libc/test/integration/src/threads/call_once_test.cpp

   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
  22 static constexpr unsigned int NUM_THREADS = 5;
  23 static LIBC_NAMESPACE::cpp::Atomic<unsigned int> thread_count;
  24
  25 static unsigned int call_count;
  26 static void call_once_func() { ++call_count; }
  27
  28 static 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
  37 void 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
  59 static mtx_t once_func_blocker;
  60 static void blocking_once_func() {
  61   LIBC_NAMESPACE::mtx_lock(&once_func_blocker);
  62   LIBC_NAMESPACE::mtx_unlock(&once_func_blocker);
  63 }
  64
  65 static LIBC_NAMESPACE::cpp::Atomic<unsigned int> start_count;
  66 static LIBC_NAMESPACE::cpp::Atomic<unsigned int> done_count;
  67 static 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.
  78 void 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
 117 TEST_MAIN() {
 118   call_from_5_threads();
 119   test_synchronization();
 120   return 0;
 121 }