RawMutex,
+{
+    const INIT: Self = Self {
+        inner: T::INIT,
+        id: LazyMutexId::new(),
+    };
+
+    /// Always equal to [`GuardNoSend`], as an implementation detail in the tracking system requires
+    /// this behaviour. May change in the future to reflect the actual guard type from the wrapped
+    /// primitive.
+    type GuardMarker = GuardNoSend;
+
+    fn lock(&self) {
+        self.lock(|| self.inner.lock());
+    }
+
+    fn try_lock(&self) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock())
+    }
+
+    unsafe fn unlock(&self) {
+        self.unlock(|| self.inner.unlock());
+    }
+
+    fn is_locked(&self) -> bool {
+        // Can't use the default implementation as the inner type might've overwritten it.
+        self.inner.is_locked()
+    }
+}
+
+unsafe impl<T> RawMutexFair for TracingWrapper<T>
+where
+    T: RawMutexFair,
+{
+    unsafe fn unlock_fair(&self) {
+        self.unlock(|| self.inner.unlock_fair())
+    }
+
+    unsafe fn bump(&self) {
+        // Bumping effectively doesn't change which locks are held, so we don't need to manage the
+        // lock state.
+        self.inner.bump();
+    }
+}
+
+unsafe impl<T> RawMutexTimed for TracingWrapper<T>
+where
+    T: RawMutexTimed,
+{
+    type Duration = T::Duration;
+
+    type Instant = T::Instant;
+
+    fn try_lock_for(&self, timeout: Self::Duration) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_for(timeout))
+    }
+
+    fn try_lock_until(&self, timeout: Self::Instant) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_until(timeout))
+    }
+}
+
+unsafe impl<T> RawRwLock for TracingWrapper<T>
+where
+    T: RawRwLock,
+{
+    const INIT: Self = Self {
+        inner: T::INIT,
+        id: LazyMutexId::new(),
+    };
+
+    /// Always equal to [`GuardNoSend`], as an implementation detail in the tracking system requires
+    /// this behaviour. May change in the future to reflect the actual guard type from the wrapped
+    /// primitive.
+    type GuardMarker = GuardNoSend;
+
+    fn lock_shared(&self) {
+        self.lock(|| self.inner.lock_shared());
+    }
+
+    fn try_lock_shared(&self) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_shared())
+    }
+
+    unsafe fn unlock_shared(&self) {
+        self.unlock(|| self.inner.unlock_shared());
+    }
+
+    fn lock_exclusive(&self) {
+        self.lock(|| self.inner.lock_exclusive());
+    }
+
+    fn try_lock_exclusive(&self) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_exclusive())
+    }
+
+    unsafe fn unlock_exclusive(&self) {
+        self.unlock(|| self.inner.unlock_exclusive());
+    }
+
+    fn is_locked(&self) -> bool {
+        self.inner.is_locked()
+    }
+}
+
+unsafe impl<T> RawRwLockDowngrade for TracingWrapper<T>
+where
+    T: RawRwLockDowngrade,
+{
+    unsafe fn downgrade(&self) {
+        // Downgrading does not require tracking
+        self.inner.downgrade()
+    }
+}
+
+unsafe impl<T> RawRwLockUpgrade for TracingWrapper<T>
+where
+    T: RawRwLockUpgrade,
+{
+    fn lock_upgradable(&self) {
+        self.lock(|| self.inner.lock_upgradable());
+    }
+
+    fn try_lock_upgradable(&self) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_upgradable())
+    }
+
+    unsafe fn unlock_upgradable(&self) {
+        self.unlock(|| self.inner.unlock_upgradable());
+    }
+
+    unsafe fn upgrade(&self) {
+        self.inner.upgrade();
