  This technical report contains material accompanying our work with same title
published at ASPLOS'21. We start in Sec. 1 with a detailed presentation of the
core innovation of this work, Await Model Checking (AMC). The correctness
proofs of AMC can be found in Sec. 2. Next, we discuss three study cases in
Sec. 3, presenting bugs found and challenges encountered when applying VSync to
existing code bases. Finally, in Sec. 4 we describe the setup details of our
evaluation and report further experimental results.
