diff --git a/llvm/lib/Transforms/Instrumentation/RealtimeSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/RealtimeSanitizer.cpp
index 7854cf4f2c625..b977badc9d6c1 100644
--- a/llvm/lib/Transforms/Instrumentation/RealtimeSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/RealtimeSanitizer.cpp
@@ -45,6 +45,26 @@ static void insertCallAtAllFunctionExitPoints(Function &Fn,
         insertCallBeforeInstruction(Fn, I, InsertFnName);
 }
 
+static PreservedAnalyses rtsanPreservedCFGAnalyses() {
+  PreservedAnalyses PA;
+  PA.preserveSet<CFGAnalyses>();
+  return PA;
+}
+
+static void insertExpectNotRealtimeAtFunctionEntryPoint(Function &F) {
+  IRBuilder<> Builder(&F.front().front());
+  Value *NameArg = Builder.CreateGlobalString(F.getName());
+
+  FunctionType *FuncType =
+      FunctionType::get(Type::getVoidTy(F.getContext()),
+                        {PointerType::getUnqual(F.getContext())}, false);
+
+  FunctionCallee Func = F.getParent()->getOrInsertFunction(
+      "__rtsan_expect_not_realtime", FuncType);
+
+  Builder.CreateCall(Func, {NameArg});
+}
+
 RealtimeSanitizerPass::RealtimeSanitizerPass(
     const RealtimeSanitizerOptions &Options) {}
 
@@ -53,10 +73,12 @@ PreservedAnalyses RealtimeSanitizerPass::run(Function &F,
   if (F.hasFnAttribute(Attribute::SanitizeRealtime)) {
     insertCallAtFunctionEntryPoint(F, "__rtsan_realtime_enter");
     insertCallAtAllFunctionExitPoints(F, "__rtsan_realtime_exit");
+    return rtsanPreservedCFGAnalyses();
+  }
 
-    PreservedAnalyses PA;
-    PA.preserveSet<CFGAnalyses>();
-    return PA;
+  if (F.hasFnAttribute(Attribute::SanitizeRealtimeUnsafe)) {
+    insertExpectNotRealtimeAtFunctionEntryPoint(F);
+    return rtsanPreservedCFGAnalyses();
   }
 
   return PreservedAnalyses::all();
diff --git a/llvm/test/Instrumentation/RealtimeSanitizer/rtsan_unsafe.ll b/llvm/test/Instrumentation/RealtimeSanitizer/rtsan_unsafe.ll
new file mode 100644
index 0000000000000..646a9a0e22e21
--- /dev/null
+++ b/llvm/test/Instrumentation/RealtimeSanitizer/rtsan_unsafe.ll
@@ -0,0 +1,16 @@
+; RUN: opt < %s -passes=rtsan -S | FileCheck %s
+
+define void @blocking_function() #0 {
+  ret void
+}
+
+define noundef i32 @main() #2 {
+  call void @blocking_function() #4
+  ret i32 0
+}
+
+attributes #0 = { mustprogress noinline sanitize_realtime_unsafe optnone ssp uwtable(sync) }
+
+; RealtimeSanitizer pass should insert __rtsan_expect_not_realtime at function entrypoint
+; CHECK-LABEL: @blocking_function()
+; CHECK-NEXT: call{{.*}}@__rtsan_expect_not_realtime({{ptr .*}})