+    }
+
+    unsafe fn try_upgrade(&self) -> bool {
+        self.inner.try_upgrade()
+    }
+}
+
+unsafe impl<T> RawRwLockFair for TracingWrapper<T>
+where
+    T: RawRwLockFair,
+{
+    unsafe fn unlock_shared_fair(&self) {
+        self.unlock(|| self.inner.unlock_shared_fair());
+    }
+
+    unsafe fn unlock_exclusive_fair(&self) {
+        self.unlock(|| self.inner.unlock_exclusive_fair());
+    }
+
+    unsafe fn bump_shared(&self) {
+        self.inner.bump_shared();
+    }
+
+    unsafe fn bump_exclusive(&self) {
+        self.inner.bump_exclusive();
+    }
+}
+
+unsafe impl<T> RawRwLockRecursive for TracingWrapper<T>
+where
+    T: RawRwLockRecursive,
+{
+    fn lock_shared_recursive(&self) {
+        self.lock(|| self.inner.lock_shared_recursive());
+    }
+
+    fn try_lock_shared_recursive(&self) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_shared_recursive())
+    }
+}
+
+unsafe impl<T> RawRwLockRecursiveTimed for TracingWrapper<T>
+where
+    T: RawRwLockRecursiveTimed,
+{
+    fn try_lock_shared_recursive_for(&self, timeout: Self::Duration) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_shared_recursive_for(timeout))
+    }
+
+    fn try_lock_shared_recursive_until(&self, timeout: Self::Instant) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_shared_recursive_until(timeout))
+    }
+}
+
+unsafe impl<T> RawRwLockTimed for TracingWrapper<T>
+where
+    T: RawRwLockTimed,
+{
+    type Duration = T::Duration;
+
+    type Instant = T::Instant;
+
+    fn try_lock_shared_for(&self, timeout: Self::Duration) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_shared_for(timeout))
+    }
+
+    fn try_lock_shared_until(&self, timeout: Self::Instant) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_shared_until(timeout))
+    }
+
+    fn try_lock_exclusive_for(&self, timeout: Self::Duration) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_exclusive_for(timeout))
+    }
+
+    fn try_lock_exclusive_until(&self, timeout: Self::Instant) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_exclusive_until(timeout))
+    }
+}
+
+unsafe impl<T> RawRwLockUpgradeDowngrade for TracingWrapper<T>
+where
+    T: RawRwLockUpgradeDowngrade,
+{
+    unsafe fn downgrade_upgradable(&self) {
+        self.inner.downgrade_upgradable()
+    }
+
+    unsafe fn downgrade_to_upgradable(&self) {
+        self.inner.downgrade_to_upgradable()
+    }
+}
+
+unsafe impl<T> RawRwLockUpgradeFair for TracingWrapper<T>
+where
+    T: RawRwLockUpgradeFair,
+{
+    unsafe fn unlock_upgradable_fair(&self) {
+        self.unlock(|| self.inner.unlock_upgradable_fair())
+    }
+
+    unsafe fn bump_upgradable(&self) {
+        self.inner.bump_upgradable()
+    }
+}
+
+unsafe impl<T> RawRwLockUpgradeTimed for TracingWrapper<T>
+where
+    T: RawRwLockUpgradeTimed,
+{
+    fn try_lock_upgradable_for(&self, timeout: Self::Duration) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_upgradable_for(timeout))
+    }
+
+    fn try_lock_upgradable_until(&self, timeout: Self::Instant) -> bool {
+        self.conditionally_lock(|| self.inner.try_lock_upgradable_until(timeout))
+    }
+
+    unsafe fn try_upgrade_for(&self, timeout: Self::Duration) -> bool {
+        self.inner.try_upgrade_for(timeout)
+    }
+
+    unsafe fn try_upgrade_until(&self, timeout: Self::Instant) -> bool {
+        self.inner.try_upgrade_until(timeout)
+    }
+}

