1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
| // RUN: %clangxx_tsan -O1 %s %link_libcxx_tsan -o %t && %run %t 2>&1 | FileCheck %s
#include <pthread.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <time.h>
#include <errno.h>
#include <vector>
#include <algorithm>
#include <sys/time.h>
const int kThreads = 4;
const int kMutexes = 16 << 10;
const int kIters = 400 << 10;
const int kMaxPerThread = 10;
const int kStateInited = 0;
const int kStateNotInited = -1;
const int kStateLocked = -2;
struct Mutex {
int state;
pthread_rwlock_t m;
};
Mutex mtx[kMutexes];
void check(int res) {
if (res != 0) {
printf("SOMETHING HAS FAILED\n");
exit(1);
}
}
bool cas(int *a, int oldval, int newval) {
return __atomic_compare_exchange_n(a, &oldval, newval, false,
__ATOMIC_ACQ_REL, __ATOMIC_RELAXED);
}
void *Thread(void *seed) {
unsigned rnd = (unsigned)(unsigned long)seed;
int err;
std::vector<int> locked;
for (int i = 0; i < kIters; i++) {
int what = rand_r(&rnd) % 10;
if (what < 4 && locked.size() < kMaxPerThread) {
// lock
int max_locked = -1;
if (!locked.empty()) {
max_locked = *std::max_element(locked.begin(), locked.end());
if (max_locked == kMutexes - 1) {
i--;
continue;
}
}
int id = (rand_r(&rnd) % (kMutexes - max_locked - 1)) + max_locked + 1;
Mutex *m = &mtx[id];
// init the mutex if necessary or acquire a reference
for (;;) {
int old = __atomic_load_n(&m->state, __ATOMIC_RELAXED);
if (old == kStateLocked) {
sched_yield();
continue;
}
int newv = old + 1;
if (old == kStateNotInited)
newv = kStateLocked;
if (cas(&m->state, old, newv)) {
if (old == kStateNotInited) {
if ((err = pthread_rwlock_init(&m->m, 0))) {
fprintf(stderr, "pthread_rwlock_init failed with %d\n", err);
exit(1);
}
if (!cas(&m->state, kStateLocked, 1)) {
fprintf(stderr, "init commit failed\n");
exit(1);
}
}
break;
}
}
// now we have an inited and referenced mutex, choose what to do
bool failed = false;
switch (rand_r(&rnd) % 4) {
case 0:
if ((err = pthread_rwlock_wrlock(&m->m))) {
fprintf(stderr, "pthread_rwlock_wrlock failed with %d\n", err);
exit(1);
}
break;
case 1:
if ((err = pthread_rwlock_rdlock(&m->m))) {
fprintf(stderr, "pthread_rwlock_rdlock failed with %d\n", err);
exit(1);
}
break;
case 2:
err = pthread_rwlock_trywrlock(&m->m);
if (err != 0 && err != EBUSY) {
fprintf(stderr, "pthread_rwlock_trywrlock failed with %d\n", err);
exit(1);
}
failed = err == EBUSY;
break;
case 3:
err = pthread_rwlock_tryrdlock(&m->m);
if (err != 0 && err != EBUSY) {
fprintf(stderr, "pthread_rwlock_tryrdlock failed with %d\n", err);
exit(1);
}
failed = err == EBUSY;
break;
}
if (failed) {
if (__atomic_fetch_sub(&m->state, 1, __ATOMIC_ACQ_REL) <= 0) {
fprintf(stderr, "failed to unref after failed trylock\n");
exit(1);
}
continue;
}
locked.push_back(id);
} else if (what < 9 && !locked.empty()) {
// unlock
int pos = rand_r(&rnd) % locked.size();
int id = locked[pos];
locked[pos] = locked[locked.size() - 1];
locked.pop_back();
Mutex *m = &mtx[id];
if ((err = pthread_rwlock_unlock(&m->m))) {
fprintf(stderr, "pthread_rwlock_unlock failed with %d\n", err);
exit(1);
}
if (__atomic_fetch_sub(&m->state, 1, __ATOMIC_ACQ_REL) <= 0) {
fprintf(stderr, "failed to unref after unlock\n");
exit(1);
}
} else {
// Destroy a random mutex.
int id = rand_r(&rnd) % kMutexes;
Mutex *m = &mtx[id];
if (!cas(&m->state, kStateInited, kStateLocked)) {
i--;
continue;
}
if ((err = pthread_rwlock_destroy(&m->m))) {
fprintf(stderr, "pthread_rwlock_destroy failed with %d\n", err);
exit(1);
}
if (!cas(&m->state, kStateLocked, kStateNotInited)) {
fprintf(stderr, "destroy commit failed\n");
exit(1);
}
}
}
// Unlock all previously locked mutexes, otherwise other threads can deadlock.
for (int i = 0; i < locked.size(); i++) {
int id = locked[i];
Mutex *m = &mtx[id];
if ((err = pthread_rwlock_unlock(&m->m))) {
fprintf(stderr, "pthread_rwlock_unlock failed with %d\n", err);
exit(1);
}
}
return 0;
}
int main() {
struct timeval tv;
gettimeofday(&tv, NULL);
unsigned s = tv.tv_sec + tv.tv_usec;
fprintf(stderr, "seed %d\n", s);
srand(s);
for (int i = 0; i < kMutexes; i++)
mtx[i].state = kStateNotInited;
pthread_t t[kThreads];
for (int i = 0; i < kThreads; i++)
pthread_create(&t[i], 0, Thread, (void*)(unsigned long)rand());
for (int i = 0; i < kThreads; i++)
pthread_join(t[i], 0);
fprintf(stderr, "DONE\n");
return 0;
}
// CHECK-NOT: WARNING: ThreadSanitizer
// CHECK: DONE
|