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
17 pthread_t g_thread_1 = NULL;
18 pthread_t g_thread_2 = NULL;
19 pthread_t g_thread_3 = NULL;
20
21 char *g_char_ptr = NULL;
22
23 void
do_bad_thing_with_location(char * char_ptr,char new_val)24 do_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
31 uint32_t access_pool (uint32_t flag = 0);
32
33 uint32_t
access_pool(uint32_t flag)34 access_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
49 void *
thread_func(void * arg)50 thread_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
main(int argc,char const * argv[])76 int 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