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// Copyright 2018 Google LLC
//
// 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 <atomic>
#include "gtest/gtest.h"
#include "absl/strings/string_view.h"
#include "absl/time/clock.h"
#include "absl/time/time.h"
#include "test/util/test_util.h"
#include "test/util/thread_util.h"
namespace gvisor {
namespace testing {
namespace {
// Test that a thread that never yields to the OS does not prevent other threads
// from running.
TEST(ConcurrencyTest, SingleProcessMultithreaded) {
std::atomic<int> a(0);
ScopedThread t([&a]() {
while (!a.load()) {
}
});
absl::SleepFor(absl::Seconds(1));
// We are still able to execute code in this thread. The other hasn't
// permanently hung execution in both threads.
a.store(1);
}
// Test that multiple threads in this process continue to execute in parallel,
// even if an unrelated second process is spawned.
TEST(ConcurrencyTest, MultiProcessMultithreaded) {
// In PID 1, start TIDs 1 and 2, and put both to sleep.
//
// Start PID 3, which spins for 5 seconds, then exits.
//
// TIDs 1 and 2 wake and attempt to Activate, which cannot occur until PID 3
// exits.
//
// Both TIDs 1 and 2 should be woken. If they are not both woken, the test
// hangs.
//
// This is all fundamentally racy. If we are failing to wake all threads, the
// expectation is that this test becomes flaky, rather than consistently
// failing.
//
// If additional background threads fail to block, we may never schedule the
// child, at which point this test effectively becomes
// MultiProcessConcurrency. That's not expected to occur.
std::atomic<int> a(0);
ScopedThread t([&a]() {
// Block so that PID 3 can execute and we can wait on its exit.
absl::SleepFor(absl::Seconds(1));
while (!a.load()) {
}
});
pid_t child_pid;
ASSERT_THAT(child_pid = fork(), SyscallSucceeds());
if (child_pid == 0) {
// Busy wait without making any blocking syscalls.
auto end = absl::Now() + absl::Seconds(5);
while (absl::Now() < end) {
}
_exit(0);
}
absl::SleepFor(absl::Seconds(1));
// If only TID 1 is woken, thread.Join will hang.
// If only TID 2 is woken, both will hang.
a.store(1);
t.Join();
int status = 0;
EXPECT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0), SyscallSucceeds());
EXPECT_TRUE(WIFEXITED(status));
EXPECT_EQ(WEXITSTATUS(status), 0);
}
// Test that multiple processes can execute concurrently, even if one process
// never yields.
TEST(ConcurrencyTest, MultiProcessConcurrency) {
pid_t child_pid;
ASSERT_THAT(child_pid = fork(), SyscallSucceeds());
if (child_pid == 0) {
while (true) {
}
__builtin_unreachable();
}
absl::SleepFor(absl::Seconds(5));
// We are still able to execute code in this process. The other hasn't
// permanently hung execution in both processes.
ASSERT_THAT(kill(child_pid, SIGKILL), SyscallSucceeds());
int status = 0;
ASSERT_THAT(RetryEINTR(waitpid)(child_pid, &status, 0), SyscallSucceeds());
ASSERT_TRUE(WIFSIGNALED(status));
ASSERT_EQ(WTERMSIG(status), SIGKILL);
}
} // namespace
} // namespace testing
} // namespace gvisor
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