[core] fix SharedObjectRegistry crash for accessing dict from multith…

…reads (expo#25997)

# Why

fix the crash from https://github.com/ospfranco/expo-sqlite-benchmark

# How

the hermes gc thread may be different to js thread. we should protect
the internal data structures with thread-safety. this pr added a
DispatchQueue to protect the internal data structures.

# Test Plan

test repro on https://github.com/ospfranco/expo-sqlite-benchmark

packages/expo-modules-core/CHANGELOG.md

@@ -8,6 +8,8 @@
 
 ### 🐛 Bug fixes
 
+- [iOS] Fixed `SharedObjectRegistry` crash for accessing internal data structures from multi-threads. ([#25997](https://github.com/expo/expo/pull/25997) by [@kudo](https://github.com/kudo))
+
 ### 💡 Others
 
 ## 1.11.2 — 2023-12-15

packages/expo-modules-core/ios/SharedObjects/SharedObjectRegistry.swift

@@ -31,28 +31,39 @@ public final class SharedObjectRegistry {
    */
   internal static var pairs = [SharedObjectId: SharedObjectPair]()
 
+  /**
+   The lock queue to keep thread safety for internal data structures.
+   */
+  private static let lockQueue = DispatchQueue(label: "expo.modules.core.SharedObjectRegistry")
+
   /**
    A number of all pairs stored in the registry.
    */
   internal static var size: Int {
-    return pairs.count
+    return Self.lockQueue.sync {
+      return pairs.count
+    }
   }
 
   /**
    Returns the next shared object ID and increases the counter.
    */
   @discardableResult
   internal static func pullNextId() -> SharedObjectId {
-    let id = nextId
-    nextId += 1
-    return id
+    return Self.lockQueue.sync {
+      let id = nextId
+      nextId += 1
+      return id
+    }
   }
 
   /**
    Returns a pair of shared objects with given ID or `nil` when there is no such pair in the registry.
    */
   internal static func get(_ id: SharedObjectId) -> SharedObjectPair? {
-    return pairs[id]
+    return Self.lockQueue.sync {
+      return pairs[id]
+    }
   }
 
   /**
@@ -70,7 +81,10 @@ public final class SharedObjectRegistry {
     jsObject.setObjectDeallocator { delete(id) }
 
     // Save the pair in the dictionary.
-    pairs[id] = (native: nativeObject, javaScript: jsObject.createWeak())
+    let jsWeakObject = jsObject.createWeak()
+    Self.lockQueue.async {
+      pairs[id] = (native: nativeObject, javaScript: jsWeakObject)
+    }
 
     return id
   }
@@ -79,12 +93,14 @@ public final class SharedObjectRegistry {
    Deletes the shared objects pair with a given ID.
    */
   internal static func delete(_ id: SharedObjectId) {
-    if let pair = pairs[id] {
-      // Reset an ID on the objects.
-      pair.native.sharedObjectId = 0
-
-      // Delete the pair from the dictionary.
-      pairs[id] = nil
+    Self.lockQueue.async {
+      if let pair = pairs[id] {
+        // Reset an ID on the objects.
+        pair.native.sharedObjectId = 0
+
+        // Delete the pair from the dictionary.
+        pairs[id] = nil
+      }
     }
   }
 
@@ -93,7 +109,9 @@ public final class SharedObjectRegistry {
    */
   internal static func toNativeObject(_ jsObject: JavaScriptObject) -> SharedObject? {
     if let objectId = try? jsObject.getProperty(sharedObjectIdPropertyName).asInt() {
-      return pairs[objectId]?.native
+      return Self.lockQueue.sync {
+        return pairs[objectId]?.native
+      }
     }
     return nil
   }
@@ -103,7 +121,9 @@ public final class SharedObjectRegistry {
    */
   internal static func toJavaScriptObject(_ nativeObject: SharedObject) -> JavaScriptObject? {
     let objectId = nativeObject.sharedObjectId
-    return pairs[objectId]?.javaScript.lock()
+    return Self.lockQueue.sync {
+      return pairs[objectId]?.javaScript.lock()
+    }
   }
 
   /**
@@ -127,6 +147,8 @@ public final class SharedObjectRegistry {
   }
 
   internal static func clear() {
-    pairs.removeAll()
+    Self.lockQueue.async {
+      pairs.removeAll()
+    }
   }
 }

packages/expo-modules-core/ios/Tests/SharedObjectRegistrySpec.swift

@@ -68,7 +68,7 @@ final class SharedObjectRegistrySpec: ExpoSpec {
         let nativeObject = TestSharedObject()
         let id = SharedObjectRegistry.add(native: nativeObject, javaScript: runtime.createObject())
         SharedObjectRegistry.delete(id)
-        expect(nativeObject.sharedObjectId) == 0
+        expect(nativeObject.sharedObjectId).toEventually(equal(0))
       }
     }