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author | Colin Cross <ccross@android.com> | 2022-04-13 03:15:00 +0000 |
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committer | Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com> | 2022-04-13 03:15:00 +0000 |
commit | 6c9587948173932b64d97c288a947e43d2a2ac14 (patch) | |
tree | 2ce94d7f0804ccb77d1fa9b2a1bca00eecdff1e2 /third_party/abseil-cpp/absl/strings/internal/cordz_sample_token.h | |
parent | f60eaea2240ba9e1c508e8e0c91d39ee9fc47be5 (diff) | |
parent | 43d8f56cdc20240b37c36bf417dd0d6999bce738 (diff) | |
download | webrtc-6c9587948173932b64d97c288a947e43d2a2ac14.tar.gz |
Merge changes I0ab600cd,I1e74c64a am: 798f3afdf6 am: 2f9c4b2c3b am: a9167328fc am: 7563023510 am: 43d8f56cdcandroid-13.0.0_r83android-13.0.0_r82android-13.0.0_r81android-13.0.0_r80android-13.0.0_r79android-13.0.0_r78android-13.0.0_r77android-13.0.0_r76android-13.0.0_r75android-13.0.0_r74android-13.0.0_r73android-13.0.0_r72android-13.0.0_r71android-13.0.0_r70android-13.0.0_r69android-13.0.0_r68android-13.0.0_r67android-13.0.0_r66android-13.0.0_r65android-13.0.0_r64android-13.0.0_r63android-13.0.0_r62android-13.0.0_r61android-13.0.0_r60android-13.0.0_r59android-13.0.0_r58android-13.0.0_r56android-13.0.0_r54android-13.0.0_r53android-13.0.0_r52android-13.0.0_r51android-13.0.0_r50android-13.0.0_r49android-13.0.0_r48android-13.0.0_r47android-13.0.0_r46android-13.0.0_r45android-13.0.0_r44android-13.0.0_r43android-13.0.0_r42android-13.0.0_r41android-13.0.0_r40android-13.0.0_r39android-13.0.0_r38android-13.0.0_r37android-13.0.0_r36android-13.0.0_r35android-13.0.0_r34android-13.0.0_r33android-13.0.0_r32android13-qpr3-s9-releaseandroid13-qpr3-s8-releaseandroid13-qpr3-s7-releaseandroid13-qpr3-s6-releaseandroid13-qpr3-s5-releaseandroid13-qpr3-s4-releaseandroid13-qpr3-s3-releaseandroid13-qpr3-s2-releaseandroid13-qpr3-s14-releaseandroid13-qpr3-s13-releaseandroid13-qpr3-s12-releaseandroid13-qpr3-s11-releaseandroid13-qpr3-s10-releaseandroid13-qpr3-s1-releaseandroid13-qpr3-releaseandroid13-qpr3-c-s8-releaseandroid13-qpr3-c-s7-releaseandroid13-qpr3-c-s6-releaseandroid13-qpr3-c-s5-releaseandroid13-qpr3-c-s4-releaseandroid13-qpr3-c-s3-releaseandroid13-qpr3-c-s2-releaseandroid13-qpr3-c-s12-releaseandroid13-qpr3-c-s11-releaseandroid13-qpr3-c-s10-releaseandroid13-qpr3-c-s1-releaseandroid13-qpr2-s9-releaseandroid13-qpr2-s8-releaseandroid13-qpr2-s7-releaseandroid13-qpr2-s6-releaseandroid13-qpr2-s5-releaseandroid13-qpr2-s3-releaseandroid13-qpr2-s2-releaseandroid13-qpr2-s12-releaseandroid13-qpr2-s11-releaseandroid13-qpr2-s10-releaseandroid13-qpr2-s1-releaseandroid13-qpr2-releaseandroid13-qpr2-b-s1-releaseandroid13-d4-s2-releaseandroid13-d4-s1-releaseandroid13-d4-release
Original change: https://android-review.googlesource.com/c/platform/external/webrtc/+/2062410
Change-Id: I1aa9f459b825711b800cc65782979943a9151ec7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
Diffstat (limited to 'third_party/abseil-cpp/absl/strings/internal/cordz_sample_token.h')
