Add new reset_dependencies API

src/lib.rs

@@ -99,6 +99,7 @@ pub mod lockapi;
 pub mod parkinglot;
 mod reporting;
 pub mod stdsync;
+pub mod util;
 
 thread_local! {
     /// Stack to track which locks are held

src/lockapi.rs

@@ -23,7 +23,9 @@ use lock_api::RawRwLockUpgradeDowngrade;
 use lock_api::RawRwLockUpgradeFair;
 use lock_api::RawRwLockUpgradeTimed;
 
+use crate::util::PrivateTraced;
 use crate::LazyMutexId;
+use crate::MutexId;
 
 /// Tracing wrapper for all [`lock_api`] traits.
 ///
@@ -86,6 +88,12 @@ impl<T> TracingWrapper<T> {
     }
 }
 
+impl<T> PrivateTraced for TracingWrapper<T> {
+    fn get_id(&self) -> &MutexId {
+        &self.id
+    }
+}
+
 unsafe impl<T> RawMutex for TracingWrapper<T>
 where
     T: RawMutex,

src/stdsync/tracing.rs

@@ -10,6 +10,7 @@ use std::sync::TryLockResult;
 use std::sync::WaitTimeoutResult;
 use std::time::Duration;
 
+use crate::util::PrivateTraced;
 use crate::BorrowedMutex;
 use crate::LazyMutexId;
 
@@ -127,6 +128,12 @@ impl<T> Mutex<T> {
     }
 }
 
+impl<T> PrivateTraced for Mutex<T> {
+    fn get_id(&self) -> &crate::MutexId {
+        &self.id
+    }
+}
+
 impl<T> From<T> for Mutex<T> {
     fn from(t: T) -> Self {
         Self::new(t)
@@ -375,6 +382,12 @@ impl<T> RwLock<T> {
     }
 }
 
+impl<T> PrivateTraced for RwLock<T> {
+    fn get_id(&self) -> &crate::MutexId {
+        &self.id
+    }
+}
+
 impl<T> From<T> for RwLock<T> {
     fn from(t: T) -> Self {
         Self::new(t)
@@ -455,6 +468,12 @@ impl Once {
     }
 }
 
+impl PrivateTraced for Once {
+    fn get_id(&self) -> &crate::MutexId {
+        &self.mutex_id
+    }
+}
+
 /// Wrapper for [`std::sync::OnceLock`]
 ///
 /// The exact locking behaviour of [`std::sync::OnceLock`] is currently undefined, but may
@@ -553,6 +572,12 @@ impl<T> OnceLock<T> {
     }
 }
 
+impl<T> PrivateTraced for OnceLock<T> {
+    fn get_id(&self) -> &crate::MutexId {
+        &self.id
+    }
+}
+
 impl<T> Default for OnceLock<T> {
     #[inline]
     fn default() -> Self {

src/util.rs

@@ -0,0 +1,59 @@
+use crate::MutexId;
+
+/// Reset the dependencies for the given entity.
+///
+/// # Performance
+///
+/// This function locks the dependency graph to remove the item from it. This is an `O(E)` operation
+/// with `E` being the number of dependencies directly associated with this particular instance. As
+/// such, it is not advisable to call this method from a hot loop.
+///
+/// # Safety
+///
+/// Use of this method invalidates the deadlock prevention guarantees that this library makes. As
+/// such, it should only be used when it is absolutely certain this will not introduce deadlocks
+/// later.
+///
+/// Other than deadlocks, no undefined behaviour can result from the use of this function.
+///
+/// # Example
+///
+/// ```
+/// use tracing_mutex::stdsync::Mutex;
+/// use tracing_mutex::util;
+///
+/// let first = Mutex::new(());
+/// let second = Mutex::new(());
+///
+/// {
+///     let _first_lock = first.lock().unwrap();
+///     second.lock().unwrap();
+/// }
+///
+/// // Reset the dependencies for the first mutex
+/// unsafe { util::reset_dependencies(&first) };
+///
+/// // Now we can unlock the mutexes in the opposite order without a panic.
+/// let _second_lock = second.lock().unwrap();
+/// first.lock().unwrap();
+/// ```
+pub unsafe fn reset_dependencies<T: Traced>(traced: &T) {
+    crate::get_dependency_graph().remove_node(traced.get_id().value());
+}
+
+/// Types that participate in dependency tracking
+///
+/// This trait is a public marker trait and is automatically implemented fore all types that
+/// implement the internal dependency tracking features.
+#[allow(private_bounds)]
+pub trait Traced: PrivateTraced {}
+
+impl<T: PrivateTraced> Traced for T {}
+
+/// Private implementation of the traced marker.
+///
+/// This trait is private (and seals the outer trait) to avoid exposing the MutexId type.
+pub(crate) trait PrivateTraced {
+    /// Get the mutex id associated with this traced item.
+    fn get_id(&self) -> &MutexId;
+}