1 /*
2  *
3  * Copyright 2015 gRPC authors.
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  *     http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  *
17  */
18 
19 #ifndef GRPC_CORE_LIB_DEBUG_TRACE_H
20 #define GRPC_CORE_LIB_DEBUG_TRACE_H
21 
22 #include <grpc/support/port_platform.h>
23 
24 #include <stdbool.h>
25 
26 #include <grpc/support/atm.h>
27 
28 #include "src/core/lib/gprpp/global_config.h"
29 
30 GPR_GLOBAL_CONFIG_DECLARE_STRING(grpc_trace);
31 
32 // TODO(veblush): Remove this deprecated function once codes depending on this
33 // function are updated in the internal repo.
34 void grpc_tracer_init(const char* env_var_name);
35 
36 void grpc_tracer_init();
37 void grpc_tracer_shutdown(void);
38 
39 #if defined(__has_feature)
40 #if __has_feature(thread_sanitizer)
41 #define GRPC_THREADSAFE_TRACER
42 #endif
43 #endif
44 
45 namespace grpc_core {
46 
47 class TraceFlag;
48 class TraceFlagList {
49  public:
50   static bool Set(const char* name, bool enabled);
51   static void Add(TraceFlag* flag);
52 
53  private:
54   static void LogAllTracers();
55   static TraceFlag* root_tracer_;
56 };
57 
58 namespace testing {
59 void grpc_tracer_enable_flag(grpc_core::TraceFlag* flag);
60 }
61 
62 class TraceFlag {
63  public:
64   TraceFlag(bool default_enabled, const char* name);
65   // TraceFlag needs to be trivially destructible since it is used as global
66   // variable.
67   ~TraceFlag() = default;
68 
name()69   const char* name() const { return name_; }
70 
71 // Use the symbol GRPC_USE_TRACERS to determine if tracers will be enabled in
72 // opt builds (tracers are always on in dbg builds). The default in OSS is for
73 // tracers to be on since we support binary distributions of gRPC for the
74 // wrapped language (wr don't want to force recompilation to get tracing).
75 // Internally, however, for performance reasons, we compile them out by
76 // default, since internal build systems make recompiling trivial.
77 //
78 // Prefer GRPC_TRACE_FLAG_ENABLED() macro instead of using enabled() directly.
79 #define GRPC_USE_TRACERS  // tracers on by default in OSS
80 #if defined(GRPC_USE_TRACERS) || !defined(NDEBUG)
enabled()81   bool enabled() {
82 #ifdef GRPC_THREADSAFE_TRACER
83     return gpr_atm_no_barrier_load(&value_) != 0;
84 #else
85     return value_;
86 #endif  // GRPC_THREADSAFE_TRACER
87   }
88 #else
enabled()89   bool enabled() { return false; }
90 #endif /* defined(GRPC_USE_TRACERS) || !defined(NDEBUG) */
91 
92  private:
93   friend void grpc_core::testing::grpc_tracer_enable_flag(TraceFlag* flag);
94   friend class TraceFlagList;
95 
set_enabled(bool enabled)96   void set_enabled(bool enabled) {
97 #ifdef GRPC_THREADSAFE_TRACER
98     gpr_atm_no_barrier_store(&value_, enabled);
99 #else
100     value_ = enabled;
101 #endif
102   }
103 
104   TraceFlag* next_tracer_;
105   const char* const name_;
106 #ifdef GRPC_THREADSAFE_TRACER
107   gpr_atm value_;
108 #else
109   bool value_;
110 #endif
111 };
112 
113 #define GRPC_TRACE_FLAG_ENABLED(f) GPR_UNLIKELY((f).enabled())
114 
115 #ifndef NDEBUG
116 typedef TraceFlag DebugOnlyTraceFlag;
117 #else
118 class DebugOnlyTraceFlag {
119  public:
DebugOnlyTraceFlag(bool,const char *)120   constexpr DebugOnlyTraceFlag(bool /*default_enabled*/, const char* /*name*/) {
121   }
enabled()122   constexpr bool enabled() const { return false; }
name()123   constexpr const char* name() const { return "DebugOnlyTraceFlag"; }
124 
125  private:
set_enabled(bool)126   void set_enabled(bool /*enabled*/) {}
127 };
128 #endif
129 
130 }  // namespace grpc_core
131 
132 #endif /* GRPC_CORE_LIB_DEBUG_TRACE_H */
133