tsan: support setuid call

Currently the call hangs because the background thread
does not handle SIGSETXID signal.

llvm-svn: 235581

compiler-rt/lib/sanitizer_common/sanitizer_linux.cc

@@ -915,6 +915,9 @@ void *internal_start_thread(void(*func)(void *arg), void *arg) {
   // Start the thread with signals blocked, otherwise it can steal user signals.
   __sanitizer_sigset_t set, old;
   internal_sigfillset(&set);
+  // Glibc uses SIGSETXID signal during setuid call. If this signal is blocked
+  // on any thread, setuid call hangs (see test/tsan/setuid.c).
+  internal_sigdelset(&set, 33);
   internal_sigprocmask(SIG_SETMASK, &set, &old);
   void *th;
   real_pthread_create(&th, 0, (void*(*)(void *arg))func, arg);

compiler-rt/test/tsan/setuid.c

@@ -0,0 +1,26 @@
+// RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
+#include "test.h"
+#include <sys/types.h>
+#include <unistd.h>
+
+// Setuid call used to hang because the background tsan thread did not handle
+// SIGSETXID signal. Note that we don't care whether setuid call succeeds
+// or not.
+
+static void *thread(void *arg) {
+  (void)arg;
+  sleep(1);
+  return 0;
+}
+
+int main() {
+  // Create another thread just for completeness of the picture.
+  pthread_t th;
+  pthread_create(&th, 0, thread, 0);
+  setuid(0);
+  pthread_join(th, 0);
+  fprintf(stderr, "DONE\n");
+  return 0;
+}
+
+// CHECK: DONE