src/parkinglot.rs

@@ -0,0 +1,296 @@
+//! Wrapper types and type aliases for tracing [`parking_lot`] mutexes.
+//!
+//! This module provides type aliases that use the [`lockapi`][crate::lockapi] module to provide
+//! tracing variants of the `parking_lot` primitives. Each of the `TracingX` type aliases wraps an
+//! `X` in the `parkint_lot` api with dependency tracking, and a `DebugX` will refer to a `TracingX`
+//! when  `debug_assertions` are enabled and to `X` when they're not. This can be used to aid
+//! debugging in development while enjoying maximum performance in production.
+//!
+//! # Usage
+//!
+//! ```
+//! # use std::sync::Arc;
+//! # use std::thread;
+//! # use lock_api::Mutex;
+//! # use tracing_mutex::parkinglot::TracingMutex;
+//! let mutex = Arc::new(TracingMutex::new(0));
+//!
+//! let handles: Vec<_> = (0..10).map(|_| {
+//!    let mutex = Arc::clone(&mutex);
+//!    thread::spawn(move || *mutex.lock() += 1)
+//! }).collect();
+//!
+//! handles.into_iter().for_each(|handle| handle.join().unwrap());
+//!
+//! // All threads completed so the value should be 10.
+//! assert_eq!(10, *mutex.lock());
+//! ```
+//!
+//! # Limitations
+//!
+//! The main lock for the global state is still provided by `std::sync` and the tracing primitives
+//! are larger than the `parking_lot` primitives they wrap, so there can be a performance
+//! degradation between using this and using `parking_lot` directly. If this is of concern to you,
+//! try using the `DebugX`-structs, which provide cycle detection only when `debug_assertions` are
+//! enabled and have no overhead when they're not.
+//!
+//! In addition, the mutex guards returned by the tracing wrappers are `!Send`, regardless of
+//! whether `parking_lot` is configured to have `Send` mutex guards. This is a limitation of the
+//! current bookkeeping system.
+use parking_lot::Once;
+use parking_lot::OnceState;
+
+use crate::lockapi::TracingWrapper;
+use crate::LazyMutexId;
+
+macro_rules! debug_variant {
+    ($debug_name:ident, $tracing_name:ident, $normal_name:ty) => {
+        type $tracing_name = TracingWrapper<$normal_name>;
+
+        #[cfg(debug_assertions)]
+        type $debug_name = TracingWrapper<$normal_name>;
+        #[cfg(not(debug_assertions))]
+        type $debug_name = $normal_name;
+    };
+}
+
+debug_variant!(
+    DebugRawFairMutex,
+    TracingRawFairMutex,
+    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>;
+/// Mutex guard for [`TracingFairMutex`].
+pub type TracingFairMutexGuard<'a, T> = lock_api::MutexGuard<'a, TracingRawFairMutex, T>;
+/// RAII guard for `TracingFairMutexGuard::map`.
+pub type TracingMappedFairMutexGuard<'a, T> =
+    lock_api::MappedMutexGuard<'a, TracingRawFairMutex, T>;
+/// Debug-only dependency tracking fair mutex.
+///
+/// If debug assertions are enabled this resolves to [`TracingFairMutex`] and to
+/// [`parking_lot::FairMutex`] otherwise.
+pub type DebugFairMutex<T> = lock_api::Mutex<DebugRawFairMutex, T>;
+/// Mutex guard for [`DebugFairMutex`].
+pub type DebugFairMutexGuard<'a, T> = lock_api::MutexGuard<'a, DebugRawFairMutex, T>;
+/// RAII guard for `DebugFairMutexGuard::map`.
+pub type DebugMappedFairMutexGuard<'a, T> = lock_api::MappedMutexGuard<'a, DebugRawFairMutex, T>;
+
+/// Dependency tracking mutex. See: [`parking_lot::Mutex`].
+pub type TracingMutex<T> = lock_api::Mutex<TracingRawMutex, T>;
+/// Mutex guard for [`TracingMutex`].
+pub type TracingMutexGuard<'a, T> = lock_api::MutexGuard<'a, TracingRawMutex, T>;
+/// RAII guard for `TracingMutexGuard::map`.
+pub type TracingMappedMutexGuard<'a, T> = lock_api::MappedMutexGuard<'a, TracingRawMutex, T>;
+/// Debug-only dependency tracking mutex.
+///
+/// If debug assertions are enabled this resolves to [`TracingMutex`] and to [`parking_lot::Mutex`]
+/// otherwise.
+pub type DebugMutex<T> = lock_api::Mutex<DebugRawMutex, T>;
+/// Mutex guard for [`DebugMutex`].
+pub type DebugMutexGuard<'a, T> = lock_api::MutexGuard<'a, DebugRawMutex, T>;
+/// RAII guard for `TracingMutexGuard::map`.
+pub type DebugMappedMutexGuard<'a, T> = lock_api::MappedMutexGuard<'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`].
+pub type TracingReentrantMutexGuard<'a, T> = lock_api::ReentrantMutexGuard<
+    'a,
+    TracingWrapper<parking_lot::RawMutex>,
+    parking_lot::RawThreadId,
+    T,
+>;
+/// RAII guard for `TracingReentrantMutexGuard::map`.
+pub type TracingMappedReentrantMutexGuard<'a, T> =
+    lock_api::MappedReentrantMutexGuard<'a, TracingRawMutex, parking_lot::RawThreadId, T>;
+
+/// Debug-only dependency tracking reentrant mutex.
+///
+/// If debug assertions are enabled this resolves to [`TracingReentrantMutex`] and to
+/// [`parking_lot::ReentrantMutex`] otherwise.
+pub type DebugReentrantMutex<T> =
+    lock_api::ReentrantMutex<DebugRawMutex, parking_lot::RawThreadId, T>;
+/// Mutex guard for [`DebugReentrantMutex`].
