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Diffstat (limited to 'third_party/abseil-cpp/absl/strings/internal/cordz_info.h')
| -rw-r--r-- | third_party/abseil-cpp/absl/strings/internal/cordz_info.h | 298 |
1 files changed, 0 insertions, 298 deletions
diff --git a/third_party/abseil-cpp/absl/strings/internal/cordz_info.h b/third_party/abseil-cpp/absl/strings/internal/cordz_info.h deleted file mode 100644 index 026d5b9981..0000000000 --- a/third_party/abseil-cpp/absl/strings/internal/cordz_info.h +++ /dev/null @@ -1,298 +0,0 @@ -// 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. - -#ifndef ABSL_STRINGS_CORDZ_INFO_H_ -#define ABSL_STRINGS_CORDZ_INFO_H_ - -#include <atomic> -#include <cstdint> -#include <functional> - -#include "absl/base/config.h" -#include "absl/base/internal/raw_logging.h" -#include "absl/base/internal/spinlock.h" -#include "absl/base/thread_annotations.h" -#include "absl/strings/internal/cord_internal.h" -#include "absl/strings/internal/cordz_functions.h" -#include "absl/strings/internal/cordz_handle.h" -#include "absl/strings/internal/cordz_statistics.h" -#include "absl/strings/internal/cordz_update_tracker.h" -#include "absl/synchronization/mutex.h" -#include "absl/types/span.h" - -namespace absl { -ABSL_NAMESPACE_BEGIN -namespace cord_internal { - -// CordzInfo tracks a profiled Cord. Each of these objects can be in two places. -// If a Cord is alive, the CordzInfo will be in the global_cordz_infos map, and -// can also be retrieved via the linked list starting with -// global_cordz_infos_head and continued via the cordz_info_next() method. When -// a Cord has reached the end of its lifespan, the CordzInfo object will be -// migrated out of the global_cordz_infos list and the global_cordz_infos_map, -// and will either be deleted or appended to the global_delete_queue. If it is -// placed on the global_delete_queue, the CordzInfo object will be cleaned in -// the destructor of a CordzSampleToken object. -class ABSL_LOCKABLE CordzInfo : public CordzHandle { - public: - using MethodIdentifier = CordzUpdateTracker::MethodIdentifier; - - // TrackCord creates a CordzInfo instance which tracks important metrics of - // a sampled cord, and stores the created CordzInfo instance into `cord'. All - // CordzInfo instances are placed in a global list which is used to discover - // and snapshot all actively tracked cords. Callers are responsible for - // calling UntrackCord() before the tracked Cord instance is deleted, or to - // stop tracking the sampled Cord. Callers are also responsible for guarding - // changes to the 'tree' value of a Cord (InlineData.tree) through the Lock() - // and Unlock() calls. Any change resulting in a new tree value for the cord - // requires a call to SetCordRep() before the old tree has been unreffed - // and/or deleted. `method` identifies the Cord public API method initiating - // the cord to be sampled. - // Requires `cord` to hold a tree, and `cord.cordz_info()` to be null. - static void TrackCord(InlineData& cord, MethodIdentifier method); - - // Identical to TrackCord(), except that this function fills the - // `parent_stack` and `parent_method` properties of the returned CordzInfo - // instance from the provided `src` instance if `src` is sampled. - // This function should be used for sampling 'copy constructed' and 'copy - // assigned' cords. This function allows 'cord` to be already sampled, in - // which case the CordzInfo will be newly created from `src`. - static void TrackCord(InlineData& cord, const InlineData& src, - MethodIdentifier method); - - // Maybe sample the cord identified by 'cord' for method 'method'. - // Uses `cordz_should_profile` to randomly pick cords to be sampled, and if - // so, invokes `TrackCord` to start sampling `cord`. - static void MaybeTrackCord(InlineData& cord, MethodIdentifier method); - - // Maybe sample the cord identified by 'cord' for method 'method'. - // `src` identifies a 'parent' cord which is assigned to `cord`, typically the - // input cord for a copy constructor, or an assign method such as `operator=` - // `cord` will be sampled if (and only if) `src` is sampled. - // If `cord` is currently being sampled and `src` is not being sampled, then - // this function will stop sampling the cord and reset the cord's cordz_info. - // - // Previously this function defined that `cord` will be sampled if either - // `src` is sampled, or if `cord` is randomly picked for sampling. However, - // this can cause issues, as there may be paths where some cord is assigned an - // indirect copy of it's own value. As such a 'string of copies' would then - // remain sampled (`src.is_profiled`), then assigning such a cord back to - // 'itself' creates a cycle where the cord will converge to 'always sampled`. - // - // For example: - // - // Cord x; - // for (...) { - // // Copy ctor --> y.is_profiled := x.is_profiled | random(...) - // Cord y = x; - // ... - // // Assign x = y --> x.is_profiled = y.is_profiled | random(...) - // // ==> x.is_profiled |= random(...) - // // ==> x converges to 'always profiled' - // x = y; - // } - static void MaybeTrackCord(InlineData& cord, const InlineData& src, - MethodIdentifier method); - - // Stops tracking changes for a sampled cord, and deletes the provided info. - // This function must be called before the sampled cord instance is deleted, - // and before the root cordrep of the sampled cord is unreffed. - // This function may extend the lifetime of the cordrep in cases where the - // CordInfo instance is being held by a concurrent collection thread. - void Untrack(); - - // Invokes UntrackCord() on `info` if `info` is not null. - static void MaybeUntrackCord(CordzInfo* info); - - CordzInfo() = delete; - CordzInfo(const CordzInfo&) = delete; - CordzInfo& operator=(const CordzInfo&) = delete; - - // Retrieves the oldest existing CordzInfo. - static CordzInfo* Head(const CordzSnapshot& snapshot) - ABSL_NO_THREAD_SAFETY_ANALYSIS; - - // Retrieves the next oldest existing CordzInfo older than 'this' instance. - CordzInfo* Next(const CordzSnapshot& snapshot) const - ABSL_NO_THREAD_SAFETY_ANALYSIS; - - // Locks this instance for the update identified by `method`. - // Increases the count for `method` in `update_tracker`. - void Lock(MethodIdentifier method) ABSL_EXCLUSIVE_LOCK_FUNCTION(mutex_); - - // Unlocks this instance. If the contained `rep` has been set to null - // indicating the Cord has been cleared or is otherwise no longer sampled, - // then this method will delete this CordzInfo instance. - void Unlock() ABSL_UNLOCK_FUNCTION(mutex_); - - // Asserts that this CordzInfo instance is locked. - void AssertHeld() ABSL_ASSERT_EXCLUSIVE_LOCK(mutex_); - - // Updates the `rep` property of this instance. This methods is invoked by - // Cord logic each time the root node of a sampled Cord changes, and before - // the old root reference count is deleted. This guarantees that collection - // code can always safely take a reference on the tracked cord. - // Requires a lock to be held through the `Lock()` method. - // TODO(b/117940323): annotate with ABSL_EXCLUSIVE_LOCKS_REQUIRED once all - // Cord code is in a state where this can be proven true by the compiler. - void SetCordRep(CordRep* rep); - - // Returns the current `rep` property of this instance with a reference - // added, or null if this instance represents a cord that has since been - // deleted or untracked. - CordRep* RefCordRep() const ABSL_LOCKS_EXCLUDED(mutex_); - - // Returns the current value of `rep_` for testing purposes only. - CordRep* GetCordRepForTesting() const ABSL_NO_THREAD_SAFETY_ANALYSIS { - return rep_; - } - - // Sets the current value of `rep_` for testing purposes only. - void SetCordRepForTesting(CordRep* rep) ABSL_NO_THREAD_SAFETY_ANALYSIS { - rep_ = rep; - } - - // Returns the stack trace for where the cord was first sampled. Cords are - // potentially sampled when they promote from an inlined cord to a tree or - // ring representation, which is not necessarily the location where the cord - // was first created. Some cords are created as inlined cords, and only as - // data is added do they become a non-inlined cord. However, typically the - // location represents reasonably well where the cord is 'created'. - absl::Span<void* const> GetStack() const; - - // Returns