libc/test/integration/src/pthread/pthread_once_test.cpp

   1 //===-- Tests for pthread_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/pthread/pthread_create.h"
  11 #include "src/pthread/pthread_join.h"
  12 #include "src/pthread/pthread_mutex_destroy.h"
  13 #include "src/pthread/pthread_mutex_init.h"
  14 #include "src/pthread/pthread_mutex_lock.h"
  15 #include "src/pthread/pthread_mutex_unlock.h"
  16 #include "src/pthread/pthread_once.h"
  17
  18 #include "test/IntegrationTest/test.h"
  19
  20 #include <pthread.h>
  21 #include <stdint.h> // uintptr_t
  22
  23 static constexpr unsigned int NUM_THREADS = 5;
  24 static LIBC_NAMESPACE::cpp::Atomic<unsigned int> thread_count;
  25
  26 static unsigned int call_count;
  27 static void pthread_once_func() { ++call_count; }
  28
  29 static void *func(void *) {
  30   static pthread_once_t flag = PTHREAD_ONCE_INIT;
  31   ASSERT_EQ(LIBC_NAMESPACE::pthread_once(&flag, pthread_once_func), 0);
  32
  33   thread_count.fetch_add(1);
  34
  35   return nullptr;
  36 }
  37
  38 void call_from_5_threads() {
  39   // Ensure the call count and thread count are 0 to begin with.
  40   call_count = 0;
  41   thread_count = 0;
  42
  43   pthread_t threads[NUM_THREADS];
  44   for (unsigned int i = 0; i < NUM_THREADS; ++i) {
  45     ASSERT_EQ(
  46         LIBC_NAMESPACE::pthread_create(threads + i, nullptr, func, nullptr), 0);
  47   }
  48
  49   for (unsigned int i = 0; i < NUM_THREADS; ++i) {
  50     void *retval;
  51     ASSERT_EQ(LIBC_NAMESPACE::pthread_join(threads[i], &retval), 0);
  52     ASSERT_EQ(uintptr_t(retval), uintptr_t(0));
  53   }
  54
  55   EXPECT_EQ(thread_count.val, 5U);
  56   EXPECT_EQ(call_count, 1U);
  57 }
  58
  59 static pthread_mutex_t once_func_blocker;
  60 static void blocking_once_func() {
  61   LIBC_NAMESPACE::pthread_mutex_lock(&once_func_blocker);
  62   LIBC_NAMESPACE::pthread_mutex_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 void *once_func_caller(void *) {
  68   static pthread_once_t flag;
  69   start_count.fetch_add(1);
  70   LIBC_NAMESPACE::pthread_once(&flag, blocking_once_func);
  71   done_count.fetch_add(1);
  72   return nullptr;
  73 }
  74
  75 // Test the synchronization aspect of the pthread_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::pthread_mutex_init(&once_func_blocker, nullptr), 0);
  83   // Lock the blocking mutex so that the once func blocks.
  84   ASSERT_EQ(LIBC_NAMESPACE::pthread_mutex_lock(&once_func_blocker), 0);
  85
  86   pthread_t t1, t2;
  87   ASSERT_EQ(
  88       LIBC_NAMESPACE::pthread_create(&t1, nullptr, once_func_caller, nullptr),
  89       0);
  90   ASSERT_EQ(
  91       LIBC_NAMESPACE::pthread_create(&t2, nullptr, once_func_caller, nullptr),
  92       0);
  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::pthread_mutex_unlock(&once_func_blocker), 0);
 102
 103   void *retval;
 104   ASSERT_EQ(LIBC_NAMESPACE::pthread_join(t1, &retval), uintptr_t(0));
 105   ASSERT_EQ(uintptr_t(retval), 0);
 106   ASSERT_EQ(LIBC_NAMESPACE::pthread_join(t2, &retval), uintptr_t(0));
 107   ASSERT_EQ(uintptr_t(retval), 0);
 108
 109   ASSERT_EQ(done_count.val, 2U);
 110
 111   LIBC_NAMESPACE::pthread_mutex_destroy(&once_func_blocker);
 112 }
 113
 114 TEST_MAIN() {
 115   call_from_5_threads();
 116   test_synchronization();
 117   return 0;
 118 }