+pub type DebugReentrantMutexGuard<'a, T> =
+    lock_api::ReentrantMutexGuard<'a, DebugRawMutex, parking_lot::RawThreadId, T>;
+/// RAII guard for `DebugReentrantMutexGuard::map`.
+pub type DebugMappedReentrantMutexGuard<'a, T> =
+    lock_api::MappedReentrantMutexGuard<'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>;
+/// Upgradable Read guard for [`TracingRwLock`].
+pub type TracingRwLockUpgradableReadGuard<'a, T> =
+    lock_api::RwLockUpgradableReadGuard<'a, TracingRawRwLock, T>;
+/// Write guard for [`TracingRwLock`].
+pub type TracingRwLockWriteGuard<'a, T> = lock_api::RwLockWriteGuard<'a, TracingRawRwLock, T>;
+/// RAII guard for `TracingRwLockReadGuard::map`.
+pub type TracingMappedRwLockReadGuard<'a, T> =
+    lock_api::MappedRwLockReadGuard<'a, TracingRawRwLock, T>;
+/// RAII guard for `TracingRwLockWriteGuard::map`.
+pub type TracingMappedRwLockWriteGuard<'a, T> =
+    lock_api::MappedRwLockWriteGuard<'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>;
+/// Upgradable Read guard for [`TracingRwLock`].
+pub type DebugRwLockUpgradableReadGuard<'a, T> =
+    lock_api::RwLockUpgradableReadGuard<'a, DebugRawRwLock, T>;
+/// Write guard for [`TracingRwLock`].
+pub type DebugRwLockWriteGuard<'a, T> = lock_api::RwLockWriteGuard<'a, DebugRawRwLock, T>;
+/// RAII guard for `DebugRwLockReadGuard::map`.
+pub type DebugMappedRwLockReadGuard<'a, T> = lock_api::MappedRwLockReadGuard<'a, DebugRawRwLock, T>;
+/// RAII guard for `DebugRwLockWriteGuard::map`.
+pub type DebugMappedRwLockWriteGuard<'a, T> =
+    lock_api::MappedRwLockWriteGuard<'a, DebugRawRwLock, T>;
+
+/// A dependency-tracking wrapper for [`parking_lot::Once`].
+#[derive(Debug, Default)]
+pub struct TracingOnce {
+    inner: Once,
+    id: LazyMutexId,
+}
+
+impl TracingOnce {
+    /// Create a new `TracingOnce` value.
+    pub const fn new() -> Self {
+        Self {
+            inner: Once::new(),
+            id: LazyMutexId::new(),
+        }
+    }
+
+    /// Returns the current state of this `Once`.
+    pub fn state(&self) -> OnceState {
+        self.inner.state()
+    }
+
+    ///
+    /// This call is considered as "locking this `TracingOnce`" and it participates in dependency
+    /// tracking as such.
+    ///
+    /// # Panics
+    ///
+    /// This method will panic if `f` panics, poisoning this `Once`. In addition, this function
+    /// panics when the lock acquisition order is determined to be inconsistent.
+    pub fn call_once(&self, f: impl FnOnce()) {
+        let _borrow = self.id.get_borrowed();
+        self.inner.call_once(f);
+    }
+
+    /// Performs the given initialization routine once and only once.
+    ///
+    /// This method is identical to [`TracingOnce::call_once`] except it ignores poisoning.
+    pub fn call_once_force(&self, f: impl FnOnce(OnceState)) {
+        let _borrow = self.id.get_borrowed();
+        self.inner.call_once_force(f);
+    }
+}
+
+/// Debug-only `Once`.
+///
+/// If debug assertions are enabled this resolves to [`TracingOnce`] and to [`parking_lot::Once`]
+/// otherwise.
+#[cfg(debug_assertions)]
+pub type DebugOnce = TracingOnce;
+#[cfg(not(debug_assertions))]
+pub type DebugOnce = Once;
+
+#[cfg(test)]
+mod tests {
+    use std::sync::Arc;
+    use std::thread;
+
+    use super::*;
+
+    #[test]
+    fn test_mutex_usage() {
+        let mutex = Arc::new(TracingMutex::new(()));
+        let local_lock = mutex.lock();
+        drop(local_lock);
+
+        thread::spawn(move || {
+            let _remote_lock = mutex.lock();
+        })
+        .join()
+        .unwrap();
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_mutex_conflict() {
+        let mutexes = [
+            TracingMutex::new(()),
+            TracingMutex::new(()),
+            TracingMutex::new(()),
+        ];
+
+        for i in 0..3 {
+            let _first_lock = mutexes[i].lock();
+            let _second_lock = mutexes[(i + 1) % 3].lock();
+        }
+    }
+
+    #[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_rwlock_upgradable_read_usage() {
+        let lock = TracingRwLock::new(());
+
+        // Should be able to acquire an upgradable read lock.
+        let upgradable_guard: TracingRwLockUpgradableReadGuard<'_, _> = lock.upgradable_read();
+
+        // Should be able to upgrade the guard.
+        let _write_guard: TracingRwLockWriteGuard<'_, _> =
+            TracingRwLockUpgradableReadGuard::upgrade(upgradable_guard);
+    }
+
+    #[test]
+    fn test_once_usage() {
+        let once = Arc::new(TracingOnce::new());
+        let once_clone = once.clone();
+
+        assert!(!once_clone.state().done());
+
+        let handle = thread::spawn(move || {
+            assert!(!once_clone.state().done());
+
+            once_clone.call_once(|| {});
+
+            assert!(once_clone.state().done());
+        });
+
+        handle.join().unwrap();
+
+        assert!(once.state().done());
+    }
+}

