only read lock transform cache

Author: Wumpf

crates/viewer/re_view_spatial/src/caches/transform_database_store.rs

@@ -1,4 +1,4 @@
-use parking_lot::{ArcMutexGuard, Mutex, RawMutex};
+use parking_lot::{ArcRwLockReadGuard, RawRwLock, RwLock};
 use std::sync::Arc;
 
 use re_chunk_store::ChunkStoreEvent;
@@ -12,25 +12,25 @@ use re_viewer_context::{Cache, CacheMemoryReport};
 #[derive(Default)]
 pub struct TransformDatabaseStoreCache {
     initialized: bool,
-    transform_cache: Arc<Mutex<TransformResolutionCache>>,
+    transform_cache: Arc<RwLock<TransformResolutionCache>>,
 }
 
 impl TransformDatabaseStoreCache {
     /// Gets access to the transform cache.
     ///
     /// If the cache was newly added, will make sure that all existing chunks in the entity db are processed.
-    pub fn lock_transform_cache(
+    pub fn read_lock_transform_cache(
         &mut self,
         entity_db: &EntityDb,
-    ) -> ArcMutexGuard<RawMutex, TransformResolutionCache> {
+    ) -> ArcRwLockReadGuard<RawRwLock, TransformResolutionCache> {
         if !self.initialized {
-            self.initialized = true;
+            self.initialized = true; // There can't be a race here since we have `&mut self``.
             self.transform_cache
-                .lock()
+                .write()
                 .add_chunks(entity_db.storage_engine().store().iter_chunks());
         }
 
-        self.transform_cache.lock_arc()
+        self.transform_cache.read_arc()
     }
 }
 
@@ -57,12 +57,12 @@ impl Cache for TransformDatabaseStoreCache {
         re_tracing::profile_function!();
 
         debug_assert!(
-            self.transform_cache.try_lock().is_some(),
+            self.transform_cache.try_write().is_some(),
             "Transform cache is still locked on processing store events. This should never happen."
         );
 
         self.transform_cache
-            .lock()
+            .write()
             .process_store_events(events.iter().copied());
     }
 

crates/viewer/re_view_spatial/src/contexts/transform_tree_context.rs

@@ -152,8 +152,9 @@ impl ViewContextSystem for TransformTreeContext {
         ctx: &re_viewer_context::ViewerContext<'_>,
     ) -> ViewContextSystemOncePerFrameResult {
         let caches = ctx.store_context.caches;
-        let transform_cache = caches
-            .entry(|c: &mut TransformDatabaseStoreCache| c.lock_transform_cache(ctx.recording()));
+        let transform_cache = caches.entry(|c: &mut TransformDatabaseStoreCache| {
+            c.read_lock_transform_cache(ctx.recording())
+        });
 
         let transform_forest =
             re_tf::TransformForest::new(ctx.recording(), &transform_cache, &ctx.current_query());
@@ -218,10 +219,9 @@ impl ViewContextSystem for TransformTreeContext {
         self.transform_infos = {
             re_tracing::profile_scope!("transform info lookup");
 
-            // TODO: bad locking.
             let caches = ctx.viewer_ctx.store_context.caches;
             let transform_cache = caches.entry(|c: &mut TransformDatabaseStoreCache| {
-                c.lock_transform_cache(ctx.recording())
+                c.read_lock_transform_cache(ctx.recording())
             });
             let transforms = transform_cache.transforms_for_timeline(query.timeline);