Linux: tear down Zygote at browser shutdown.

content/browser/zygote_host/zygote_host_impl_linux.cc

Index: content/browser/zygote_host/zygote_host_impl_linux.cc
diff --git a/content/browser/zygote_host/zygote_host_impl_linux.cc b/content/browser/zygote_host/zygote_host_impl_linux.cc
index 044dedc9efa578aaf4a8249f0d914b99c5085bda..daae1068cf1ace9e665f6d5e04f0117e8dd34d90 100644
--- a/content/browser/zygote_host/zygote_host_impl_linux.cc
+++ b/content/browser/zygote_host/zygote_host_impl_linux.cc
@@ -59,8 +59,7 @@ ZygoteHostImpl::ZygoteHostImpl()
       sandbox_status_(0) {}
 
 ZygoteHostImpl::~ZygoteHostImpl() {
-  if (init_)
-    close(control_fd_);
+  TearDown();
 }
 
 // static
@@ -217,6 +216,18 @@ void ZygoteHostImpl::Init(const std::string& sandbox_cmd) {
   // We don't wait for the reply. We'll read it in ReadReply.
 }
 
+void ZygoteHostImpl::TearDown() {
+  if (init_) {
+    // Closing the IPC channel will act as a notification to exit
+    // to the Zygote.
+    if (IGNORE_EINTR(close(control_fd_))) {
+      PLOG(ERROR) << "Could not close Zygote control channel.";
+      NOTREACHED();
+    }

[piman, 2014/01/28 02:20:44]

nit: maybe reset control_fd_ to -1 for added defense against races / bad usage.

Speaking of races, this is called on the main (UI) thread, before the IO thread
is torn down. I think most of the other methods are called from the IO thread.
Isn't there a race risk? Should this be done under control_lock_? And have
SendMessage/ReadReply properly check the value of control_fd and/or init_ and
return failure?

[jln (very slow on Chromium), 2014/01/28 02:52:45]

Done. I hadn't done it because "init_" is checked in almost all places anyways.
That race existed before (in the destructor), but you're right that this could
make it worse.

That a lock could be problematic for fringe cases (for instance if Zygote is
SIGSTOP-ed), but otherwise we should be fine. Added!

+    init_ = false;
+  }
+}
+
 bool ZygoteHostImpl::SendMessage(const Pickle& data,
                                  const std::vector<int>* fds) {
   CHECK(data.size() <= kZygoteMaxMessageLength)