Bump the generation when a read promotes an LRUCache entry

src/internal/linked_list.rs

@@ -571,6 +571,17 @@ impl<T> Cursor<T> {
         unsafe { list.push_front_node(links) };
     }
 
+    /// Returns `true` if the node this cursor points to is the last node of `list`.
+    ///
+    /// # Safety
+    ///
+    /// Same contract as [`move_to_front`](Self::move_to_front).
+    #[inline]
+    pub unsafe fn is_back(&self, list: &LinkedList<T>) -> bool {
+        // SAFETY: the sentinel is always valid; caller guarantees the node is linked.
+        unsafe { (*list.sentinel.as_ptr()).prev == self.links().as_ptr() }
+    }
+
     /// Moves the node this cursor points to the back of `list`.
     ///
     /// # Safety

src/policies/fifopolicy.rs

@@ -255,6 +255,7 @@ impl PolicyExt for FIFOPolicy {
         &mut self,
         py: pyo3::Python,
         key: &<Self::Handle as HandleExt>::Key,
+        _shared: &Self::Shared,
     ) -> pyo3::PyResult<Option<&Self::Handle>> {
         let eq = |index: &usize| get_handle!(&self, *index).key().py_eq(py, key);
         match self.table.get(key.hash(), eq)? {

src/policies/lfupolicy.rs

@@ -320,6 +320,7 @@ impl PolicyExt for LFUPolicy {
         &mut self,
         py: pyo3::Python,
         key: &<Self::Handle as HandleExt>::Key,
+        _shared: &Self::Shared,
     ) -> pyo3::PyResult<Option<&Self::Handle>> {
         let cursor = self
             .table

src/policies/lrupolicy.rs

@@ -169,6 +169,7 @@ impl PolicyExt for LRUPolicy {
         &mut self,
         py: pyo3::Python,
         key: &<Self::Handle as HandleExt>::Key,
+        shared: &Self::Shared,
     ) -> pyo3::PyResult<Option<&Self::Handle>> {
         unsafe {
             let bucket = self
@@ -177,7 +178,13 @@ impl PolicyExt for LRUPolicy {
 
             match bucket {
                 Some(cursor) => {
-                    cursor.move_to_back(&mut self.list);
+                    // moving the entry is a mutation, so it bumps the generation like
+                    // any other; a hit on the most recent entry moves nothing
+                    if !cursor.is_back(&self.list) {
+                        shared.generation_version().increment();
+                        cursor.move_to_back(&mut self.list);
+                    }
+
                     Ok(Some(cursor.element()))
                 }
                 None => Ok(None),

src/policies/nopolicy.rs

@@ -134,6 +134,7 @@ impl PolicyExt for NoPolicy {
         &mut self,
         py: pyo3::Python,
         key: &<Self::Handle as HandleExt>::Key,
+        _shared: &Self::Shared,
     ) -> pyo3::PyResult<Option<&Self::Handle>> {
         let bucket = self.table.find(key.hash(), |x| key.py_eq(py, x.key()))?;
         Ok(bucket.map(|x| unsafe { x.as_ref() }))

src/policies/rrpolicy.rs

@@ -136,6 +136,7 @@ impl PolicyExt for RRPolicy {
         &mut self,
         py: pyo3::Python,
         key: &<Self::Handle as HandleExt>::Key,
+        _shared: &Self::Shared,
     ) -> pyo3::PyResult<Option<&Self::Handle>> {
         let bucket = self.table.find(key.hash(), |x| key.py_eq(py, x.key()))?;
         Ok(bucket.map(|x| unsafe { x.as_ref() }))

src/policies/traits.rs

@@ -105,6 +105,7 @@ pub trait PolicyExt: Sized {
         &mut self,
         py: pyo3::Python,
         key: &<Self::Handle as HandleExt>::Key,
+        shared: &Self::Shared,
     ) -> pyo3::PyResult<Option<&Self::Handle>>;
 
     /// Returns a [`PolicyEntry`] for the slot at `hash` / `eq`.

src/policies/ttlpolicy.rs

@@ -369,6 +369,7 @@ impl PolicyExt for TTLPolicy {
         &mut self,
         py: pyo3::Python,
         key: &<Self::Handle as HandleExt>::Key,
+        _shared: &Self::Shared,
     ) -> pyo3::PyResult<Option<&Self::Handle>> {
         let eq = |index: &usize| get_handle!(&self, *index).key().py_eq(py, key);
 

src/policies/vttlpolicy.rs

@@ -311,6 +311,7 @@ impl PolicyExt for VTTLPolicy {
         &mut self,
         py: pyo3::Python,
         key: &<Self::Handle as HandleExt>::Key,
+        _shared: &Self::Shared,
     ) -> pyo3::PyResult<Option<&Self::Handle>> {
         let cursor = self
             .table

src/policies/wrapped.rs

@@ -112,7 +112,7 @@ impl<P: PolicyExt> Wrapped<P> {
     ) -> pyo3::PyResult<bool> {
         let mut lock = self.inner.lock();
 
