[compiler-rt] TSAN: Report when thread is not live and referenced in pthread (PR #156921)

[Vitaly Buka via llvm-commits]

================
@@ -274,6 +274,11 @@ void ThreadRegistry::JoinThread(u32 tid, void *arg) {
     {
       ThreadRegistryLock l(this);
       ThreadContextBase *tctx = threads_[tid];
+
+      if (!tctx) {
----------------
vitalybuka wrote:

Because we like smaller changes, when I read the title, the impression was that you want add move verbose message to the CHECK failure.
But looks like you are fixing stuff as well.

So I guess better to
1. patch for message
2. patch for the fix, but this one needs some explanation why it's mode, not links # to issues




https://github.com/llvm/llvm-project/pull/156921