[sanitizer] Fix deadlock in StopTheWorld.

The tracer thread in StopTheWorld could wait on a mutex forever if the parent
process died before unlocking it. Use PR_SET_PDEATHSIG so that the parent would
kill the child in this scenario.

llvm-svn: 192210

1 files changed, 5 insertions, 0 deletions

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc b/compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
index 3c650be5c57..d63205345cc 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
@@ -224,6 +224,11 @@ static int TracerThread(void* argument) {
   TracerThreadArgument *tracer_thread_argument =
       (TracerThreadArgument *)argument;
 
+  internal_prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
+  // Check if parent is already dead.
+  if (internal_getppid() == 1)
+    internal__exit(4);
+
   // Wait for the parent thread to finish preparations.
   tracer_thread_argument->mutex.Lock();
   tracer_thread_argument->mutex.Unlock();