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150
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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, &buf, 1);
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19 if (n != 1) {
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236
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20 // This read can "legitimately" fail regardless of the fact that glibc claims
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150
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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("/dev/urandom", O_RDONLY);
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44 int fd2 = open("/dev/urandom", O_RDONLY);
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45 if (fd == -1 || fd2 == -1)
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46 exit(printf("open failed\n"));
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47 pthread_t th;
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48 pthread_create(&th, 0, Thread, 0);
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49 if (dup2(fd2, fd) == -1)
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50 exit(printf("dup2 failed\n"));
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51 pthread_join(th, 0);
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52 if (close(fd) == -1)
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53 exit(printf("close failed\n"));
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54 if (close(fd2) == -1)
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55 exit(printf("close failed\n"));
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56 fprintf(stderr, "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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