Index: lldb/trunk/source/Host/common/MainLoop.cpp
===================================================================
--- lldb/trunk/source/Host/common/MainLoop.cpp
+++ lldb/trunk/source/Host/common/MainLoop.cpp
@@ -107,8 +107,14 @@
   num_events = kevent(loop.m_kqueue, in_events.data(), in_events.size(),
                       out_events, llvm::array_lengthof(out_events), nullptr);
 
-  if (num_events < 0)
-    return Status(errno, eErrorTypePOSIX);
+  if (num_events < 0) {
+    if (errno == EINTR) {
+      // in case of EINTR, let the main loop run one iteration
+      // we need to zero num_events to avoid assertions failing
+      num_events = 0;
+    } else
+      return Status(errno, eErrorTypePOSIX);
+  }
   return Status();
 }
 
Index: lldb/trunk/unittests/Host/MainLoopTest.cpp
===================================================================
--- lldb/trunk/unittests/Host/MainLoopTest.cpp
+++ lldb/trunk/unittests/Host/MainLoopTest.cpp
@@ -141,4 +141,28 @@
   ASSERT_TRUE(loop.Run().Success());
   ASSERT_EQ(1u, callback_count);
 }
+
+// Test that a signal which is not monitored by the MainLoop does not
+// cause a premature exit.
+TEST_F(MainLoopTest, UnmonitoredSignal) {
+  MainLoop loop;
+  Status error;
+  struct sigaction sa;
+  sa.sa_sigaction = [](int, siginfo_t *, void *) { };
+  sa.sa_flags = SA_SIGINFO; // important: no SA_RESTART
+  sigemptyset(&sa.sa_mask);
+  ASSERT_EQ(0, sigaction(SIGUSR2, &sa, nullptr));
+
+  auto handle = loop.RegisterSignal(SIGUSR1, make_callback(), error);
+  ASSERT_TRUE(error.Success());
+  std::thread killer([]() {
+    sleep(1);
+    kill(getpid(), SIGUSR2);
+    sleep(1);
+    kill(getpid(), SIGUSR1);
+  });
+  ASSERT_TRUE(loop.Run().Success());
+  killer.join();
+  ASSERT_EQ(1u, callback_count);
+}
 #endif