-        let handle = lock.get(py, key)?;
+        let handle = lock.get(py, key, &self.shared)?;
         Ok(handle.is_some())
     }
 

src/pyclasses/cache.rs

@@ -279,7 +279,7 @@ impl PyCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -302,7 +302,7 @@ impl PyCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        match policy.get(py, &key)? {
+        match policy.get(py, &key, inner.shared())? {
             Some(x) => Ok(x.value().clone_ref(py)),
             None => Err(new_py_error!(
                 PyKeyError,
@@ -334,7 +334,7 @@ impl PyCache {
         let shared = inner.shared();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -383,7 +383,7 @@ impl PyCache {
         {
             let mut policy = inner.policy();
 
-            if let Some(x) = policy.get(py, &key)? {
+            if let Some(x) = policy.get(py, &key, inner.shared())? {
                 return Ok(x.value().clone_ref(py));
             }
         }
@@ -393,7 +393,7 @@ impl PyCache {
 
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 

src/pyclasses/fifocache.rs

@@ -285,7 +285,7 @@ impl PyFIFOCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -308,7 +308,7 @@ impl PyFIFOCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        match policy.get(py, &key)? {
+        match policy.get(py, &key, inner.shared())? {
             Some(x) => Ok(x.value().clone_ref(py)),
             None => Err(new_py_error!(
                 PyKeyError,
@@ -340,7 +340,7 @@ impl PyFIFOCache {
         let shared = inner.shared();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -389,7 +389,7 @@ impl PyFIFOCache {
         {
             let mut policy = inner.policy();
 
-            if let Some(x) = policy.get(py, &key)? {
+            if let Some(x) = policy.get(py, &key, inner.shared())? {
                 return Ok(x.value().clone_ref(py));
             }
         }
@@ -399,7 +399,7 @@ impl PyFIFOCache {
 
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 

src/pyclasses/lfucache.rs

@@ -303,7 +303,7 @@ impl PyLFUCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -326,7 +326,7 @@ impl PyLFUCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        match policy.get(py, &key)? {
+        match policy.get(py, &key, inner.shared())? {
             Some(x) => Ok(x.value().clone_ref(py)),
             None => Err(new_py_error!(
                 PyKeyError,
@@ -358,7 +358,7 @@ impl PyLFUCache {
         let shared = inner.shared();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -408,7 +408,7 @@ impl PyLFUCache {
         {
             let mut policy = inner.policy();
 
-            if let Some(x) = policy.get(py, &key)? {
+            if let Some(x) = policy.get(py, &key, inner.shared())? {
                 return Ok(x.value().clone_ref(py));
             }
         }
@@ -418,7 +418,7 @@ impl PyLFUCache {
 
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 

src/pyclasses/lrucache.rs

@@ -312,7 +312,7 @@ impl PyLRUCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -335,7 +335,7 @@ impl PyLRUCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        match policy.get(py, &key)? {
+        match policy.get(py, &key, inner.shared())? {
             Some(x) => Ok(x.value().clone_ref(py)),
             None => Err(new_py_error!(
                 PyKeyError,
@@ -367,7 +367,7 @@ impl PyLRUCache {
         let shared = inner.shared();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -416,7 +416,7 @@ impl PyLRUCache {
         {
             let mut policy = inner.policy();
 
-            if let Some(x) = policy.get(py, &key)? {
+            if let Some(x) = policy.get(py, &key, inner.shared())? {
                 return Ok(x.value().clone_ref(py));
             }
         }
@@ -426,7 +426,7 @@ impl PyLRUCache {
 
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 

src/pyclasses/rrcache.rs

@@ -283,7 +283,7 @@ impl PyRRCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -306,7 +306,7 @@ impl PyRRCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        match policy.get(py, &key)? {
+        match policy.get(py, &key, inner.shared())? {
             Some(x) => Ok(x.value().clone_ref(py)),
             None => Err(new_py_error!(
                 PyKeyError,
@@ -338,7 +338,7 @@ impl PyRRCache {
         let shared = inner.shared();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -387,7 +387,7 @@ impl PyRRCache {
         {
             let mut policy = inner.policy();
 
-            if let Some(x) = policy.get(py, &key)? {
+            if let Some(x) = policy.get(py, &key, inner.shared())? {
                 return Ok(x.value().clone_ref(py));
             }
         }
@@ -397,7 +397,7 @@ impl PyRRCache {
 
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 

src/pyclasses/ttlcache.rs

@@ -288,7 +288,7 @@ impl PyTTLCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -311,7 +311,7 @@ impl PyTTLCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        match policy.get(py, &key)? {
+        match policy.get(py, &key, inner.shared())? {
             Some(x) => Ok(x.value().clone_ref(py)),
             None => Err(new_py_error!(
                 PyKeyError,
@@ -343,7 +343,7 @@ impl PyTTLCache {
         let shared = inner.shared();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -393,7 +393,7 @@ impl PyTTLCache {
         {
             let mut policy = inner.policy();
 
-            if let Some(x) = policy.get(py, &key)? {
+            if let Some(x) = policy.get(py, &key, inner.shared())? {
                 return Ok(x.value().clone_ref(py));
             }
         }
@@ -403,7 +403,7 @@ impl PyTTLCache {
 
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             return Ok(x.value().clone_ref(py));
         }
 
@@ -724,7 +724,7 @@ impl PyTTLCache {
         let inner = self.0.get();
         let mut policy = inner.policy();
 
-        if let Some(x) = policy.get(py, &key)? {
+        if let Some(x) = policy.get(py, &key, inner.shared())? {
             let dur = x
                 .expires_at()
                 .duration_since(std::time::SystemTime::now())