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