1//===-- Tests for call_once -----------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "src/__support/CPP/atomic.h"
10#include "src/threads/call_once.h"
11#include "src/threads/mtx_destroy.h"
12#include "src/threads/mtx_init.h"
13#include "src/threads/mtx_lock.h"
14#include "src/threads/mtx_unlock.h"
15#include "src/threads/thrd_create.h"
16#include "src/threads/thrd_join.h"
17
18#include "test/IntegrationTest/test.h"
19
20#include <threads.h>
21
22static constexpr unsigned int NUM_THREADS = 5;
23static LIBC_NAMESPACE::cpp::Atomic<unsigned int> thread_count;
24
25static unsigned int call_count;
26static void call_once_func() { ++call_count; }
27
28static int func(void *) {
29 static once_flag flag = ONCE_FLAG_INIT;
30 LIBC_NAMESPACE::call_once(&flag, call_once_func);
31
32 thread_count.fetch_add(1);
33
34 return 0;
35}
36
37void call_from_5_threads() {
38 // Ensure the call count and thread count are 0 to begin with.
39 call_count = 0;
40 thread_count = 0;
41
42 thrd_t threads[NUM_THREADS];
43 for (unsigned int i = 0; i < NUM_THREADS; ++i) {
44 ASSERT_EQ(LIBC_NAMESPACE::thrd_create(threads + i, func, nullptr),
45 static_cast<int>(thrd_success));
46 }
47
48 for (unsigned int i = 0; i < NUM_THREADS; ++i) {
49 int retval;
50 ASSERT_EQ(LIBC_NAMESPACE::thrd_join(threads[i], &retval),
51 static_cast<int>(thrd_success));
52 ASSERT_EQ(retval, 0);
53 }
54
55 EXPECT_EQ(thread_count.val, 5U);
56 EXPECT_EQ(call_count, 1U);
57}
58
59static mtx_t once_func_blocker;
60static void blocking_once_func() {
61 LIBC_NAMESPACE::mtx_lock(&once_func_blocker);
62 LIBC_NAMESPACE::mtx_unlock(&once_func_blocker);
63}
64
65static LIBC_NAMESPACE::cpp::Atomic<unsigned int> start_count;
66static LIBC_NAMESPACE::cpp::Atomic<unsigned int> done_count;
67static int once_func_caller(void *) {
68 static once_flag flag;
69 start_count.fetch_add(1);
70 LIBC_NAMESPACE::call_once(&flag, blocking_once_func);
71 done_count.fetch_add(1);
72 return 0;
73}
74
75// Test the synchronization aspect of the call_once function.
76// This is not a fool proof test, but something which might be
77// useful when we add a flakiness detection scheme to UnitTest.
78void test_synchronization() {
79 start_count = 0;
80 done_count = 0;
81
82 ASSERT_EQ(LIBC_NAMESPACE::mtx_init(&once_func_blocker, mtx_plain),
83 static_cast<int>(thrd_success));
84 // Lock the blocking mutex so that the once func blocks.
85 ASSERT_EQ(LIBC_NAMESPACE::mtx_lock(&once_func_blocker),
86 static_cast<int>(thrd_success));
87
88 thrd_t t1, t2;
89 ASSERT_EQ(LIBC_NAMESPACE::thrd_create(&t1, once_func_caller, nullptr),
90 static_cast<int>(thrd_success));
91 ASSERT_EQ(LIBC_NAMESPACE::thrd_create(&t2, once_func_caller, nullptr),
92 static_cast<int>(thrd_success));
93
94 while (start_count.load() != 2)
95 ; // Spin until both threads start.
96
97 // Since the once func is blocked, the threads should not be done yet.
98 EXPECT_EQ(done_count.val, 0U);
99
100 // Unlock the blocking mutex so that the once func blocks.
101 ASSERT_EQ(LIBC_NAMESPACE::mtx_unlock(&once_func_blocker),
102 static_cast<int>(thrd_success));
103
104 int retval;
105 ASSERT_EQ(LIBC_NAMESPACE::thrd_join(t1, &retval),
106 static_cast<int>(thrd_success));
107 ASSERT_EQ(retval, 0);
108 ASSERT_EQ(LIBC_NAMESPACE::thrd_join(t2, &retval),
109 static_cast<int>(thrd_success));
110 ASSERT_EQ(retval, 0);
111
112 ASSERT_EQ(done_count.val, 2U);
113
114 LIBC_NAMESPACE::mtx_destroy(&once_func_blocker);
115}
116
117TEST_MAIN() {
118 call_from_5_threads();
119 test_synchronization();
120 return 0;
121}
122

source code of libc/test/integration/src/threads/call_once_test.cpp