the stack trace for a sampled cord's 'parent stack trace'. This - // value may be set if the cord is sampled (promoted) after being created - // from, or being assigned the value of an existing (sampled) cord. - absl::Span<void* const> GetParentStack() const; - - // Retrieves the CordzStatistics associated with this Cord. The statistics - // are only updated when a Cord goes through a mutation, such as an Append - // or RemovePrefix. - CordzStatistics GetCordzStatistics() const; - - private: - using SpinLock = absl::base_internal::SpinLock; - using SpinLockHolder = ::absl::base_internal::SpinLockHolder; - - // Global cordz info list. CordzInfo stores a pointer to the global list - // instance to harden against ODR violations. - struct List { - constexpr explicit List(absl::ConstInitType) - : mutex(absl::kConstInit, - absl::base_internal::SCHEDULE_COOPERATIVE_AND_KERNEL) {} - - SpinLock mutex; - std::atomic<CordzInfo*> head ABSL_GUARDED_BY(mutex){nullptr}; - }; - - static constexpr int kMaxStackDepth = 64; - - explicit CordzInfo(CordRep* rep, const CordzInfo* src, - MethodIdentifier method); - ~CordzInfo() override; - - // Sets `rep_` without holding a lock. - void UnsafeSetCordRep(CordRep* rep) ABSL_NO_THREAD_SAFETY_ANALYSIS; - - void Track(); - - // Returns the parent method from `src`, which is either `parent_method_` or - // `method_` depending on `parent_method_` being kUnknown. - // Returns kUnknown if `src` is null. - static MethodIdentifier GetParentMethod(const CordzInfo* src); - - // Fills the provided stack from `src`, copying either `parent_stack_` or - // `stack_` depending on `parent_stack_` being empty, returning the size of - // the parent stack. - // Returns 0 if `src` is null. - static int FillParentStack(const CordzInfo* src, void** stack); - - void ODRCheck() const { -#ifndef NDEBUG - ABSL_RAW_CHECK(list_ == &global_list_, "ODR violation in Cord"); -#endif - } - - // Non-inlined implementation of `MaybeTrackCord`, which is executed if - // either `src` is sampled or `cord` is sampled, and either untracks or - // tracks `cord` as documented per `MaybeTrackCord`. - static void MaybeTrackCordImpl(InlineData& cord, const InlineData& src, - MethodIdentifier method); - - ABSL_CONST_INIT static List global_list_; - List* const list_ = &global_list_; - - // ci_prev_ and ci_next_ require the global list mutex to be held. - // Unfortunately we can't use thread annotations such that the thread safety - // analysis understands that list_ and global_list_ are one and the same. - std::atomic<CordzInfo*> ci_prev_{nullptr}; - std::atomic<CordzInfo*> ci_next_{nullptr}; - - mutable absl::Mutex mutex_; - CordRep* rep_ ABSL_GUARDED_BY(mutex_); - - void* stack_[kMaxStackDepth]; - void* parent_stack_[kMaxStackDepth]; - const int stack_depth_; - const int parent_stack_depth_; - const MethodIdentifier method_; - const MethodIdentifier parent_method_; - CordzUpdateTracker update_tracker_; - const absl::Time create_time_; -}; - -inline ABSL_ATTRIBUTE_ALWAYS_INLINE void CordzInfo::MaybeTrackCord( - InlineData& cord, MethodIdentifier method) { - if (ABSL_PREDICT_FALSE(cordz_should_profile())) { - TrackCord(cord, method); - } -} - -inline ABSL_ATTRIBUTE_ALWAYS_INLINE void CordzInfo::MaybeTrackCord( - InlineData& cord, const InlineData& src, MethodIdentifier method) { - if (ABSL_PREDICT_FALSE(InlineData::is_either_profiled(cord, src))) { - MaybeTrackCordImpl(cord, src, method); - } -} - -inline ABSL_ATTRIBUTE_ALWAYS_INLINE void CordzInfo::MaybeUntrackCord( - CordzInfo* info) { - if (ABSL_PREDICT_FALSE(info)) { - info->Untrack(); - } -} - -inline void CordzInfo::AssertHeld() ABSL_ASSERT_EXCLUSIVE_LOCK(mutex_) { -#ifndef NDEBUG - mutex_.AssertHeld(); -#endif -} - -inline void CordzInfo::SetCordRep(CordRep* rep) { - AssertHeld(); - rep_ = rep; -} - -inline void CordzInfo::UnsafeSetCordRep(CordRep* rep) { rep_ = rep; } - -inline CordRep* CordzInfo::RefCordRep() const ABSL_LOCKS_EXCLUDED(mutex_) { - MutexLock lock(&mutex_); - return rep_ ? CordRep::Ref(rep_) : nullptr; -} - -} // namespace cord_internal -ABSL_NAMESPACE_END -} // namespace absl - -#endif // ABSL_STRINGS_CORDZ_INFO_H_ |