Implement the invalidate_entries_if method (WIP)

- Refactoring on the background invalidation task.
- Add Sync bounds to a generic parameter S of sync and future caches,
    so now all K, V and S have the following bounds:
    - Send + Sync + 'static

src/future/builder.rs

@@ -78,7 +78,7 @@ where
     /// Builds a `Cache<K, V, S>`, with the given `hasher`.
     pub fn build_with_hasher<S>(self, hasher: S) -> Cache<K, V, S>
     where
-        S: BuildHasher + Clone + Send + 'static,
+        S: BuildHasher + Clone + Send + Sync + 'static,
     {
         Cache::with_everything(
             self.max_capacity,

src/future/cache.rs

@@ -228,7 +228,7 @@ impl<K, V, S> Cache<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Clone + Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     pub(crate) fn with_everything(
         max_capacity: usize,
@@ -368,7 +368,7 @@ impl<K, V, S> ConcurrentCacheExt<K, V> for Cache<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     fn sync(&self) {
         self.base.inner.sync(MAX_SYNC_REPEATS);
@@ -380,7 +380,7 @@ impl<K, V, S> Cache<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Clone + Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     async fn insert_with_hash(&self, key: K, hash: u64, value: V) {
         let op = self.base.do_insert_with_hash(key, hash, value);
@@ -447,7 +447,7 @@ impl<K, V, S> Cache<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     fn reconfigure_for_testing(&mut self) {
         self.base.reconfigure_for_testing();

src/sync/base_cache.rs

@@ -80,7 +80,7 @@ impl<K, V, S> BaseCache<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Clone + Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     pub(crate) fn new(
         max_capacity: usize,
@@ -211,7 +211,7 @@ impl<K, V, S> BaseCache<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Clone + Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     #[inline]
     fn record_read_op(&self, op: ReadOp<K, V>) -> Result<(), TrySendError<ReadOp<K, V>>> {
@@ -314,7 +314,7 @@ impl<K, V, S> BaseCache<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     pub(crate) fn is_empty(&self) -> bool {
         self.inner.len() == 0
@@ -519,7 +519,7 @@ impl<K, V, S> InnerSync for Inner<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     fn sync(&self, max_repeats: usize) -> Option<SyncPace> {
         const EVICTION_BATCH_SIZE: usize = 500;
@@ -573,7 +573,7 @@ impl<K, V, S> Inner<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     fn apply_reads(&self, deqs: &mut Deques<K>, count: usize) {
         use ReadOp::*;

src/sync/builder.rs

@@ -104,7 +104,7 @@ where
     /// calling this method.
     pub fn build_with_hasher<S>(self, hasher: S) -> Cache<K, V, S>
     where
-        S: BuildHasher + Clone + Send + 'static,
+        S: BuildHasher + Clone + Send + Sync + 'static,
     {
         Cache::with_everything(
             self.max_capacity,
@@ -143,7 +143,7 @@ where
     /// calling this method.
     pub fn build_with_hasher<S>(self, hasher: S) -> SegmentedCache<K, V, S>
     where
-        S: BuildHasher + Clone + Send + 'static,
+        S: BuildHasher + Clone + Send + Sync + 'static,
     {
         SegmentedCache::with_everything(
             self.max_capacity,

src/sync/cache.rs

@@ -207,7 +207,7 @@ impl<K, V, S> Cache<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Clone + Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     pub(crate) fn with_everything(
         max_capacity: usize,
@@ -331,7 +331,7 @@ impl<K, V, S> ConcurrentCacheExt<K, V> for Cache<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     fn sync(&self) {
         self.base.inner.sync(MAX_SYNC_REPEATS);
@@ -343,7 +343,7 @@ impl<K, V, S> Cache<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Clone + Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     #[inline]
     fn schedule_write_op(
@@ -378,7 +378,7 @@ impl<K, V, S> Cache<K, V, S>
 where
     K: Hash + Eq + Send + Sync + 'static,
     V: Send + Sync + 'static,
-    S: BuildHasher + Clone + Send + 'static,
+    S: BuildHasher + Clone + Send + Sync + 'static,
 {
     pub(crate) fn reconfigure_for_testing(&mut self) {
         self.base.reconfigure_for_testing();