[compiler-rt] [TSan] Fix deadlocks during TSan error reporting on Apple platforms (PR #151495)

[Dan Blackwell via llvm-commits]

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@@ -2141,13 +2142,29 @@ static void ReportErrnoSpoiling(ThreadState *thr, uptr pc, int sig) {
   // StackTrace::GetNestInstructionPc(pc) is used because return address is
   // expected, OutputReport() will undo this.
   ObtainCurrentStack(thr, StackTrace::GetNextInstructionPc(pc), &stack);
-  ThreadRegistryLock l(&ctx->thread_registry);
-  ScopedReport rep(ReportTypeErrnoInSignal);
-  rep.SetSigNum(sig);
-  if (!IsFiredSuppression(ctx, ReportTypeErrnoInSignal, stack)) {
-    rep.AddStack(stack, true);
-    OutputReport(thr, rep);
+  ScopedReport *rep = (ScopedReport *)__builtin_alloca(sizeof(ScopedReport));
+  bool suppressed;
+  // Take a new scope as Apple platforms require the below locks released
+  // before symbolizing in order to avoid a deadlock
+  {
+    ThreadRegistryLock l(&ctx->thread_registry);
+    new (rep) ScopedReport(ReportTypeErrnoInSignal);
+    rep->SetSigNum(sig);
+    suppressed = IsFiredSuppression(ctx, ReportTypeErrnoInSignal, stack);
+    if (!suppressed)
+      rep->AddStack(stack, true);
+#if SANITIZER_APPLE
+  }  // Close this scope to release the locks before writing report
+  if (!suppressed)
+    OutputReport(thr, *rep);
+#else
+    if (!suppressed)
+      OutputReport(thr, *rep);
   }
+#endif
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DanBlackwell wrote:

I've changed it to this, made the alignment correct for non-Apple platforms. I think it's worth it to make sure that any future changes get applied to all platforms (I know it's easy to miss code that's greyed out behind an ifdef in the editor)

https://github.com/llvm/llvm-project/pull/151495