src/stdsync.rs

@@ -16,6 +16,7 @@
 use std::fmt;
 use std::ops::Deref;
 use std::ops::DerefMut;
+use std::sync::Condvar;
 use std::sync::LockResult;
 use std::sync::Mutex;
 use std::sync::MutexGuard;
@@ -27,6 +28,8 @@ use std::sync::RwLockReadGuard;
 use std::sync::RwLockWriteGuard;
 use std::sync::TryLockError;
 use std::sync::TryLockResult;
+use std::sync::WaitTimeoutResult;
+use std::time::Duration;
 
 use crate::BorrowedMutex;
 use crate::LazyMutexId;
@@ -48,6 +51,14 @@ pub type DebugMutexGuard<'a, T> = TracingMutexGuard<'a, T>;
 #[cfg(not(debug_assertions))]
 pub type DebugMutexGuard<'a, T> = MutexGuard<'a, T>;
 
+/// Debug-only `Condvar`
+///
+/// Type alias that accepts the mutex guard emitted from [`DebugMutex`].
+#[cfg(debug_assertions)]
+pub type DebugCondvar = TracingCondvar;
+#[cfg(not(debug_assertions))]
+pub type DebugCondvar = Condvar;
+
 /// Debug-only tracing `RwLock`.
 ///
 /// Type alias that resolves to [`TracingRwLock`] when debug assertions are enabled and to
@@ -97,7 +108,7 @@ pub struct TracingMutex<T> {
 #[derive(Debug)]
 pub struct TracingMutexGuard<'a, T> {
     inner: MutexGuard<'a, T>,
-    mutex: BorrowedMutex<'a>,
+    _mutex: BorrowedMutex<'a>,
 }
 
 fn map_lockresult<T, I, F>(result: LockResult<I>, mapper: F) -> LockResult<T>
@@ -144,7 +155,7 @@ impl<T> TracingMutex<T> {
         let result = self.inner.lock();
 
         let mapper = |guard| TracingMutexGuard {
-            mutex,
+            _mutex: mutex,
             inner: guard,
         };
 
