[Mac] Replace the existing browser-child mach ipc with a long-lived listener ...

chrome/browser/mach_broker_mac.cc

Index: chrome/browser/mach_broker_mac.cc
===================================================================
--- chrome/browser/mach_broker_mac.cc	(revision 59759)
+++ chrome/browser/mach_broker_mac.cc	(working copy)
@@ -4,13 +4,26 @@
 
 #include "chrome/browser/mach_broker_mac.h"
 
+#include "base/command_line.h"
 #include "base/logging.h"
+#include "base/mach_ipc_mac.h"
+#include "base/platform_thread.h"
+#include "base/string_util.h"
+#include "base/sys_string_conversions.h"
 #include "chrome/browser/chrome_thread.h"
 #include "chrome/browser/extensions/extension_host.h"
 #include "chrome/browser/renderer_host/render_process_host.h"
 #include "chrome/common/child_process_info.h"
+#include "chrome/common/chrome_switches.h"
 #include "chrome/common/notification_service.h"
 
+namespace {
+// Prints a string representation of a Mach error code.
+std::string MachErrorCode(kern_return_t err) {
+  return StringPrintf("0x%x %s", err, mach_error_string(err));
+}
+}  // namespace
+
 // Required because notifications happen on the UI thread.
 class RegisterNotificationTask : public Task {
  public:
@@ -38,28 +51,124 @@
 
  private:
   MachBroker* broker_;
+  DISALLOW_COPY_AND_ASSIGN(RegisterNotificationTask);
 };
 
-MachBroker::MachBroker() {
-  ChromeThread::PostTask(
-      ChromeThread::UI, FROM_HERE, new RegisterNotificationTask(this));
-}
+class MachListenerThreadDelegate : public PlatformThread::Delegate {
+ public:
+  MachListenerThreadDelegate(MachBroker* broker) : broker_(broker) {
+    DCHECK(broker_);
+    std::string port_name = MachBroker::GetMachPortName();
 
+    // Create the receive port in the constructor, not in ThreadMain().  It is
+    // important to create and register the receive port before starting the
+    // thread so that child processes will always have someone who's listening.
+    receive_port_.reset(new base::ReceivePort(port_name.c_str()));
+  }
+
+  // Implement |PlatformThread::Delegate|.
+  void ThreadMain() {
+    base::MachReceiveMessage message;
+    kern_return_t err;
+    while ((err = receive_port_->WaitForMessage(&message,
+                                                MACH_MSG_TIMEOUT_NONE)) ==
+           KERN_SUCCESS) {
+      // 0 was the secret message id.  Reject any messages that don't have it.
+      if (message.GetMessageID() != 0) {
+        LOG(ERROR) << "Received message with incorrect id: "
+                   << message.GetMessageID();
+        continue;
+      }
+
+      const task_t child_task = message.GetTranslatedPort(0);
+      if (child_task == MACH_PORT_NULL) {
+        LOG(ERROR) << "parent GetTranslatedPort(0) failed.";
+        continue;
+      }
+
+      // It is possible for the child process to die after the call to
+      // |pid_for_task()| but before the call to |FinalizePid()|.  To prevent
+      // leaking MachBroker map entries in this case, lock around both these
+      // calls.  If the child dies, the death notification will be processed
+      // after the call to FinalizePid(), ensuring proper cleanup.
+      AutoLock lock(broker_->GetLock());
+
+      int pid;
+      err = pid_for_task(child_task, &pid);
+      if (err == KERN_SUCCESS) {
+        broker_->FinalizePid(pid,
+                             MachBroker::MachInfo().SetTask(child_task));
+      } else {
+        LOG(ERROR) << "Error getting pid for task " << child_task
+                   << ": " << MachErrorCode(err);
+      }
+    }
+
+    LOG(ERROR) << "Mach listener thread exiting; "
+               << "parent WaitForMessage() likely failed: "
+               << MachErrorCode(err);
+  }
+
+ private:
+  // The Mach port to listen on.  Created on thread startup.
+  scoped_ptr<base::ReceivePort> receive_port_;
+
+  // The MachBroker to use when new child task rights are received.  Can be
+  // NULL.
+  MachBroker* broker_;  // weak
+
+  DISALLOW_COPY_AND_ASSIGN(MachListenerThreadDelegate);
+};
+
 // Returns the global MachBroker.
 MachBroker* MachBroker::instance() {
-  return Singleton<MachBroker>::get();
+  return Singleton<MachBroker, LeakySingletonTraits<MachBroker> >::get();
 }
 
