1 /** Cause a race inside code protected by a reader lock.
2 */
3
4
5 /* Needed for older glibc's (2.3 and older, at least) who don't
6 otherwise "know" about pthread_rwlock_anything or about
7 PTHREAD_MUTEX_RECURSIVE (amongst things). */
8
9 #define _GNU_SOURCE 1
10
11 #include <pthread.h>
12 #include <stdio.h>
13 #include <unistd.h>
14
15
16
17 static pthread_rwlock_t s_rwlock;
18 static int s_racy;
19
sleep_ms(const int ms)20 static void sleep_ms(const int ms)
21 {
22 struct timespec delay = { ms / 1000, (ms % 1000) * 1000 * 1000 };
23 nanosleep(&delay, 0);
24 }
25
thread_func(void * arg)26 static void* thread_func(void* arg)
27 {
28 pthread_rwlock_rdlock(&s_rwlock);
29 s_racy++;
30 pthread_rwlock_unlock(&s_rwlock);
31 sleep_ms(100);
32 return 0;
33 }
34
main(int argc,char ** argv)35 int main(int argc, char** argv)
36 {
37 pthread_t thread1;
38 pthread_t thread2;
39
40 #if 0
41
42 VALGRIND_DO_CLIENT_REQUEST_STMT(VG_USERREQ__DRD_TRACE_ADDR,
43 &s_racy, 0, 0, 0, 0);
44 #endif
45
46 pthread_rwlock_init(&s_rwlock, 0);
47 pthread_create(&thread1, 0, thread_func, 0);
48 pthread_create(&thread2, 0, thread_func, 0);
49 pthread_join(thread1, 0);
50 pthread_join(thread2, 0);
51 pthread_rwlock_destroy(&s_rwlock);
52
53 fprintf(stderr, "Result: %d\n", s_racy);
54
55 return 0;
56 }
57