Bug 1609881 - Part 1: put the fork server behind a preference. r=gsvelto

Differential Revision: https://phabricator.services.mozilla.com/D61141

--HG--
extra : moz-landing-system : lando

ipc/chromium/src/base/process_util_linux.cc

@@ -215,7 +215,7 @@ static bool LaunchAppWithForkServer(const std::vector<std::string>& argv,
 bool LaunchApp(const std::vector<std::string>& argv,
                const LaunchOptions& options, ProcessHandle* process_handle) {
 #if defined(MOZ_ENABLE_FORKSERVER)
-  if (options.use_forkserver) {
+  if (options.use_forkserver && ForkServiceChild::Get()) {
     return LaunchAppWithForkServer(argv, options, process_handle);
   }
 #endif

ipc/glue/ForkServiceChild.cpp

@@ -1,5 +1,5 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/* vim: set ts=8 sts=4 et sw=4 tw=80: */
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * 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/. */
@@ -8,6 +8,7 @@
 #include "mozilla/ipc/IPDLParamTraits.h"
 #include "mozilla/Logging.h"
 #include "mozilla/ipc/GeckoChildProcessHost.h"
+#include "mozilla/StaticPrefs_dom.h"
 
 #include <unistd.h>
 #include <fcntl.h>
@@ -124,7 +125,9 @@ already_AddRefed<ForkServerLauncher> ForkServerLauncher::Create() {
 NS_IMETHODIMP
 ForkServerLauncher::Observe(nsISupports* aSubject, const char* aTopic,
                             const char16_t* aData) {
-  if (!mHaveStartedClient && strcmp(aTopic, NS_XPCOM_STARTUP_CATEGORY) == 0) {
+  if (!mHaveStartedClient &&
+      strcmp(aTopic, NS_XPCOM_STARTUP_CATEGORY) == 0 &&
+      StaticPrefs::dom_ipc_forkserver_enable_AtStartup()) {
     mHaveStartedClient = true;
     ForkServiceChild::StartForkServer();
 

ipc/glue/ForkServiceChild.h

@@ -1,5 +1,5 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/* vim: set ts=8 sts=4 et sw=4 tw=80: */
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * 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/. */

ipc/glue/GeckoChildProcessHost.cpp

@@ -362,7 +362,8 @@ GeckoChildProcessHost::GeckoChildProcessHost(GeckoProcessType aProcessType,
   }
 #endif
 #if defined(MOZ_ENABLE_FORKSERVER)
-  if (aProcessType == GeckoProcessType_Content) {
+  if (aProcessType == GeckoProcessType_Content &&
+      ForkServiceChild::Get()) {
     mLaunchOptions->use_forkserver = true;
   }
 #endif

modules/libpref/init/StaticPrefList.yaml

@@ -1676,6 +1676,13 @@
   value: 500
   mirror: always
 
+#ifdef MOZ_ENABLE_FORKSERVER
+- name: dom.ipc.forkserver.enable
+  type: bool
+  value: false
+  mirror: once
+#endif
+
 # Whether or not to collect a paired minidump when force-killing a
 # content process.
 - name: dom.ipc.tabs.createKillHardCrashReports