[tracing] Add filtering mode in TraceLog

base/trace_event/trace_log.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_TRACE_EVENT_TRACE_LOG_H_
 #define BASE_TRACE_EVENT_TRACE_LOG_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 26 matching lines @@
 
 struct BASE_EXPORT TraceLogStatus {
   TraceLogStatus();
   ~TraceLogStatus();
   uint32_t event_capacity;
   uint32_t event_count;
 };
 
 class BASE_EXPORT TraceLog : public MemoryDumpProvider {
  public:
-  enum Mode {
-    DISABLED = 0,
-    RECORDING_MODE
+  // Argument passed to TrcaeLog::SetEnabled.
+  enum Mode : uint8_t {
+    // RECORDING_MODE: Enables normal tracing (recording trace events in the
+    // trace buffer).
+    RECORDING_MODE = 1 << 0,
+    // FILTERING_MODE: Trace events are enabled just for filtering but not for
+    // recording. Only event filters config of |trace_config| argument is used.
+    FILTERING_MODE = 1 << 1
   };
 
   // The pointer returned from GetCategoryGroupEnabledInternal() points to a
   // value with zero or more of the following bits. Used in this class only.
   // The TRACE_EVENT macros should only use the value as a bool.
   // These values must be in sync with macro values in TraceEvent.h in Blink.
   enum CategoryGroupEnabledFlags {
     // Category group enabled for the recording mode.
     ENABLED_FOR_RECORDING = 1 << 0,
     // Category group enabled by SetEventCallbackEnabled().
@@ skipping 10 matching lines @@
   // reached. The known category groups are inserted into |category_groups|.
   void GetKnownCategoryGroups(std::vector<std::string>* category_groups);
 
   // Retrieves a copy (for thread-safety) of the current TraceConfig.
   TraceConfig GetCurrentTraceConfig() const;
 
   // Initializes the thread-local event buffer, if not already initialized and
   // if the current thread supports that (has a message loop).
   void InitializeThreadLocalEventBufferIfSupported();
 
-  // Enables normal tracing (recording trace events in the trace buffer).
   // See TraceConfig comments for details on how to control what categories
-  // will be traced. If tracing has already been enabled, |category_filter| will
-  // be merged into the current category filter.
-  void SetEnabled(const TraceConfig& trace_config, Mode mode);
+  // will be traced. SetDisabled must be called for each mode that is enabled.

[Primiano Tucci (use gerrit), 2016/10/12 17:50:18]

s/for each mode that is enabled./distinctly for each mode (recording or
filtering)/

[ssid, 2016/10/12 19:04:44]

Done.

+  // If tracing has already been enabled, category filter (enabled and disabled

[Primiano Tucci (use gerrit), 2016/10/12 17:50:18]

s/enabled/enabled for recording/

[ssid, 2016/10/12 19:04:44]

Done.

+  // categories) will be merged into the current category filter.
+  // Enabling RECORDING_MODE does not enable filters. Trace event filters will
+  // be used only if FILTERING_MODE is set on |modes|. Filters can be enabled
+  // only when FILTERING_MODE is disabled.

[Primiano Tucci (use gerrit), 2016/10/12 17:50:18]

I see what you mean here with this last sentence but I think should be worded
better, e.g.:
Conversely to RECORDING_MODE, FILTERING_MODE doesn't support upgrading, i.e.
filters can only be enabled if not previously enabled.

[ssid, 2016/10/12 19:04:44]

Done.

+  void SetEnabled(const TraceConfig& trace_config, uint8_t modes);
 
-  // Disables normal tracing for all categories.
+  // TODO(ssid): Remove the default SetEnabled and IsEnabled. They should take
+  // Mode as argument.
+
+  // Disables tracing for all categories for the specified |modes| only. Only
+  // RECORDING_MODE is taken as default |modes|.
   void SetDisabled();
+  void SetDisabled(uint8_t modes);
 
-  bool IsEnabled() { return mode_ != DISABLED; }
+  // Returns true if TraceLog is enabled on recording mode.
+  // Note: Returns false even if FILTERING_MODE is enabled.
+  bool IsEnabled() { return enabled_modes_ & RECORDING_MODE; }

[Primiano Tucci (use gerrit), 2016/10/12 17:50:17]

fortunately we don't have too many cases for this.
In a follow up patch can you please make this

bool IsEnabledFor(Mode mode) { return enabled_modes_ & mode)  and change the few
call sites?
Thisw ill bring a bit more of sanity :)

