[lldb] [MainLoop] Add kevent() EINTR handling

Add missing EINTR handling for kevent() calls.  If the call is
interrupted, return from Poll() as if zero events were returned and let
the polling resume on next iteration.  This fixes test flakiness
on NetBSD.

Includes a test case suggested by Pavel Labath on D42206.

Differential Revision: https://reviews.llvm.org/D58230

llvm-svn: 354122

diff --git a/lldb/source/Host/common/MainLoop.cpp b/lldb/source/Host/common/MainLoop.cpp
index 9bb5bfe..a480393 100644 (file)
--- a/lldb/source/Host/common/MainLoop.cpp
+++ b/lldb/source/Host/common/MainLoop.cpp
@@ -107,8 +107,14 @@ Status MainLoop::RunImpl::Poll() {
   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();
 }
 

diff --git a/lldb/unittests/Host/MainLoopTest.cpp b/lldb/unittests/Host/MainLoopTest.cpp
index b6aff2f..af225de 100644 (file)
--- a/lldb/unittests/Host/MainLoopTest.cpp
+++ b/lldb/unittests/Host/MainLoopTest.cpp
@@ -141,4 +141,28 @@ TEST_F(MainLoopTest, Signal) {
   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