From 17d0a01b8f4c294accba9faac3c1bdbf02166630 Mon Sep 17 00:00:00 2001
From: Roger Wang <roger@nwjs.io>
Date: Thu, 22 Oct 2020 08:03:12 -0600
Subject: [PATCH] Fix race condition in renderer message loop

Ref nwjs/nw.js#7497
Ref nwjs/nw.js#7590
---
 base/message_loop/message_pump_uv.cc | 9 +++++++++
 base/message_loop/message_pump_uv.h  | 2 ++
 2 files changed, 11 insertions(+)

diff --git a/base/message_loop/message_pump_uv.cc b/base/message_loop/message_pump_uv.cc
index 708fa0e17b50a..864bfebc41eb8 100644
--- a/base/message_loop/message_pump_uv.cc
+++ b/base/message_loop/message_pump_uv.cc
@@ -111,6 +111,13 @@ void MessagePumpUV::Run(Delegate* delegate) {
       continue;
     }
 
+    if (event_.IsSignaled()) {
+      //there is a chance that wake_event_ got processed in uv loop
+      //run above. then the next wait is stalled.
+      event_.Reset();
+      g_msg_pump_did_work_fn(&ctx);
+      continue;
+    }
     if (next_work_info.delayed_run_time.is_max()) {
       // (*node::g_nw_uv_run)(loop, UV_RUN_ONCE);
       g_msg_pump_need_work_fn(&ctx);
@@ -123,6 +130,7 @@ void MessagePumpUV::Run(Delegate* delegate) {
         // uv_timer_stop(&delay_timer);
       g_msg_pump_delay_work_fn(&ctx, delay.InMilliseconds());
     }
+    event_.Reset();
     // Since event_ is auto-reset, we don't need to do anything special here
     // other than service each delegate method.
   }
@@ -161,6 +169,7 @@ void MessagePumpUV::ScheduleWork() {
 // #else
 //   uv_async_send(wakeup_event_);
 // #endif
+  event_.Signal();
   g_msg_pump_sched_work_fn(wakeup_event_);
 }
 
diff --git a/base/message_loop/message_pump_uv.h b/base/message_loop/message_pump_uv.h
index a464e2a9963b7..5e7ddd920167f 100644
--- a/base/message_loop/message_pump_uv.h
+++ b/base/message_loop/message_pump_uv.h
@@ -9,6 +9,7 @@
 #include "base/message_loop/message_pump.h"
 #include "base/time/time.h"
 #include "content/common/content_export.h"
+#include "base/synchronization/waitable_event.h"
 
 #include <vector>
 
@@ -39,6 +40,7 @@ class BASE_EXPORT MessagePumpUV : public MessagePump {
   // Handle to wake up loop.
   std::vector<void*> wakeup_events_;
   void* wakeup_event_;
+  WaitableEvent event_;
 
   TimeTicks delayed_work_time_;