[ssid, 2016/10/12 19:04:44]

Yes, that is why I added a TODO on top to remove this function

+
+  // Returns a bitmap of enabled modes from TraceLog::Mode.
+  uint8_t enabled_modes() { return enabled_modes_; }
 
   // The number of times we have begun recording traces. If tracing is off,
   // returns -1. If tracing is on, then it returns the number of times we have
   // recorded a trace. By watching for this number to increment, you can
   // passively discover when a new trace has begun. This is then used to
   // implement the TRACE_EVENT_IS_NEW_TRACE() primitive.
   int GetNumTracesRecorded();
 
 #if defined(OS_ANDROID)
   void StartATrace();
@@ skipping 326 matching lines @@
   TraceBuffer* trace_buffer() const { return logged_events_.get(); }
   TraceBuffer* CreateTraceBuffer();
 
   std::string EventToConsoleMessage(unsigned char phase,
                                     const TimeTicks& timestamp,
                                     TraceEvent* trace_event);
 
   TraceEvent* AddEventToThreadSharedChunkWhileLocked(TraceEventHandle* handle,
                                                      bool check_buffer_is_full);
   void CheckIfBufferIsFullWhileLocked();
-  void SetDisabledWhileLocked();
+  void SetDisabledWhileLocked(uint8_t modes);
 
   TraceEvent* GetEventByHandleInternal(TraceEventHandle handle,
                                        OptionalAutoLock* lock);
 
   void FlushInternal(const OutputCallback& cb,
                      bool use_worker_thread,
                      bool discard_events);
 
   // |generation| is used in the following callbacks to check if the callback
   // is called for the flush of the current |logged_events_|.
@@ skipping 27 matching lines @@
   static const InternalTraceOptions kInternalEchoToConsole;
   static const InternalTraceOptions kInternalRecordAsMuchAsPossible;
   static const InternalTraceOptions kInternalEnableArgumentFilter;
 
   // This lock protects TraceLog member accesses (except for members protected
   // by thread_info_lock_) from arbitrary threads.
   mutable Lock lock_;
   // This lock protects accesses to thread_names_, thread_event_start_times_
   // and thread_colors_.
   Lock thread_info_lock_;
-  Mode mode_;
+  uint8_t enabled_modes_;  // See TraceLog::Mode.
   int num_traces_recorded_;
   std::unique_ptr<TraceBuffer> logged_events_;
   std::vector<std::unique_ptr<TraceEvent>> metadata_events_;
   subtle::AtomicWord /* EventCallback */ event_callback_;
   bool dispatching_to_observer_list_;
   std::vector<EnabledStateObserver*> enabled_state_observer_list_;
   std::map<AsyncEnabledStateObserver*, RegisteredAsyncObserver>
       async_observers_;
 
   std::string process_name_;
@@ skipping 17 matching lines @@
 
   // Allow tests to wake up when certain events occur.
   WatchEventCallback watch_event_callback_;
   subtle::AtomicWord /* const unsigned char* */ watch_category_;
   std::string watch_event_name_;
 
   subtle::AtomicWord /* Options */ trace_options_;
 
   TraceConfig trace_config_;
   TraceConfig event_callback_trace_config_;
+  TraceConfig::EventFilters event_filters_enabled_;
 
   ThreadLocalPointer<ThreadLocalEventBuffer> thread_local_event_buffer_;
   ThreadLocalBoolean thread_blocks_message_loop_;
   ThreadLocalBoolean thread_is_in_trace_event_;
 
   // Contains the message loops of threads that have had at least one event
   // added into the local event buffer. Not using SingleThreadTaskRunner
   // because we need to know the life time of the message loops.
   hash_set<MessageLoop*> thread_message_loops_;
 
   // For events which can't be added into the thread local buffer, e.g. events
   // from threads without a message loop.
   std::unique_ptr<TraceBufferChunk> thread_shared_chunk_;
   size_t thread_shared_chunk_index_;
 
   // Set when asynchronous Flush is in progress.
   OutputCallback flush_output_callback_;
   scoped_refptr<SingleThreadTaskRunner> flush_task_runner_;
   ArgumentFilterPredicate argument_filter_predicate_;
   subtle::AtomicWord generation_;
   bool use_worker_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(TraceLog);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_TRACE_LOG_H_