1// RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
2#include "test.h"
3#include <sys/types.h>
4#include <sys/stat.h>
5#include <fcntl.h>
6#include <errno.h>
7
8// dup2(oldfd, newfd) races with read(newfd).
9// This is not reported as race because:
10// 1. Some software dups a closed pipe in place of a socket before closing
11//    the socket (to prevent races actually).
12// 2. Some daemons dup /dev/null in place of stdin/stdout.
13
14int fd;
15
16void *Thread(void *x) {
17  char buf;
18  int n = read(fd, &buf, 1);
19  if (n != 1) {
20    // This read can "legitimately" fail regadless of the fact that glibc claims
21    // that "there is no instant in the middle of calling dup2 at which new is
22    // closed and not yet a duplicate of old". Strace of the failing runs
23    // looks as follows:
24    //
25    //    [pid 122196] open("/dev/urandom", O_RDONLY) = 3
26    //    [pid 122196] open("/dev/urandom", O_RDONLY) = 4
27    //    Process 122382 attached
28    //    [pid 122382] read(3,  <unfinished ...>
29    //    [pid 122196] dup2(4, 3 <unfinished ...>
30    //    [pid 122382] <... read resumed> 0x7fcd139960b7, 1) = -1 EBADF (Bad file descriptor)
31    //    [pid 122196] <... dup2 resumed> )       = 3
32    //    read failed: n=-1 errno=9
33    //
34    // The failing read does not interfere with what this test tests,
35    // so we just ignore the failure.
36    //
37    // exit(printf("read failed: n=%d errno=%d\n", n, errno));
38  }
39  return 0;
40}
41
42int main() {
43  fd = open("/dev/urandom", O_RDONLY);
44  int fd2 = open("/dev/urandom", O_RDONLY);
45  if (fd == -1 || fd2 == -1)
46    exit(printf("open failed\n"));
47  pthread_t th;
48  pthread_create(&th, 0, Thread, 0);
49  if (dup2(fd2, fd) == -1)
50    exit(printf("dup2 failed\n"));
51  pthread_join(th, 0);
52  if (close(fd) == -1)
53    exit(printf("close failed\n"));
54  if (close(fd2) == -1)
55    exit(printf("close failed\n"));
56  fprintf(stderr, "DONE\n");
57}
58
59// CHECK-NOT: WARNING: ThreadSanitizer: data race
60// CHECK: DONE
61