crash-reporter: avoid deadlock if dbus-daemon is hanging

crash_reporter.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <string>
 
 #include "base/file_util.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/string_util.h"
@@ skipping 49 matching lines @@
   s_metrics_lib.SendEnumToUMA(std::string(kCrashCounterHistogram),
                               kCrashKindUncleanShutdown,
                               kCrashKindMax);
 }
 
 static void CountUserCrash() {
   s_metrics_lib.SendEnumToUMA(std::string(kCrashCounterHistogram),
                               kCrashKindUser,
                               kCrashKindMax);
   std::string command = StringPrintf(
-      "/usr/bin/dbus-send --type=signal --system / \"%s\"",
+      "/usr/bin/dbus-send --type=signal --system / \"%s\" &",
       kUserCrashSignal);
   // Announce through D-Bus whenever a user crash happens. This is
   // used by the metrics daemon to log active use time between
   // crashes.
   //
   // This could be done more efficiently by explicit fork/exec or
   // using a dbus library directly. However, this should run
   // relatively rarely and longer term we may need to implement a
   // better way to do this that doesn't rely on D-Bus.
+  //
+  // We run in the background in case dbus daemon itself is crashed
+  // and not responding.  This allows us to not block and potentially
+  // deadlock on a dbus-daemon crash.  If dbus-daemon crashes without
+  // restarting, each crash will fork off a lot of dbus-send
+  // processes.  Such a system is in a unusable state and will need
+  // to be restarted anyway.
 
-  int status __attribute__((unused)) = system(command.c_str());
+  int status = system(command.c_str());
+  if (status != 0) {
+    s_system_log.LogWarning("dbus-send running failed");
+  }
 }
 
 static int Initialize(KernelCollector *kernel_collector,
                       UserCollector *user_collector,
                       UncleanShutdownCollector *unclean_shutdown_collector) {
   CHECK(!FLAGS_clean_shutdown) << "Incompatible options";
 
   bool was_kernel_crash = false;
   bool was_unclean_shutdown = false;
   kernel_collector->Enable();
@@ skipping 78 matching lines @@
   }
 
   if (FLAGS_clean_shutdown) {
     unclean_shutdown_collector.Disable();
     user_collector.Disable();
     return 0;
   }
 
   return HandleUserCrash(&user_collector);
 }