[perf] Fix a data race in the PerfJITEventListener

[ezhulenev]

Summary

Concurrent JIT compilation + PerfJITEventListener triggers tsan error

[ezhulenev]

Update

llvm/lib/ExecutionEngine/PerfJITEvents/PerfJITEventListener.cpp

for (const std::pair<SymbolRef, uint64_t> &P : computeSymbolSizes(DebugObj)) {
     // corresonding code load.
     DILineInfoTable Lines = Context->getLineInfoForAddressRange(
         {*AddrOrErr, SectionIndex}, Size, FileLineInfoKind::AbsoluteFilePath);
 
     NotifyDebug(*AddrOrErr, Lines);
     NotifyCode(Name, *AddrOrErr, Size);
   }
 
+  // avoid races with writes
+  std::lock_guard<sys::Mutex> Guard(Mutex);
+
   Dumpstream->flush();
 }
 
 void PerfJITEventListener::notifyFreeingObject(ObjectKey K) {
   // perf currently doesn't have an interface for unloading. But munmap()ing the
   // code section does, so that's ok.
 }