1 // Copyright 2016 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 #ifndef BASE_TRACE_EVENT_TRACE_CATEGORY_H_ 6 #define BASE_TRACE_EVENT_TRACE_CATEGORY_H_ 7 8 #include <stdint.h> 9 10 namespace base { 11 namespace trace_event { 12 13 // Captures the state of an invidivual trace category. Nothing except tracing 14 // internals (e.g., TraceLog) is supposed to have non-const Category pointers. 15 struct TraceCategory { 16 // The TRACE_EVENT macros should only use this value as a bool. 17 // These enum values are effectively a public API and third_party projects 18 // depend on their value. Hence, never remove or recycle existing bits, unless 19 // you are sure that all the third-party projects that depend on this have 20 // been updated. 21 enum StateFlags : uint8_t { 22 ENABLED_FOR_RECORDING = 1 << 0, 23 24 // Not used anymore. 25 DEPRECATED_ENABLED_FOR_MONITORING = 1 << 1, 26 DEPRECATED_ENABLED_FOR_EVENT_CALLBACK = 1 << 2, 27 28 ENABLED_FOR_ETW_EXPORT = 1 << 3, 29 ENABLED_FOR_FILTERING = 1 << 4 30 }; 31 32 static const TraceCategory* FromStatePtr(const uint8_t* state_ptr) { 33 static_assert( 34 offsetof(TraceCategory, state_) == 0, 35 "|state_| must be the first field of the TraceCategory class."); 36 return reinterpret_cast<const TraceCategory*>(state_ptr); 37 } 38 39 bool is_valid() const { return name_ != nullptr; } 40 void set_name(const char* name) { name_ = name; } 41 const char* name() const { 42 DCHECK(is_valid()); 43 return name_; 44 } 45 46 // TODO(primiano): This is an intermediate solution to deal with the fact that 47 // today TRACE_EVENT* macros cache the state ptr. They should just cache the 48 // full TraceCategory ptr, which is immutable, and use these helper function 49 // here. This will get rid of the need of this awkward ptr getter completely. 50 const uint8_t* state_ptr() const { 51 return const_cast<const uint8_t*>(&state_); 52 } 53 54 uint8_t state() const { 55 return *const_cast<volatile const uint8_t*>(&state_); 56 } 57 58 bool is_enabled() const { return state() != 0; } 59 60 void set_state(uint8_t state) { 61 *const_cast<volatile uint8_t*>(&state_) = state; 62 } 63 64 void clear_state_flag(StateFlags flag) { set_state(state() & (~flag)); } 65 void set_state_flag(StateFlags flag) { set_state(state() | flag); } 66 67 uint32_t enabled_filters() const { 68 return *const_cast<volatile const uint32_t*>(&enabled_filters_); 69 } 70 71 bool is_filter_enabled(size_t index) const { 72 DCHECK(index < sizeof(enabled_filters_) * 8); 73 return (enabled_filters() & (1 << index)) != 0; 74 } 75 76 void set_enabled_filters(uint32_t enabled_filters) { 77 *const_cast<volatile uint32_t*>(&enabled_filters_) = enabled_filters; 78 } 79 80 void reset_for_testing() { 81 set_state(0); 82 set_enabled_filters(0); 83 } 84 85 // These fields should not be accessed directly, not even by tracing code. 86 // The only reason why these are not private is because it makes it impossible 87 // to have a global array of TraceCategory in category_registry.cc without 88 // creating initializers. See discussion on goo.gl/qhZN94 and 89 // crbug.com/{660967,660828}. 90 91 // The enabled state. TRACE_EVENT* macros will capture events if any of the 92 // flags here are set. Since TRACE_EVENTx macros are used in a lot of 93 // fast-paths, accesses to this field are non-barriered and racy by design. 94 // This field is mutated when starting/stopping tracing and we don't care 95 // about missing some events. 96 uint8_t state_; 97 98 // When ENABLED_FOR_FILTERING is set, this contains a bitmap to the 99 // coressponding filter (see event_filters.h). 100 uint32_t enabled_filters_; 101 102 // TraceCategory group names are long lived static strings. 103 const char* name_; 104 }; 105 106 } // namespace trace_event 107 } // namespace base 108 109 #endif // BASE_TRACE_EVENT_TRACE_CATEGORY_H_ 110
