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92a42be0 SL |
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 | ||
14 | int fd; | |
15 | ||
16 | void *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 | ||
42 | int 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")); | |
5bcae85e | 56 | fprintf(stderr, "DONE\n"); |
92a42be0 SL |
57 | } |
58 | ||
59 | // CHECK-NOT: WARNING: ThreadSanitizer: data race | |
60 | // CHECK: DONE |