tsan: improve error message in test

we've seen a flake on this test
next time it happens we will be able to gather some info

llvm-svn: 205619

diff --git a/compiler-rt/test/tsan/race_on_read.cc b/compiler-rt/test/tsan/race_on_read.cc
index e870ff9e83c6bd4dad54c29362bd7199e052abbd..bae3e5ba994f1754cc165c02528c18ab0f2bd9cf 100644 (file)
--- a/compiler-rt/test/tsan/race_on_read.cc
+++ b/compiler-rt/test/tsan/race_on_read.cc
@@ -6,6 +6,7 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <errno.h>
 
 int fd;
 char buf;
@@ -18,13 +19,17 @@ void *Thread(void *x) {
 
 int main() {
   fd = open("/dev/random", O_RDONLY);
-  if (fd < 0) return 1;
+  if (fd < 0) {
+    fprintf(stderr, "failed to open /dev/random (%d)\n", errno);
+    return 1;
+  }
   pthread_t t[2];
   pthread_create(&t[0], NULL, Thread, NULL);
   pthread_create(&t[1], NULL, Thread, NULL);
   pthread_join(t[0], NULL);
   pthread_join(t[1], NULL);
   close(fd);
+  fprintf(stderr, "DONE\n");
 }
 
 // CHECK: WARNING: ThreadSanitizer: data race
@@ -32,3 +37,5 @@ int main() {
 // CHECK:     #0 read
 // CHECK:   Previous write of size 1
 // CHECK:     #0 read
+// CHECK: DONE
+