| /* |
| * Copyright (C) 2019 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef INCLUDE_PERFETTO_TRACING_INTERNAL_TRACING_TLS_H_ |
| #define INCLUDE_PERFETTO_TRACING_INTERNAL_TRACING_TLS_H_ |
| |
| #include <array> |
| #include <memory> |
| |
| #include "perfetto/tracing/internal/basic_types.h" |
| #include "perfetto/tracing/internal/data_source_internal.h" |
| #include "perfetto/tracing/platform.h" |
| |
| namespace perfetto { |
| |
| class TraceWriterBase; |
| |
| namespace internal { |
| |
| // Organization of the thread-local storage |
| // ---------------------------------------- |
| // First of all, remember the cardinality of the problem: at any point in time |
| // there are M data sources registered (i.e. number of subclasses of DataSource) |
| // and up to N concurrent instances for each data source, so up to M * N total |
| // data source instances around. |
| // Each data source instance can be accessed by T threads (no upper bound). |
| // We can safely put hard limits both to M and N (i.e. say that we support at |
| // most 32 data source types per process and up to 8 concurrent instances). |
| // |
| // We want to make it so from the Platform viewpoint, we use only one global |
| // TLS object, so T instances in total, one per thread, regardless of M and N. |
| // This allows to deal with at-thread-exit destruction only in one place, rather |
| // than N, M or M * N. |
| // |
| // Visually: |
| // [ Thread 1 ] [ Thread 2 ] [ Thread T ] |
| // +---------------+ +---------------+ +---------------+ |
| // Data source Foo | | | | | | |
| // Instance 1 | TLS | | TLS | | TLS | |
| // Instance 2 | Object | | Object | | Object | |
| // Instance 3 | | | | | | |
| // | | | | | | |
| // Data source Bar | | | | | | |
| // Instance 1 | | | | | | |
| // Instance 2 | | | | | | |
| // +---------------+ +---------------+ +---------------+ |
| // |
| // Each TLS Object is organized as an array of M DataSourceThreadLocalState. |
| // Each DSTLS itself is an array of up to N per-instance objects. |
| // The only per-instance object for now is the TraceWriter. |
| // So for each data source, for each instance, for each thread we keep one |
| // TraceWriter. |
| // The lookup is O(1): Given the TLS object, the TraceWriter is just tls[M][N]. |
| class TracingTLS : public Platform::ThreadLocalObject { |
| public: |
| ~TracingTLS() override; |
| |
| // This is checked against TraceMuxerImpl's global generation counter to |
| // handle destruction of TraceWriter(s) that belong to data sources that |
| // have been stopped. When the two numbers diverge, a scan of all the |
| // thread-local TraceWriter(s) is issued. |
| uint32_t generation = 0; |
| |
| // This flag is true while this thread is inside a trace point for any data |
| // source or in other delicate parts of the tracing machinery during which we |
| // should not try to trace. Used to prevent unexpected re-entrancy. |
| bool is_in_trace_point = false; |
| |
| // By default all data source instances have independent thread-local state |
| // (see above). |
| std::array<DataSourceThreadLocalState, kMaxDataSources> data_sources_tls{}; |
| |
| // Track event data sources, however, share the same thread-local state in |
| // order to be able to share trace writers and interning state across all |
| // track event categories. |
| DataSourceThreadLocalState track_event_tls{}; |
| }; |
| |
| struct ScopedReentrancyAnnotator { |
| ScopedReentrancyAnnotator(TracingTLS& root_tls) : root_tls_(root_tls) { |
| PERFETTO_DCHECK(!root_tls_.is_in_trace_point); |
| root_tls_.is_in_trace_point = true; |
| } |
| ~ScopedReentrancyAnnotator() { root_tls_.is_in_trace_point = false; } |
| |
| private: |
| TracingTLS& root_tls_; |
| }; |
| |
| } // namespace internal |
| } // namespace perfetto |
| |
| #endif // INCLUDE_PERFETTO_TRACING_INTERNAL_TRACING_TLS_H_ |