Bug 1633791 part 1: Add ability to notify the child processes of an impending shutdown. r=nika

This also adds a call to the new function in ContentParent::StartForceKillTimer.

Differential Revision: https://phabricator.services.mozilla.com/D75507

dom/ipc/ContentParent.cpp

@@ -1856,6 +1856,8 @@ void ContentParent::StartForceKillTimer() {
     return;
   }
 
+  NotifyImpendingShutdown();
+
   int32_t timeoutSecs = StaticPrefs::dom_ipc_tabs_shutdownTimeoutSecs();
   if (timeoutSecs > 0) {
     NS_NewTimerWithFuncCallback(getter_AddRefs(mForceKillTimer),

ipc/glue/MessageChannel.cpp

@@ -1150,6 +1150,10 @@ bool MessageChannel::MaybeInterceptSpecialIOMessage(const Message& aMsg) {
       IPC_LOG("Build IDs match message");
       mBuildIDsConfirmedMatch = true;
       return true;
+    } else if (IMPENDING_SHUTDOWN_MESSAGE_TYPE == aMsg.type()) {
+      IPC_LOG("Impending Shutdown received");
+      ProcessChild::NotifyImpendingShutdown();
+      return true;
     }
   }
   return false;
@@ -2688,6 +2692,17 @@ void MessageChannel::CloseWithTimeout() {
   mChannelState = ChannelTimeout;
 }
 
+void MessageChannel::NotifyImpendingShutdown() {
+  UniquePtr<Message> msg =
+      MakeUnique<Message>(MSG_ROUTING_NONE, IMPENDING_SHUTDOWN_MESSAGE_TYPE);
+  MonitorAutoLock lock(*mMonitor);
+  if (Connected()) {
+    MOZ_DIAGNOSTIC_ASSERT(mIsCrossProcess);
+    // SendMessage takes ownership of the message.
+    mLink->SendMessage(msg.release());
+  }
+}
+
 void MessageChannel::Close() {
   AssertWorkerThread();
 

ipc/glue/MessageChannel.h

@@ -177,6 +177,12 @@ class MessageChannel : HasResultCodes, MessageLoop::DestructionObserver {
   // sends, to avoid deadlocks.
   bool OpenOnSameThread(MessageChannel* aTargetChan, Side aSide);
 
+  /**
+   * This sends a special message that is processed on the IO thread, so that
+   * other actors can know that the process will soon shutdown.
+   */
+  void NotifyImpendingShutdown();
+
   // Close the underlying transport channel.
   void Close();
 

ipc/glue/ProcessChild.cpp

@@ -4,6 +4,8 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+#include "mozilla/ipc/ProcessChild.h"
+
 #include "nsDebug.h"
 
 #ifdef XP_WIN
@@ -14,13 +16,14 @@
 
 #include "mozilla/AppShutdown.h"
 #include "mozilla/ipc/IOThreadChild.h"
-#include "mozilla/ipc/ProcessChild.h"
 
 namespace mozilla {
 namespace ipc {
 
 ProcessChild* ProcessChild::gProcessChild;
 
+static Atomic<bool> sExpectingShutdown(false);
+
 ProcessChild::ProcessChild(ProcessId aParentPid)
     : ChildProcess(new IOThreadChild()),
       mUILoop(MessageLoop::current()),
@@ -32,6 +35,12 @@ ProcessChild::ProcessChild(ProcessId aParentPid)
 
 ProcessChild::~ProcessChild() { gProcessChild = nullptr; }
 
+/* static */
+void ProcessChild::NotifyImpendingShutdown() { sExpectingShutdown = true; }
+
+/* static */
+bool ProcessChild::ExpectingShutdown() { return sExpectingShutdown; }
+
 /* static */
 void ProcessChild::QuickExit() { AppShutdown::DoImmediateExit(); }
 

ipc/glue/ProcessChild.h

@@ -32,6 +32,10 @@ class ProcessChild : public ChildProcess {
 
   static MessageLoop* message_loop() { return gProcessChild->mUILoop; }
 
+  static void NotifyImpendingShutdown();
+
+  static bool ExpectingShutdown();
+
   /**
    * Exit *now*.  Do not shut down XPCOM, do not pass Go, do not run
    * static destructors, do not collect $200.

ipc/glue/ProtocolUtils.cpp

@@ -614,6 +614,10 @@ bool IToplevelProtocol::OpenOnSameThread(MessageChannel* aChannel, Side aSide) {
   return GetIPCChannel()->OpenOnSameThread(aChannel, aSide);
 }
 
+void IToplevelProtocol::NotifyImpendingShutdown() {
+  GetIPCChannel()->NotifyImpendingShutdown();
+}
+
 void IToplevelProtocol::Close() { GetIPCChannel()->Close(); }
 
 void IToplevelProtocol::SetReplyTimeoutMs(int32_t aTimeoutMs) {

ipc/glue/ProtocolUtils.h

@@ -52,6 +52,7 @@ namespace {
 // protocol 0.  Oops!  We can get away with this until protocol 0
 // starts approaching its 65,536th message.
 enum {
+  IMPENDING_SHUTDOWN_MESSAGE_TYPE = kuint16max - 9,
   BUILD_IDS_MATCH_MESSAGE_TYPE = kuint16max - 8,
   BUILD_ID_MESSAGE_TYPE = kuint16max - 7,  // unused
   CHANNEL_OPENED_MESSAGE_TYPE = kuint16max - 6,
@@ -444,6 +445,12 @@ class IToplevelProtocol : public IProtocol {
   bool OpenOnSameThread(MessageChannel* aChannel,
                         mozilla::ipc::Side aSide = mozilla::ipc::UnknownSide);
 
+  /**
+   * This sends a special message that is processed on the IO thread, so that
+   * other actors can know that the process will soon shutdown.
+   */
+  void NotifyImpendingShutdown();
+
   void Close();
 
   void SetReplyTimeoutMs(int32_t aTimeoutMs);