1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "remoting/host/plugin/host_log_handler.h" 6 7 #include "base/lazy_instance.h" 8 #include "remoting/base/util.h" 9 #include "remoting/host/plugin/host_script_object.h" 10 11 namespace remoting { 12 13 // Records whether or not we have a scriptable object registered for logging. 14 // This is set inside the lock, but is read (in LogToUI) outside of a lock so 15 // that we don't needlessly slow down the system when we log. 16 static bool g_has_logging_scriptable_object = false; 17 18 // The lock that protects the logging globals. 19 static base::LazyInstance<base::Lock>::Leaky 20 g_logging_lock = LAZY_INSTANCE_INITIALIZER; 21 22 // The scriptable object that will display the log information to the user. 23 static HostNPScriptObject* g_logging_scriptable_object = NULL; 24 25 // The previously registered LogMessageHandler. If not NULL, we call this after 26 // we're doing processing the log message. 27 static logging::LogMessageHandlerFunction g_logging_old_handler = NULL; 28 29 // Set to true when we register our global log handler so that we don't try 30 // to register it twice. 31 static bool g_has_registered_log_handler = false; 32 33 // static 34 void HostLogHandler::RegisterLogMessageHandler() { 35 base::AutoLock lock(g_logging_lock.Get()); 36 37 if (g_has_registered_log_handler) 38 return; 39 40 LOG(INFO) << "Registering global log handler"; 41 42 // Record previous handler so we can call it in a chain. 43 g_logging_old_handler = logging::GetLogMessageHandler(); 44 45 // Set up log message handler. 46 // This is not thread-safe so we need it within our lock. 47 // Note that this will not log anything until a scriptable object instance 48 // has been created to handle the log message display. 49 logging::SetLogMessageHandler(&LogToUI); 50 g_has_registered_log_handler = true; 51 } 52 53 // static 54 void HostLogHandler::RegisterLoggingScriptObject( 55 HostNPScriptObject* script_object) { 56 base::AutoLock lock(g_logging_lock.Get()); 57 58 VLOG(1) << "Registering log handler scriptable object"; 59 60 // Register this script object as the one that will handle all logging calls 61 // and display them to the user. 62 // If multiple plugins are run, then the last one registered will handle all 63 // logging for all instances. 64 g_logging_scriptable_object = script_object; 65 g_has_logging_scriptable_object = true; 66 } 67 68 // static 69 void HostLogHandler::UnregisterLoggingScriptObject( 70 HostNPScriptObject* script_object) { 71 base::AutoLock lock(g_logging_lock.Get()); 72 73 // Ignore unless we're the currently registered script object. 74 if (script_object != g_logging_scriptable_object) 75 return; 76 77 // Unregister this script object for logging. 78 g_has_logging_scriptable_object = false; 79 g_logging_scriptable_object = NULL; 80 81 VLOG(1) << "Unregistering log handler scriptable object"; 82 } 83 84 // static 85 bool HostLogHandler::LogToUI(int severity, const char* file, int line, 86 size_t message_start, 87 const std::string& str) { 88 // Note: We're reading |g_has_logging_scriptable_object| outside of a lock. 89 // This lockless read is done so that we don't needlessly slow down global 90 // logging with a lock for each log message. 91 // 92 // This lockless read is safe because: 93 // 94 // Misreading a false value (when it should be true) means that we'll simply 95 // skip processing a few log messages. 96 // 97 // Misreading a true value (when it should be false) means that we'll take 98 // the lock and check |g_logging_scriptable_object| unnecessarily. This is not 99 // problematic because we always set |g_logging_scriptable_object| inside a 100 // lock. 101 // 102 // Misreading an old cached value is also not problematic for the same 103 // reasons: a mis-read either skips a log message or causes us to take a lock 104 // unnecessarily. 105 if (g_has_logging_scriptable_object) { 106 base::AutoLock lock(g_logging_lock.Get()); 107 108 if (g_logging_scriptable_object) { 109 std::string message = remoting::GetTimestampString(); 110 message += (str.c_str() + message_start); 111 g_logging_scriptable_object->PostLogDebugInfo(message); 112 } 113 } 114 115 // Call the next log handler in the chain. 116 if (g_logging_old_handler) 117 return (g_logging_old_handler)(severity, file, line, message_start, str); 118 119 return false; 120 } 121 122 } // namespace remoting 123
