Linux: inform the Zygote when it's waiting on a dead process

content/zygote/zygote_linux.cc

Index: content/zygote/zygote_linux.cc
diff --git a/content/zygote/zygote_linux.cc b/content/zygote/zygote_linux.cc
index a5fb2038050c621f518a635e07203453ecf69c06..2ae6784c6a87005d915b2c3685338dc9c623f975 100644
--- a/content/zygote/zygote_linux.cc
+++ b/content/zygote/zygote_linux.cc
@@ -204,9 +204,11 @@ void Zygote::HandleReapRequest(int fd,
 void Zygote::HandleGetTerminationStatus(int fd,
                                         const Pickle& pickle,
                                         PickleIterator iter) {
+  bool known_dead;
   base::ProcessHandle child;
 
-  if (!pickle.ReadInt(&iter, &child)) {
+  if (!pickle.ReadBool(&iter, &known_dead) ||
+      !pickle.ReadInt(&iter, &child)) {
     LOG(WARNING) << "Error parsing GetTerminationStatus request "
                  << "from browser";
     return;
@@ -217,7 +219,20 @@ void Zygote::HandleGetTerminationStatus(int fd,
   if (UsingSUIDSandbox())
     child = real_pids_to_sandbox_pids[child];
   if (child) {
-    status = base::GetTerminationStatus(child, &exit_code);
+    if (known_dead) {
+      // If we know that the process is already dead and the kernel is cleaning
+      // it up, we do want to wait until it becomes a zombie and not risk
+      // returning eroneously that it is still running. However, we do not
+      // want to risk a bug where we're told a process is dead when it's not.
+      // By sending SIGKILL, we make sure that WaitForTerminationStatus will
+      // return quickly even in this case.
+      if (kill(child, SIGKILL)) {
+        PLOG(ERROR) << "kill (" << child << ")";
+      }
+      status = base::WaitForTerminationStatus(child, &exit_code);
+    } else {
+      status = base::GetTerminationStatus(child, &exit_code);
+    }
   } else {
     // Assume that if we can't find the child in the sandbox, then
     // it terminated normally.