1 files changed, 6 insertions, 2 deletions
diff --git a/llvm/lib/Support/ErrorHandling.cpp b/llvm/lib/Support/ErrorHandling.cpp
index 342c4f0..b9e4eab 100644
--- a/llvm/lib/Support/ErrorHandling.cpp
+++ b/llvm/lib/Support/ErrorHandling.cpp
@@ -23,6 +23,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include <cassert>
 #include <cstdlib>
+#include <mutex>
 
 #if defined(HAVE_UNISTD_H)
 # include <unistd.h>
@@ -37,16 +38,18 @@ using namespace llvm;
 static fatal_error_handler_t ErrorHandler = nullptr;
 static void *ErrorHandlerUserData = nullptr;
 
+static llvm::recursive_mutex ErrorHandlerMutex;
+
 void llvm::install_fatal_error_handler(fatal_error_handler_t handler,
                                        void *user_data) {
-  assert(!llvm_is_multithreaded() &&
-         "Cannot register error handlers after starting multithreaded mode!\n");
+  std::lock_guard<llvm::recursive_mutex> Lock(ErrorHandlerMutex);
   assert(!ErrorHandler && "Error handler already registered!\n");
   ErrorHandler = handler;
   ErrorHandlerUserData = user_data;
 }
 
 void llvm::remove_fatal_error_handler() {
+  std::lock_guard<llvm::recursive_mutex> Lock(ErrorHandlerMutex);
   ErrorHandler = nullptr;
 }
 
@@ -63,6 +66,7 @@ void llvm::report_fatal_error(StringRef Reason, bool GenCrashDiag) {
 }
 
 void llvm::report_fatal_error(const Twine &Reason, bool GenCrashDiag) {
+  std::lock_guard<llvm::recursive_mutex> Lock(ErrorHandlerMutex);
   if (ErrorHandler) {
     ErrorHandler(ErrorHandlerUserData, Reason.str(), GenCrashDiag);
   } else {