-// Adds mach info for a given pid.
-void MachBroker::RegisterPid(
-    base::ProcessHandle pid, const MachInfo& mach_info) {
-  AutoLock lock(lock_);
+MachBroker::MachBroker() : listener_thread_started_(false) {
+}
+
+void MachBroker::PrepareForFork() {
+  if (!listener_thread_started_) {
+    listener_thread_started_ = true;
+
+    ChromeThread::PostTask(
+        ChromeThread::UI, FROM_HERE, new RegisterNotificationTask(this));
+
+    // Intentional leak.  This thread is never joined or reaped.
+    PlatformThread::CreateNonJoinable(0, new MachListenerThreadDelegate(this));
+  }
+}
+
+// Adds a placeholder to the map for the given pid with MACH_PORT_NULL.
+void MachBroker::AddPlaceholderForPid(base::ProcessHandle pid) {
+  lock_.AssertAcquired();
+
+  MachInfo mach_info;
   DCHECK_EQ(0u, mach_map_.count(pid));
   mach_map_[pid] = mach_info;
 }
 
+// Updates the mapping for |pid| to include the given |mach_info|.
+void MachBroker::FinalizePid(base::ProcessHandle pid,
+                             const MachInfo& mach_info) {
+  lock_.AssertAcquired();
+
+  const int count = mach_map_.count(pid);
+  if (count == 0) {
+    // Do nothing for unknown pids.
+    LOG(ERROR) << "Unknown process " << pid << " is sending Mach IPC messages!";
+    return;
+  }
+
+  DCHECK_EQ(1, count);
+  DCHECK(mach_map_[pid].mach_task_ == MACH_PORT_NULL);
+  if (mach_map_[pid].mach_task_ == MACH_PORT_NULL)
+    mach_map_[pid] = mach_info;
+}
+
 // Removes all mappings belonging to |pid| from the broker.
-void MachBroker::Invalidate(base::ProcessHandle pid) {
+void MachBroker::InvalidatePid(base::ProcessHandle pid) {
   AutoLock lock(lock_);
   MachBroker::MachMap::iterator it = mach_map_.find(pid);
   if (it == mach_map_.end())
@@ -69,10 +178,14 @@
                                           it->second.mach_task_);
   LOG_IF(WARNING, kr != KERN_SUCCESS)
      << "Failed to mach_port_deallocate mach task " << it->second.mach_task_
-     << ", error " << kr;
+     << ", error " << MachErrorCode(kr);
   mach_map_.erase(it);
 }
 
+Lock& MachBroker::GetLock() {
+  return lock_;
+}
+
 // Returns the mach task belonging to |pid|.
 mach_port_t MachBroker::TaskForPid(base::ProcessHandle pid) const {
   AutoLock lock(lock_);
@@ -85,6 +198,9 @@
 void MachBroker::Observe(NotificationType type,
                          const NotificationSource& source,
                          const NotificationDetails& details) {
+  // TODO(rohitrao): These notifications do not always carry the proper PIDs,
+  // especially when the renderer is already gone or has crashed.  Find a better
+  // way to listen for child process deaths.  http://crbug.com/55734
   base::ProcessHandle handle = 0;
   switch (type.value) {
     case NotificationType::RENDERER_PROCESS_CLOSED:
@@ -103,5 +219,23 @@
       NOTREACHED() << "Unexpected notification";
       break;
   }
-  Invalidate(handle);
+  InvalidatePid(handle);
 }
+
+// static
+std::string MachBroker::GetMachPortName() {
+  static const char kFormatString[] =
+#if defined(GOOGLE_CHROME_BUILD)
+      "com.google.Chrome"
+#else
+      "org.chromium.Chromium"
+#endif
+      ".rohitfork.%d";
+
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+  const bool is_child = command_line.HasSwitch(switches::kProcessType);
+
+  // In non-browser (child) processes, use the parent's pid.
+  const pid_t pid = is_child ? getppid() : getpid();
+  return StringPrintf(kFormatString, pid);
+}