[compiler-rt] r240943 - tsan: fix flaky test
Dmitry Vyukov
dvyukov at google.com
Mon Jun 29 06:56:32 PDT 2015
Author: dvyukov
Date: Mon Jun 29 08:56:31 2015
New Revision: 240943
URL: http://llvm.org/viewvc/llvm-project?rev=240943&view=rev
Log:
tsan: fix flaky test
See the comment for explanation.
Modified:
compiler-rt/trunk/test/tsan/fd_dup_norace2.cc
Modified: compiler-rt/trunk/test/tsan/fd_dup_norace2.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/test/tsan/fd_dup_norace2.cc?rev=240943&r1=240942&r2=240943&view=diff
==============================================================================
--- compiler-rt/trunk/test/tsan/fd_dup_norace2.cc (original)
+++ compiler-rt/trunk/test/tsan/fd_dup_norace2.cc Mon Jun 29 08:56:31 2015
@@ -3,6 +3,7 @@
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
+#include <errno.h>
// dup2(oldfd, newfd) races with read(newfd).
// This is not reported as race because:
@@ -14,14 +15,33 @@ int fd;
void *Thread(void *x) {
char buf;
- if (read(fd, &buf, 1) != 1)
- exit(printf("read failed\n"));
+ int n = read(fd, &buf, 1);
+ if (n != 1) {
+ // This read can "legitimately" fail regadless of the fact that glibc claims
+ // that "there is no instant in the middle of calling dup2 at which new is
+ // closed and not yet a duplicate of old". Strace of the failing runs
+ // looks as follows:
+ //
+ // [pid 122196] open("/dev/urandom", O_RDONLY) = 3
+ // [pid 122196] open("/dev/urandom", O_RDONLY) = 4
+ // Process 122382 attached
+ // [pid 122382] read(3, <unfinished ...>
+ // [pid 122196] dup2(4, 3 <unfinished ...>
+ // [pid 122382] <... read resumed> 0x7fcd139960b7, 1) = -1 EBADF (Bad file descriptor)
+ // [pid 122196] <... dup2 resumed> ) = 3
+ // read failed: n=-1 errno=9
+ //
+ // The failing read does not interfere with what this test tests,
+ // so we just ignore the failure.
+ //
+ // exit(printf("read failed: n=%d errno=%d\n", n, errno));
+ }
return 0;
}
int main() {
- fd = open("/dev/random", O_RDONLY);
- int fd2 = open("/dev/random", O_RDONLY);
+ fd = open("/dev/urandom", O_RDONLY);
+ int fd2 = open("/dev/urandom", O_RDONLY);
if (fd == -1 || fd2 == -1)
exit(printf("open failed\n"));
pthread_t th;
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