-rw-r--r-- | third_party/abseil-cpp/absl/strings/internal/cordz_sample_token.h | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/third_party/abseil-cpp/absl/strings/internal/cordz_sample_token.h b/third_party/abseil-cpp/absl/strings/internal/cordz_sample_token.h new file mode 100644 index 0000000000..28a1d70ccc --- /dev/null +++ b/third_party/abseil-cpp/absl/strings/internal/cordz_sample_token.h @@ -0,0 +1,97 @@ +// Copyright 2019 The Abseil Authors. +// +// 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 +// +// https://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. + +#include "absl/base/config.h" +#include "absl/strings/internal/cordz_handle.h" +#include "absl/strings/internal/cordz_info.h" + +#ifndef ABSL_STRINGS_CORDZ_SAMPLE_TOKEN_H_ +#define ABSL_STRINGS_CORDZ_SAMPLE_TOKEN_H_ + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace cord_internal { + +// The existence of a CordzSampleToken guarantees that a reader can traverse the +// global_cordz_infos_head linked-list without needing to hold a mutex. When a +// CordzSampleToken exists, all CordzInfo objects that would be destroyed are +// instead appended to a deletion queue. When the CordzSampleToken is destroyed, +// it will also clean up any of these CordzInfo objects. +// +// E.g., ST are CordzSampleToken objects and CH are CordzHandle objects. +// ST1 <- CH1 <- CH2 <- ST2 <- CH3 <- global_delete_queue_tail +// +// This list tracks that CH1 and CH2 were created after ST1, so the thread +// holding ST1 might have a referece to CH1, CH2, ST2, and CH3. However, ST2 was +// created later, so the thread holding the ST2 token cannot have a reference to +// ST1, CH1, or CH2. If ST1 is cleaned up first, that thread will delete ST1, +// CH1, and CH2. If instead ST2 is cleaned up first, that thread will only +// delete ST2. +// +// If ST1 is cleaned up first, the new list will be: +// ST2 <- CH3 <- global_delete_queue_tail +// +// If ST2 is cleaned up first, the new list will be: +// ST1 <- CH1 <- CH2 <- CH3 <- global_delete_queue_tail +// +// All new CordzHandle objects are appended to the list, so if a new thread +// comes along before either ST1 or ST2 are cleaned up, the new list will be: +// ST1 <- CH1 <- CH2 <- ST2 <- CH3 <- ST3 <- global_delete_queue_tail +// +// A thread must hold the global_delete_queue_mu mutex whenever it's altering +// this list. +// +// It is safe for thread that holds a CordzSampleToken to read +// global_cordz_infos at any time since the objects it is able to retrieve will +// not be deleted while the CordzSampleToken exists. +class CordzSampleToken : public CordzSnapshot { + public: + class Iterator { + public: + using iterator_category = std::input_iterator_tag; + using value_type = const CordzInfo&; + using difference_type = ptrdiff_t; + using pointer = const CordzInfo*; + using reference = value_type; + + Iterator() = default; + + Iterator& operator++(); + Iterator operator++(int); + friend bool operator==(const Iterator& lhs, const Iterator& rhs); + friend bool operator!=(const Iterator& lhs, const Iterator& rhs); + reference operator*() const; + pointer operator->() const; + + private: + friend class CordzSampleToken; + explicit Iterator(const CordzSampleToken* token); + + const CordzSampleToken* token_ = nullptr; + pointer current_ = nullptr; + }; + + CordzSampleToken() = default; + CordzSampleToken(const CordzSampleToken&) = delete; + CordzSampleToken& operator=(const CordzSampleToken&) = delete; + + Iterator begin() { return Iterator(this); } + Iterator end() { return Iterator(); } +}; + +} // namespace cord_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_STRINGS_CORDZ_SAMPLE_TOKEN_H_ |