llvm-project

186fac33 - Convert the StackFrameList mutex to a shared mutex. (#117252)

Convert the StackFrameList mutex to a shared mutex. (#117252) In fact, there's only one public API in StackFrameList that changes the list explicitly. The rest only change the list if you happen to ask for more frames than lldb has currently fetched and that always adds frames "behind the user's back". So we were much more prone to deadlocking than we needed to be. This patch uses a shared_mutex instead, and when we have to add more frames (in GetFramesUpTo) we switches to exclusive long enough to add the frames, then goes back to shared. Most of the work here was actually getting the stack frame list locking to not require a recursive mutex (shared mutexes aren't recursive). I also added a test that has 5 threads progressively asking for more frames simultaneously to make sure we get back valid frames and don't deadlock.