main.cpp revision 5cac6a54b36dd4f9b0db570720b8d47a487343f9 
1//===-- main.cpp ------------------------------------------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10// C includes
11#include <pthread.h>
12#include <stdio.h>
13#include <stdint.h>
14#include <stdlib.h>
15#include <unistd.h>
16
17pthread_t g_thread_1 = NULL;
18pthread_t g_thread_2 = NULL;
19pthread_t g_thread_3 = NULL;
20
21char *g_char_ptr = NULL;
22
23void
24do_bad_thing_with_location(char *char_ptr, char new_val)
25{
26    *char_ptr = new_val;
27}
28
29uint32_t access_pool (uint32_t flag = 0);
30
31uint32_t
32access_pool (uint32_t flag)
33{
34    static pthread_mutex_t g_access_mutex = PTHREAD_MUTEX_INITIALIZER;
35    if (flag == 0)
36        ::pthread_mutex_lock (&g_access_mutex);
37
38    char old_val = *g_char_ptr;
39    if (flag != 0)
40        do_bad_thing_with_location(g_char_ptr, old_val + 1);
41
42    if (flag == 0)
43        ::pthread_mutex_unlock (&g_access_mutex);
44    return *g_char_ptr;
45}
46
47void *
48thread_func (void *arg)
49{
50    uint32_t thread_index = *((uint32_t *)arg);
51    printf ("%s (thread index = %u) startng...\n", __FUNCTION__, thread_index);
52
53    uint32_t count = 0;
54    uint32_t val;
55    while (count++ < 15)
56    {
57        // random micro second sleep from zero to 3 seconds
58        int usec = ::rand() % 3000000;
59        printf ("%s (thread = %u) doing a usleep (%d)...\n", __FUNCTION__, thread_index, usec);
60        ::usleep (usec);
61
62        if (count < 7)
63            val = access_pool ();
64        else
65            val = access_pool (1);
66
67        printf ("%s (thread = %u) after usleep access_pool returns %d (count=%d)...\n", __FUNCTION__, thread_index, val, count);
68    }
69    printf ("%s (thread index = %u) exiting...\n", __FUNCTION__, thread_index);
70    return NULL;
71}
72
73
74int main (int argc, char const *argv[])
75{
76    int err;
77    void *thread_result = NULL;
78    uint32_t thread_index_1 = 1;
79    uint32_t thread_index_2 = 2;
80    uint32_t thread_index_3 = 3;
81
82    g_char_ptr = (char *)malloc (1);
83    *g_char_ptr = 0;
84
85    // Create 3 threads
86    err = ::pthread_create (&g_thread_1, NULL, thread_func, &thread_index_1);
87    err = ::pthread_create (&g_thread_2, NULL, thread_func, &thread_index_2);
88    err = ::pthread_create (&g_thread_3, NULL, thread_func, &thread_index_3);
89
90    printf ("Before turning all three threads loose...\n"); // Set break point at this line.
91
92    // Join all of our threads
93    err = ::pthread_join (g_thread_1, &thread_result);
94    err = ::pthread_join (g_thread_2, &thread_result);
95    err = ::pthread_join (g_thread_3, &thread_result);
96
97    return 0;
98}
99