@@ -163,7 +174,7 @@ impl<T> TracingMutex<T> {
         let result = self.inner.try_lock();
 
         let mapper = |guard| TracingMutexGuard {
-            mutex,
+            _mutex: mutex,
             inner: guard,
         };
 
@@ -195,7 +206,7 @@ impl<T> From<T> for TracingMutex<T> {
 }
 
 impl<'a, T> Deref for TracingMutexGuard<'a, T> {
-    type Target = MutexGuard<'a, T>;
+    type Target = T;
 
     fn deref(&self) -> &Self::Target {
         &self.inner
@@ -214,6 +225,123 @@ impl<'a, T: fmt::Display> fmt::Display for TracingMutexGuard<'a, T> {
     }
 }
 
+/// Wrapper around [`std::sync::Condvar`].
+///
+/// Allows `TracingMutexGuard` to be used with a `Condvar`. Unlike other structs in this module,
+/// this wrapper does not add any additional dependency tracking or other overhead on top of the
+/// primitive it wraps. All dependency tracking happens through the mutexes itself.
+///
+/// # Panics
+///
+/// This struct does not add any panics over the base implementation of `Condvar`, but panics due to
+/// dependency tracking may poison associated mutexes.
+///
+/// # Examples
+///
+/// ```
+/// use std::sync::Arc;
+/// use std::thread;
+///
+/// use tracing_mutex::stdsync::{TracingCondvar, TracingMutex};
+///
+/// let pair = Arc::new((TracingMutex::new(false), TracingCondvar::new()));
+/// let pair2 = Arc::clone(&pair);
+///
+/// // Spawn a thread that will unlock the condvar
+/// thread::spawn(move || {
+///     let (lock, condvar) = &*pair2;
+///     *lock.lock().unwrap() = true;
+///     condvar.notify_one();
+/// });
+///
+/// // Wait until the thread unlocks the condvar
+/// let (lock, condvar) = &*pair;
+/// let guard = lock.lock().unwrap();
+/// let guard = condvar.wait_while(guard, |started| !*started).unwrap();
+///
+/// // Guard should read true now
+/// assert!(*guard);
+/// ```
+#[derive(Debug, Default)]
+pub struct TracingCondvar(Condvar);
+
+impl TracingCondvar {
+    /// Creates a new condition variable which is ready to be waited on and notified.
+    pub fn new() -> Self {
+        Default::default()
+    }
+
+    /// Wrapper for [`std::sync::Condvar::wait`].
+    pub fn wait<'a, T>(
+        &self,
+        guard: TracingMutexGuard<'a, T>,
+    ) -> LockResult<TracingMutexGuard<'a, T>> {
+        let TracingMutexGuard { _mutex, inner } = guard;
+
+        map_lockresult(self.0.wait(inner), |inner| TracingMutexGuard {
+            _mutex,
+            inner,
+        })
+    }
+
+    /// Wrapper for [`std::sync::Condvar::wait_while`].
+    pub fn wait_while<'a, T, F>(
+        &self,
+        guard: TracingMutexGuard<'a, T>,
+        condition: F,
+    ) -> LockResult<TracingMutexGuard<'a, T>>
+    where
+        F: FnMut(&mut T) -> bool,
+    {
+        let TracingMutexGuard { _mutex, inner } = guard;
+
+        map_lockresult(self.0.wait_while(inner, condition), |inner| {
+            TracingMutexGuard { _mutex, inner }
+        })
+    }
+
+    /// Wrapper for [`std::sync::Condvar::wait_timeout`].
+    pub fn wait_timeout<'a, T>(
+        &self,
+        guard: TracingMutexGuard<'a, T>,
+        dur: Duration,
+    ) -> LockResult<(TracingMutexGuard<'a, T>, WaitTimeoutResult)> {
+        let TracingMutexGuard { _mutex, inner } = guard;
+
+        map_lockresult(self.0.wait_timeout(inner, dur), |(inner, result)| {
+            (TracingMutexGuard { _mutex, inner }, result)
+        })
+    }
+
+    /// Wrapper for [`std::sync::Condvar::wait_timeout_while`].
+    pub fn wait_timeout_while<'a, T, F>(
+        &self,
+        guard: TracingMutexGuard<'a, T>,
+        dur: Duration,
+        condition: F,
+    ) -> LockResult<(TracingMutexGuard<'a, T>, WaitTimeoutResult)>
+    where
+        F: FnMut(&mut T) -> bool,
+    {
+        let TracingMutexGuard { _mutex, inner } = guard;
+
+        map_lockresult(
+            self.0.wait_timeout_while(inner, dur, condition),
+            |(inner, result)| (TracingMutexGuard { _mutex, inner }, result),
+        )
+    }
+
+    /// Wrapper for [`std::sync::Condvar::notify_one`].
+    pub fn notify_one(&self) {
+        self.0.notify_one();
+    }
+
+    /// Wrapper for [`std::sync::Condvar::notify_all`].
+    pub fn notify_all(&self) {
+        self.0.notify_all();
+    }
+}
+
 /// Wrapper for [`std::sync::RwLock`].
 #[derive(Debug, Default)]
 pub struct TracingRwLock<T> {
@@ -227,7 +355,7 @@ pub struct TracingRwLock<T> {
 #[derive(Debug)]
 pub struct TracingRwLockGuard<'a, L> {
     inner: L,
-    mutex: BorrowedMutex<'a>,
+    _mutex: BorrowedMutex<'a>,
 }
 
