Revert 193486 "[Mac] Remove base::LaunchSynchronize and rewrite ..."

> [Mac] Remove base::LaunchSynchronize and rewrite content::MachBroker.
> 
> This restructures the way MachBroker parent-child communication happens. Now,
> the MachBroker lock will be held for the duration of LaunchProcess until the
> PID is returned and inserted into the MachMap. Since the lock must also be
> acquired on the broker thread to insert the received task port into the
> MachMap, this ensures that the placeholder is always inserted before the task
> port.
> 
> MachBroker has also been rewritten to use Mach IPC directly, rather than the C++
> wrappers in base/mach_ipc_mac.h. The wrappers are not flexible enough to allow
> the use of an audit trailer. This trailer is used to verify the PID of the
> sender of the check in message in the parent. Previously, this was done by
> another kernel trap, pid_for_task.
> 
> BUG=179923
> 
> 
> Review URL: https://chromiumcodereview.appspot.com/13845008

TBR=rsesek@chromium.org
Review URL: https://codereview.chromium.org/14120002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@193511 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 18 insertions, 18 deletions

diff --git a/content/browser/child_process_launcher.cc b/content/browser/child_process_launcher.cc
index bde7f93..66e7c83 100644
--- a/content/browser/child_process_launcher.cc
+++ b/content/browser/child_process_launcher.cc
@@ -266,30 +266,30 @@ class ChildProcessLauncher::Context
       options.fds_to_remap = &fds_to_map;
 
 #if defined(OS_MACOSX)
-      // Hold the MachBroker lock for the duration of LaunchProcess. The child
-      // will send its task port to the parent almost immediately after startup.
-      // The Mach message will be delivered to the parent, but updating the
-      // record of the launch will wait until after the placeholder PID is
-      // inserted below. This ensures that while the child process may send its
-      // port to the parent prior to the parent leaving LaunchProcess, the
-      // order in which the record in MachBroker is updated is correct.
-      MachBroker* broker = MachBroker::GetInstance();
-      broker->GetLock().Acquire();
-
-      // Make sure the MachBroker is running, and inform it to expect a
-      // check-in from the new process.
-      broker->EnsureRunning();
+      // Use synchronization to make sure that the MachBroker is ready to
+      // receive a check-in from the new process before the new process
+      // actually tries to check in.
+      base::LaunchSynchronizationHandle synchronization_handle;
+      options.synchronize = &synchronization_handle;
 #endif  // defined(OS_MACOSX)
 
       bool launched = base::LaunchProcess(*cmd_line, options, &handle);
 
 #if defined(OS_MACOSX)
-      if (launched)
-        broker->AddPlaceholderForPid(handle);
+      if (launched) {
+        MachBroker* broker = MachBroker::GetInstance();
+        {
+          base::AutoLock lock(broker->GetLock());
+
+          // Make sure the MachBroker is running, and inform it to expect a
+          // check-in from the new process.
+          broker->EnsureRunning();
+          broker->AddPlaceholderForPid(handle);
+        }
 
-      // After updating the broker, release the lock and let the child's
-      // messasge be processed on the broker's thread.
-      broker->GetLock().Release();
+        // Now that the MachBroker is ready, the child may continue.
+        base::LaunchSynchronize(synchronization_handle);
+      }
 #endif  // defined(OS_MACOSX)
 
       if (!launched)