[vm/shared] Introduce tag_table_lock to ensure data-race-safe access to tag_table.

Fixes #61404
TEST=tsan ci

Change-Id: I606a6fde54b7948bce206cb3d13d9534e50019ab
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/447003
Reviewed-by: Ryan Macnak <[email protected]>
Commit-Queue: Alexander Aprelev <[email protected]>

Author: aam

runtime/vm/isolate.cc

@@ -364,6 +364,7 @@ IsolateGroup::IsolateGroup(std::shared_ptr<IsolateGroupSource> source,
       cache_mutex_(),
       handler_info_cache_(),
       catch_entry_moves_cache_(),
+      tag_table_lock_(),
       tag_table_(GrowableObjectArray::null()) {
   FlagsCopyFrom(api_flags);
   if (!is_vm_isolate) {

runtime/vm/isolate.h

@@ -847,6 +847,7 @@ class IsolateGroup : public IntrusiveDListEntry<IsolateGroup> {
     has_attempted_stepping_.store(value, std::memory_order_relaxed);
   }
 
+  SafepointRwLock* tag_table_lock() { return &tag_table_lock_; }
   GrowableObjectArrayPtr tag_table() const { return tag_table_; }
   void set_tag_table(const GrowableObjectArray& value);
 
@@ -1008,6 +1009,7 @@ class IsolateGroup : public IntrusiveDListEntry<IsolateGroup> {
 
   std::atomic<bool> has_attempted_stepping_;
 
+  SafepointRwLock tag_table_lock_;
   GrowableObjectArrayPtr tag_table_;
 };
 

runtime/vm/object.cc

@@ -27783,8 +27783,18 @@ UserTagPtr UserTag::New(Thread* thread,
                         const String& label,
                         Heap::Space space) {
   auto isolate_group = thread->isolate_group();
-  ASSERT(isolate_group->tag_table() != GrowableObjectArray::null());
   // Canonicalize by name.
+  {
+    SafepointReadRwLocker ml(thread, isolate_group->tag_table_lock());
+    ASSERT(isolate_group->tag_table() != GrowableObjectArray::null());
+    UserTag& result =
+        UserTag::Handle(FindTagInIsolateGroup(isolate_group, thread, label));
+    if (!result.IsNull()) {
+      // Tag already exists, return existing instance.
+      return result.ptr();
+    }
+  }
+  SafepointWriteRwLocker mlw(thread, isolate_group->tag_table_lock());
   UserTag& result =
       UserTag::Handle(FindTagInIsolateGroup(isolate_group, thread, label));
   if (!result.IsNull()) {
@@ -27806,7 +27816,6 @@ UserTagPtr UserTag::New(Thread* thread,
 }
 
 UserTagPtr UserTag::DefaultTag(Thread* thread) {
-  //   Thread* thread = Thread::Current();
   Zone* zone = thread->zone();
   if (thread->default_tag() != UserTag::null()) {
     // Already created.
@@ -27843,11 +27852,6 @@ UserTagPtr UserTag::FindTagInIsolateGroup(IsolateGroup* isolate_group,
   return UserTag::null();
 }
 
-UserTagPtr UserTag::FindTagInIsolateGroup(Thread* thread, const String& label) {
-  auto isolate_group = thread->isolate_group();
-  return FindTagInIsolateGroup(isolate_group, thread, label);
-}
-
 void UserTag::AddTagToIsolateGroup(Thread* thread, const UserTag& tag) {
   auto isolate_group = thread->isolate_group();
   Zone* zone = thread->zone();

runtime/vm/object.h

@@ -13391,7 +13391,6 @@ class UserTag : public Instance {
   static UserTagPtr FindTagInIsolateGroup(IsolateGroup* isolate_group,
                                           Thread* thread,
                                           const String& label);
-  static UserTagPtr FindTagInIsolateGroup(Thread* thread, const String& label);
 
  private:
   static void AddTagToIsolateGroup(Thread* thread, const UserTag& tag);