[sanitizer] Lock/Unlock stack store on fork

compiler-rt/lib/sanitizer_common/sanitizer_stack_store.h

public:
   uptr Allocated() const;
 
   // Packs all blocks which don't expect any more writes. A block is going to be
   // packed once. As soon trace from that block was requested, it will unpack
   // and stay unpacked after that.
   // Returns the number of released bytes.
   uptr Pack(Compression type);
 
+  void LockAll();
+  void UnlockAll();
+
   void TestOnlyUnmap();
 
  private:
   friend class StackStoreTest;
   static constexpr uptr GetBlockIdx(uptr frame_idx) {
     return frame_idx / kBlockSizeFrames;
   }
 
private:
    public:
     uptr *Get() const;
     uptr *GetOrCreate(StackStore *store);
     uptr *GetOrUnpack(StackStore *store);
     uptr Pack(Compression type, StackStore *store);
     void TestOnlyUnmap(StackStore *store);
     bool Stored(uptr n);
     bool IsPacked() const;
+    void Lock() NO_THREAD_SAFETY_ANALYSIS { mtx_.Lock(); }
+    void Unlock() NO_THREAD_SAFETY_ANALYSIS { mtx_.Unlock(); }
   };
 
   BlockInfo blocks_[kBlockCount] = {};
 };
 
 }  // namespace __sanitizer
 
 #endif  // SANITIZER_STACK_STORE_H

compiler-rt/lib/sanitizer_common/sanitizer_stack_store.cpp

 }
 
 uptr StackStore::Pack(Compression type) {
   uptr res = 0;
   for (BlockInfo &b : blocks_) res += b.Pack(type, this);
   return res;
 }
 
+void StackStore::LockAll() {
+  for (BlockInfo &b : blocks_) b.Lock();
+}
+
+void StackStore::UnlockAll() {
+  for (BlockInfo &b : blocks_) b.Unlock();
+}
+
 void StackStore::TestOnlyUnmap() {
   for (BlockInfo &b : blocks_) b.TestOnlyUnmap(this);
   internal_memset(this, 0, sizeof(*this));
 }
 
 uptr *StackStore::BlockInfo::Get() const {
   // Idiomatic double-checked locking uses memory_order_acquire here. But
   // relaxed is fine for us, justification is similar to

compiler-rt/lib/sanitizer_common/sanitizer_stackdepot.cpp

 }
 
 StackTrace StackDepotGet(u32 id) {
   return theDepot.Get(id);
 }
 
 void StackDepotLockAll() {
   theDepot.LockAll();
+  stackStore.LockAll();
 }
 
 void StackDepotUnlockAll() {
+  stackStore.UnlockAll();
   theDepot.UnlockAll();
 }
 
 void StackDepotPrintAll() {
 #if !SANITIZER_GO
   theDepot.PrintAll();
 #endif
 }