1 // Copyright 2016 The Chromium Authors 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 #include "base/check.h" 11 12 namespace base { 13 namespace trace_event { 14 15 // Captures the state of an invidivual trace category. Nothing except tracing 16 // internals (e.g., TraceLog) is supposed to have non-const Category pointers. 17 struct TraceCategory { 18 // The TRACE_EVENT macros should only use this value as a bool. 19 // These enum values are effectively a public API and third_party projects 20 // depend on their value. Hence, never remove or recycle existing bits, unless 21 // you are sure that all the third-party projects that depend on this have 22 // been updated. 23 enum StateFlags : uint8_t { 24 ENABLED_FOR_RECORDING = 1 << 0, 25 26 // Not used anymore. 27 DEPRECATED_ENABLED_FOR_MONITORING = 1 << 1, 28 DEPRECATED_ENABLED_FOR_EVENT_CALLBACK = 1 << 2, 29 30 ENABLED_FOR_ETW_EXPORT = 1 << 3, 31 ENABLED_FOR_FILTERING = 1 << 4 32 }; 33 FromStatePtrTraceCategory34 static const TraceCategory* FromStatePtr(const uint8_t* state_ptr) { 35 static_assert( 36 offsetof(TraceCategory, state_) == 0, 37 "|state_| must be the first field of the TraceCategory class."); 38 return reinterpret_cast<const TraceCategory*>(state_ptr); 39 } 40 is_validTraceCategory41 bool is_valid() const { return name_ != nullptr; } set_nameTraceCategory42 void set_name(const char* name) { name_ = name; } nameTraceCategory43 const char* name() const { 44 DCHECK(is_valid()); 45 return name_; 46 } 47 48 // TODO(primiano): This is an intermediate solution to deal with the fact that 49 // today TRACE_EVENT* macros cache the state ptr. They should just cache the 50 // full TraceCategory ptr, which is immutable, and use these helper function 51 // here. This will get rid of the need of this awkward ptr getter completely. state_ptrTraceCategory52 constexpr const uint8_t* state_ptr() const { 53 return const_cast<const uint8_t*>(&state_); 54 } 55 stateTraceCategory56 uint8_t state() const { 57 return *const_cast<volatile const uint8_t*>(&state_); 58 } 59 is_enabledTraceCategory60 bool is_enabled() const { return state() != 0; } 61 set_stateTraceCategory62 void set_state(uint8_t state) { 63 *const_cast<volatile uint8_t*>(&state_) = state; 64 } 65 clear_state_flagTraceCategory66 void clear_state_flag(StateFlags flag) { set_state(state() & (~flag)); } set_state_flagTraceCategory67 void set_state_flag(StateFlags flag) { set_state(state() | flag); } 68 enabled_filtersTraceCategory69 uint32_t enabled_filters() const { 70 return *const_cast<volatile const uint32_t*>(&enabled_filters_); 71 } 72 is_filter_enabledTraceCategory73 bool is_filter_enabled(size_t index) const { 74 DCHECK(index < sizeof(enabled_filters_) * 8); 75 return (enabled_filters() & (1 << index)) != 0; 76 } 77 set_enabled_filtersTraceCategory78 void set_enabled_filters(uint32_t enabled_filters) { 79 *const_cast<volatile uint32_t*>(&enabled_filters_) = enabled_filters; 80 } 81 reset_for_testingTraceCategory82 void reset_for_testing() { 83 set_state(0); 84 set_enabled_filters(0); 85 } 86 87 // These fields should not be accessed directly, not even by tracing code. 88 // The only reason why these are not private is because it makes it impossible 89 // to have a global array of TraceCategory in category_registry.cc without 90 // creating initializers. See discussion on goo.gl/qhZN94 and 91 // crbug.com/{660967,660828}. 92 93 // The enabled state. TRACE_EVENT* macros will capture events if any of the 94 // flags here are set. Since TRACE_EVENTx macros are used in a lot of 95 // fast-paths, accesses to this field are non-barriered and racy by design. 96 // This field is mutated when starting/stopping tracing and we don't care 97 // about missing some events. 98 uint8_t state_; 99 100 // When ENABLED_FOR_FILTERING is set, this contains a bitmap to the 101 // corresponding filter (see event_filters.h). 102 uint32_t enabled_filters_; 103 104 // TraceCategory group names are long lived static strings. 105 const char* name_; 106 }; 107 108 } // namespace trace_event 109 } // namespace base 110 111 #endif // BASE_TRACE_EVENT_TRACE_CATEGORY_H_ 112