1 files changed, 151 insertions, 0 deletions
diff --git a/test/syscalls/linux/sigstop.cc b/test/syscalls/linux/sigstop.cc
new file mode 100644
index 000000000..b2fcedd62
--- /dev/null
+++ b/test/syscalls/linux/sigstop.cc
@@ -0,0 +1,151 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <signal.h>
+#include <stdlib.h>
+#include <sys/select.h>
+
+#include "gtest/gtest.h"
+#include "absl/flags/flag.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+#include "test/util/multiprocess_util.h"
+#include "test/util/posix_error.h"
+#include "test/util/test_util.h"
+#include "test/util/thread_util.h"
+
+ABSL_FLAG(bool, sigstop_test_child, false,
+          "If true, run the SigstopTest child workload.");
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+constexpr absl::Duration kChildStartupDelay = absl::Seconds(5);
+constexpr absl::Duration kChildMainThreadDelay = absl::Seconds(10);
+constexpr absl::Duration kChildExtraThreadDelay = absl::Seconds(15);
+constexpr absl::Duration kPostSIGSTOPDelay = absl::Seconds(20);
+
+// Comparisons on absl::Duration aren't yet constexpr (2017-07-14), so we
+// can't just use static_assert.
+TEST(SigstopTest, TimesAreRelativelyConsistent) {
+  EXPECT_LT(kChildStartupDelay, kChildMainThreadDelay)
+      << "Child process will exit before the parent process attempts to stop "
+         "it";
+  EXPECT_LT(kChildMainThreadDelay, kChildExtraThreadDelay)
+      << "Secondary thread in child process will exit before main thread, "
+         "causing it to exit with the wrong code";
+  EXPECT_LT(kChildExtraThreadDelay, kPostSIGSTOPDelay)
+      << "Parent process stops waiting before child process may exit if "
+         "improperly stopped, rendering the test ineffective";
+}
+
+// Exit codes communicated from the child workload to the parent test process.
+constexpr int kChildMainThreadExitCode = 10;
+constexpr int kChildExtraThreadExitCode = 11;
+
+TEST(SigstopTest, Correctness) {
+  pid_t child_pid = -1;
+  int execve_errno = 0;
+  auto cleanup = ASSERT_NO_ERRNO_AND_VALUE(
+      ForkAndExec("/proc/self/exe", {"/proc/self/exe", "--sigstop_test_child"},
+                  {}, nullptr, &child_pid, &execve_errno));
+
+  ASSERT_GT(child_pid, 0);
+  ASSERT_EQ(execve_errno, 0);
+
+  // Wait for the child subprocess to start the second thread before stopping
+  // it.
+  absl::SleepFor(kChildStartupDelay);
+  ASSERT_THAT(kill(child_pid, SIGSTOP), SyscallSucceeds());
+  int status;
+  EXPECT_THAT(RetryEINTR(waitpid)(child_pid, &status, WUNTRACED),
+              SyscallSucceedsWithValue(child_pid));
+  EXPECT_TRUE(WIFSTOPPED(status));
+  EXPECT_EQ(SIGSTOP, WSTOPSIG(status));
+
+  // Sleep for longer than either of the sleeps in the child subprocess,
+  // expecting the child to stay alive because it's stopped.
+  absl::SleepFor(kPostSIGSTOPDelay);
+  ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, WNOHANG),
+              SyscallSucceedsWithValue(0));
+
+  // Resume the child.
+  ASSERT_THAT(kill(child_pid, SIGCONT), SyscallSucceeds());
+
+  EXPECT_THAT(RetryEINTR(waitpid)(child_pid, &status, WCONTINUED),
+              SyscallSucceedsWithValue(child_pid));
+  EXPECT_TRUE(WIFCONTINUED(status));
+
+  // Expect it to die.
+  ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0), SyscallSucceeds());
+  ASSERT_TRUE(WIFEXITED(status));
+  ASSERT_EQ(WEXITSTATUS(status), kChildMainThreadExitCode);
+}
+
+// Like base:SleepFor, but tries to avoid counting time spent stopped due to a
+// stop signal toward the sleep.
+//
+// This is required due to an inconsistency in how nanosleep(2) and stop signals
+// interact on Linux. When nanosleep is interrupted, it writes the remaining
+// time back to its second timespec argument, so that if nanosleep is
+// interrupted by a signal handler then userspace can immediately call nanosleep
+// again with that timespec. However, if nanosleep is automatically restarted
+// (because it's interrupted by a signal that is not delivered to a handler,
+// such as a stop signal), it's restarted based on the timer's former *absolute*
+// expiration time (via ERESTART_RESTARTBLOCK => SYS_restart_syscall =>
+// hrtimer_nanosleep_restart). This means that time spent stopped is effectively
+// counted as time spent sleeping, resulting in less time spent sleeping than
+// expected.
+//
+// Dividing the sleep into multiple smaller sleeps limits the impact of this
+// effect to the length of each sleep during which a stop occurs; for example,
+// if a sleeping process is only stopped once, SleepIgnoreStopped can
+// under-sleep by at most 100ms.
+void SleepIgnoreStopped(absl::Duration d) {
+  absl::Duration const max_sleep = absl::Milliseconds(100);
+  while (d > absl::ZeroDuration()) {
+    absl::Duration to_sleep = std::min(d, max_sleep);
+    absl::SleepFor(to_sleep);
+    d -= to_sleep;
+  }
+}
+
+void RunChild() {
+  // Start another thread that attempts to call exit_group with a different
+  // error code, in order to verify that SIGSTOP stops this thread as well.
+  ScopedThread t([] {
+    SleepIgnoreStopped(kChildExtraThreadDelay);
+    exit(kChildExtraThreadExitCode);
+  });
+  SleepIgnoreStopped(kChildMainThreadDelay);
+  exit(kChildMainThreadExitCode);
+}
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor
+
+int main(int argc, char** argv) {
+  gvisor::testing::TestInit(&argc, &argv);
+
+  if (absl::GetFlag(FLAGS_sigstop_test_child)) {
+    gvisor::testing::RunChild();
+    return 1;
+  }
+
+  return gvisor::testing::RunAllTests();
+}