From bbe84149083db23ba356b15d820d29e7798bfe5a Mon Sep 17 00:00:00 2001
From: Anna Henningsen <anna@addaleax.net>
Date: Sun, 3 Feb 2019 20:20:52 +0100
Subject: [PATCH] worker: add mutex lock to MessagePort ctor
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Automated tooling for race condition detection reports this as a
possible problem. It’s unlikely that something bad would happen
here (beyond maybe calling `TriggerAsync()` twice), but adding this
should be okay.
---
 src/node_messaging.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/node_messaging.cc b/src/node_messaging.cc
index 6e8e3e8ad76e03..9952043f7b4c34 100644
--- a/src/node_messaging.cc
+++ b/src/node_messaging.cc
@@ -533,6 +533,11 @@ MessagePort* MessagePort::New(
   if (data) {
     port->Detach();
     port->data_ = std::move(data);
+
+    // This lock is here to avoid race conditions with the `owner_` read
+    // in AddToIncomingQueue(). (This would likely be unproblematic without it,
+    // but it's better to be safe than sorry.)
+    Mutex::ScopedLock lock(port->data_->mutex_);
     port->data_->owner_ = port;
     // If the existing MessagePortData object had pending messages, this is
     // the easiest way to run that queue.