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    unsigned what = new_val;
27    printf("new value written to location(%p) = %u\n", char_ptr, what);
28    *char_ptr = new_val;
29}
30
31uint32_t access_pool (uint32_t flag = 0);
32
33uint32_t
34access_pool (uint32_t flag)
35{
36    static pthread_mutex_t g_access_mutex = PTHREAD_MUTEX_INITIALIZER;
37    if (flag == 0)
38        ::pthread_mutex_lock (&g_access_mutex);
39
40    char old_val = *g_char_ptr;
41    if (flag != 0)
42        do_bad_thing_with_location(g_char_ptr, old_val + 1);
43
44    if (flag == 0)
45        ::pthread_mutex_unlock (&g_access_mutex);
46    return *g_char_ptr;
47}
48
49void *
50thread_func (void *arg)
51{
52    uint32_t thread_index = *((uint32_t *)arg);
53    printf ("%s (thread index = %u) startng...\n", __FUNCTION__, thread_index);
54
55    uint32_t count = 0;
56    uint32_t val;
57    while (count++ < 15)
58    {
59        // random micro second sleep from zero to 3 seconds
60        int usec = ::rand() % 3000000;
61        printf ("%s (thread = %u) doing a usleep (%d)...\n", __FUNCTION__, thread_index, usec);
62        ::usleep (usec);
63
64        if (count < 7)
65            val = access_pool ();
66        else
67            val = access_pool (1);
68
69        printf ("%s (thread = %u) after usleep access_pool returns %d (count=%d)...\n", __FUNCTION__, thread_index, val, count);
70    }
71    printf ("%s (thread index = %u) exiting...\n", __FUNCTION__, thread_index);
72    return NULL;
73}
74
75
76int main (int argc, char const *argv[])
77{
78    int err;
79    void *thread_result = NULL;
80    uint32_t thread_index_1 = 1;
81    uint32_t thread_index_2 = 2;
82    uint32_t thread_index_3 = 3;
83
84    g_char_ptr = (char *)malloc (1);
85    *g_char_ptr = 0;
86
87    // Create 3 threads
88    err = ::pthread_create (&g_thread_1, NULL, thread_func, &thread_index_1);
89    err = ::pthread_create (&g_thread_2, NULL, thread_func, &thread_index_2);
90    err = ::pthread_create (&g_thread_3, NULL, thread_func, &thread_index_3);
91
92    printf ("Before turning all three threads loose...\n"); // Set break point at this line.
93
94    // Join all of our threads
95    err = ::pthread_join (g_thread_1, &thread_result);
96    err = ::pthread_join (g_thread_2, &thread_result);
97    err = ::pthread_join (g_thread_3, &thread_result);
98
99    return 0;
100}
101