[all-commits] [llvm/llvm-project] 576f3f: Make DWARFContext more thread safe.

[Greg Clayton via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 576f3f0cc930dc9aee157b76dd80319dfe7d51b9
      https://github.com/llvm/llvm-project/commit/576f3f0cc930dc9aee157b76dd80319dfe7d51b9
  Author: Greg Clayton <gclayton at fb.com>
  Date:   2023-09-01 (Fri, 01 Sep 2023)

  Changed paths:
    M llvm/include/llvm/DebugInfo/DWARF/DWARFContext.h
    M llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
    M llvm/tools/llvm-gsymutil/llvm-gsymutil.cpp

  Log Message:
  -----------
  Make DWARFContext more thread safe.

llvm-gsymutil uses a DWARFContext from multiple threads as it parses each compile unit. As it finds issues it might end up dumping a DIE to an output stream which can cause accesses to the DWARFContext from multiple threads. In llvm-gsymutil it can end up dumping a DIE from multiple threads into thread specific stream which was causing DWARFContext::getTUIndex() to be called and can crash the process.

This fix puts a recursive mutex into the DWARFContext class and makes most APIs threadsafe for access. Many of the methods in DWARFContext will check if a member variable has been filled in yet, and parse what is needed and populate a member variagle with the results. Now a mutex protects these functions.

Differential Revision: https://reviews.llvm.org/D157459