 /// Wrapper around [`std::sync::RwLockReadGuard`].
@@ -254,7 +382,10 @@ impl<T> TracingRwLock<T> {
         let mutex = self.id.get_borrowed();
         let result = self.inner.read();
 
-        map_lockresult(result, |inner| TracingRwLockGuard { inner, mutex })
+        map_lockresult(result, |inner| TracingRwLockGuard {
+            inner,
+            _mutex: mutex,
+        })
     }
 
     /// Wrapper for [`std::sync::RwLock::write`].
@@ -268,7 +399,10 @@ impl<T> TracingRwLock<T> {
         let mutex = self.id.get_borrowed();
         let result = self.inner.write();
 
-        map_lockresult(result, |inner| TracingRwLockGuard { inner, mutex })
+        map_lockresult(result, |inner| TracingRwLockGuard {
+            inner,
+            _mutex: mutex,
+        })
     }
 
     /// Wrapper for [`std::sync::RwLock::try_read`].
@@ -282,7 +416,10 @@ impl<T> TracingRwLock<T> {
         let mutex = self.id.get_borrowed();
         let result = self.inner.try_read();
 
-        map_trylockresult(result, |inner| TracingRwLockGuard { inner, mutex })
+        map_trylockresult(result, |inner| TracingRwLockGuard {
+            inner,
+            _mutex: mutex,
+        })
     }
 
     /// Wrapper for [`std::sync::RwLock::try_write`].
@@ -296,7 +433,10 @@ impl<T> TracingRwLock<T> {
         let mutex = self.id.get_borrowed();
         let result = self.inner.try_write();
 
-        map_trylockresult(result, |inner| TracingRwLockGuard { inner, mutex })
+        map_trylockresult(result, |inner| TracingRwLockGuard {
+            inner,
+            _mutex: mutex,
+        })
     }
 
     /// Return a mutable reference to the underlying data.
@@ -401,7 +541,12 @@ mod tests {
 
     #[test]
     fn test_mutex_usage() {
-        let mutex = Arc::new(TracingMutex::new(()));
+        let mutex = Arc::new(TracingMutex::new(0));
+
+        assert_eq!(*mutex.lock().unwrap(), 0);
+        *mutex.lock().unwrap() = 1;
+        assert_eq!(*mutex.lock().unwrap(), 1);
+
         let mutex_clone = mutex.clone();
 
         let _guard = mutex.lock().unwrap();
@@ -418,7 +563,14 @@ mod tests {
 
     #[test]
     fn test_rwlock_usage() {
-        let rwlock = Arc::new(TracingRwLock::new(()));
+        let rwlock = Arc::new(TracingRwLock::new(0));
+
+        assert_eq!(*rwlock.read().unwrap(), 0);
+        assert_eq!(*rwlock.write().unwrap(), 0);
+        *rwlock.write().unwrap() = 1;
+        assert_eq!(*rwlock.read().unwrap(), 1);
+        assert_eq!(*rwlock.write().unwrap(), 1);
+
         let rwlock_clone = rwlock.clone();
 
         let _read_lock = rwlock.read().unwrap();