1 // RUN: %clang_tsan %s -lstdc++ -o %t && %run %t 2>&1 | FileCheck %s
2
3 #include "../test.h"
4 #include <errno.h>
5 #include <linux/futex.h>
6 #include <pthread.h>
7 #include <signal.h>
8 #include <stdio.h>
9 #include <sys/syscall.h>
10
11 #include <cassert>
12 #include <stdexcept>
13 #include <thread>
14
15 #include <sanitizer/linux_syscall_hooks.h>
16
futex(int * uaddr,int futex_op,int val,const struct timespec * timeout,int * uaddr2,int val3)17 int futex(int *uaddr, int futex_op, int val, const struct timespec *timeout,
18 int *uaddr2, int val3) {
19 __sanitizer_syscall_pre_futex(uaddr, futex_op, val, timeout, uaddr2, val3);
20 int result = syscall(SYS_futex, uaddr, futex_op, val, timeout, uaddr2, val3);
21 __sanitizer_syscall_post_futex(result, uaddr, futex_op, val, timeout, uaddr2,
22 val3);
23 return result;
24 }
25
26 // Simple mutex implementation using futex.
27 class Mutex {
28 public:
Mutex()29 Mutex() : value(0) {}
30
lock()31 void lock() {
32 int c;
33 while ((c = __sync_val_compare_and_swap(&value, 0, 1)) != 0) {
34 if (c != 1)
35 continue;
36 int r = futex(&value, FUTEX_WAIT_PRIVATE, 1, nullptr, nullptr, 0);
37 if (r == -1 && errno != EAGAIN) {
38 fprintf(stderr, "futex wait error\n");
39 abort();
40 }
41 }
42 }
43
unlock()44 void unlock() {
45 value = 0;
46 int r = futex(&value, FUTEX_WAKE_PRIVATE, 1, nullptr, nullptr, 0);
47 if (r == -1) {
48 fprintf(stderr, "futex wake error\n");
49 abort();
50 }
51 }
52
53 private:
54 int value;
55 };
56
57 Mutex mutex;
58
Thread(void * x)59 void *Thread(void *x) {
60 // Waiting for the futex.
61 mutex.lock();
62 // Finished waiting.
63 return nullptr;
64 }
65
SigprofHandler(int signal,siginfo_t * info,void * context)66 static void SigprofHandler(int signal, siginfo_t *info, void *context) {
67 // Unlock the futex.
68 mutex.unlock();
69 }
70
InstallSignalHandler()71 void InstallSignalHandler() {
72 struct sigaction sa;
73 sa.sa_sigaction = SigprofHandler;
74 sigemptyset(&sa.sa_mask);
75 sa.sa_flags = SA_RESTART | SA_SIGINFO;
76 if (sigaction(SIGPROF, &sa, 0) != 0) {
77 fprintf(stderr, "failed to install signal handler\n");
78 abort();
79 }
80 }
81
main()82 int main() {
83 alarm(60); // Kill the test if it hangs.
84
85 // Install the signal handler
86 InstallSignalHandler();
87
88 // Lock the futex at first so the other thread will wait for it.
89 mutex.lock();
90
91 // Create the thread to wait for the futex.
92 pthread_t thread;
93 pthread_create(&thread, NULL, Thread, NULL);
94
95 // Just waiting a bit to make sure the thead is at the FUTEX_WAIT_PRIVATE
96 // syscall.
97 std::this_thread::sleep_for(std::chrono::milliseconds(100));
98
99 // Send the signal to the other thread, which will send the futex wake
100 // syscall.
101 int r = pthread_kill(thread, SIGPROF);
102 assert(r == 0);
103
104 // Futex should be notified and the thread should be able to continue.
105 pthread_join(thread, NULL);
106
107 // Exiting successfully.
108 fprintf(stderr, "PASS\n");
109 return 0;
110 }
111
112 // CHECK-NOT: WARNING: ThreadSanitizer:
113 // CHECK: PASS
114