1 // Copyright 2021 Google LLC
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 #include "fcp/base/reentrancy_guard.h"
16
17 #include <atomic>
18
19 #include "gtest/gtest.h"
20 #include "absl/synchronization/notification.h"
21 #include "fcp/base/monitoring.h"
22 #include "fcp/base/scheduler.h"
23 #include "fcp/testing/testing.h"
24
25 namespace fcp {
26 namespace {
27
28 class ReentrancyGuardTest : public testing::Test {
29 protected:
SimpleMethod()30 Status SimpleMethod() {
31 ReentrancyGuard guard;
32 return guard.Check(&in_use_);
33 }
34
ReentrantMethod()35 Status ReentrantMethod() {
36 ReentrancyGuard guard;
37 FCP_RETURN_IF_ERROR((guard.Check(&in_use_)));
38 return ReentrantMethod();
39 }
40
LongRunningMethod(absl::Notification * method_entered,absl::Notification * resume)41 Status LongRunningMethod(absl::Notification* method_entered,
42 absl::Notification* resume) {
43 ReentrancyGuard guard;
44 FCP_RETURN_IF_ERROR((guard.Check(&in_use_)));
45 method_entered->Notify();
46 resume->WaitForNotification();
47 return FCP_STATUS(OK);
48 }
49
50 private:
51 std::atomic<bool> in_use_ = false;
52 };
53
TEST_F(ReentrancyGuardTest,SequentialCallsSucceed)54 TEST_F(ReentrancyGuardTest, SequentialCallsSucceed) {
55 ASSERT_THAT(SimpleMethod(), IsOk());
56 ASSERT_THAT(SimpleMethod(), IsOk());
57 }
58
TEST_F(ReentrancyGuardTest,ReentrantCallsFail)59 TEST_F(ReentrancyGuardTest, ReentrantCallsFail) {
60 ASSERT_THAT(ReentrantMethod(), IsCode(FAILED_PRECONDITION));
61 }
62
TEST_F(ReentrancyGuardTest,ConcurrentCallsFail)63 TEST_F(ReentrancyGuardTest, ConcurrentCallsFail) {
64 absl::Notification long_running_method_entered;
65 absl::Notification resume;
66
67 auto pool = fcp::CreateThreadPoolScheduler(1);
68 pool->Schedule([&] {
69 ASSERT_THAT(LongRunningMethod(&long_running_method_entered, &resume),
70 IsOk());
71 });
72
73 // This signals that LongRunningMethod() has been entered and waits there
74 // to be resumed.
75 long_running_method_entered.WaitForNotification();
76
77 // Make a concurrent call, which is expected to fail.
78 ASSERT_THAT(SimpleMethod(), IsCode(FAILED_PRECONDITION));
79
80 // Resume LongRunningMethod() and wait for the thread to finish.
81 resume.Notify();
82 pool->WaitUntilIdle();
83 }
84
85 } // namespace
86 } // namespace fcp
87