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diff --git a/third_party/abseil-cpp/absl/strings/internal/cordz_handle.h b/third_party/abseil-cpp/absl/strings/internal/cordz_handle.h
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+++ b/third_party/abseil-cpp/absl/strings/internal/cordz_handle.h
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+// 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_HANDLE_H_
+#define ABSL_STRINGS_CORDZ_HANDLE_H_
+
+#include <atomic>
+#include <vector>
+
+#include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/base/internal/spinlock.h"
+#include "absl/synchronization/mutex.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace cord_internal {
+
+// This base class allows multiple types of object (CordzInfo and
+// CordzSampleToken) to exist simultaneously on the delete queue (pointed to by
+// global_dq_tail and traversed using dq_prev_ and dq_next_). The
+// delete queue guarantees that once a profiler creates a CordzSampleToken and
+// has gained visibility into a CordzInfo object, that CordzInfo object will not
+// be deleted prematurely. This allows the profiler to inspect all CordzInfo
+// objects that are alive without needing to hold a global lock.
+class CordzHandle {
+ public:
+  CordzHandle() : CordzHandle(false) {}
+
+  bool is_snapshot() const { return is_snapshot_; }
+
+  // Returns true if this instance is safe to be deleted because it is either a
+  // snapshot, which is always safe to delete, or not included in the global
+  // delete queue and thus not included in any snapshot.
+  // Callers are responsible for making sure this instance can not be newly
+  // discovered by other threads. For example, CordzInfo instances first de-list
+  // themselves from the global CordzInfo list before determining if they are
+  // safe to be deleted directly.
+  // If SafeToDelete returns false, callers MUST use the Delete() method to
+  // safely queue CordzHandle instances for deletion.
+  bool SafeToDelete() const;
+
+  // Deletes the provided instance, or puts it on the delete queue to be deleted
+  // once there are no more sample tokens (snapshot) instances potentially
+  // referencing the instance. `handle` should not be null.
+  static void Delete(CordzHandle* handle);
+
+  // Returns the current entries in the delete queue in LIFO order.
+  static std::vector<const CordzHandle*> DiagnosticsGetDeleteQueue();
+
+  // Returns true if the provided handle is nullptr or guarded by this handle.
+  // Since the CordzSnapshot token is itself a CordzHandle, this method will
+  // allow tests to check if that token is keeping an arbitrary CordzHandle
+  // alive.
+  bool DiagnosticsHandleIsSafeToInspect(const CordzHandle* handle) const;
+
+  // Returns the current entries in the delete queue, in LIFO order, that are
+  // protected by this. CordzHandle objects are only placed on the delete queue
+  // after CordzHandle::Delete is called with them as an argument. Only
+  // CordzHandle objects that are not also CordzSnapshot objects will be
+  // included in the return vector. For each of the handles in the return
+  // vector, the earliest that their memory can be freed is when this
+  // CordzSnapshot object is deleted.
+  std::vector<const CordzHandle*> DiagnosticsGetSafeToInspectDeletedHandles();
+
+ protected:
+  explicit CordzHandle(bool is_snapshot);
+  virtual ~CordzHandle();
+
+ private:
+  // Global queue data. CordzHandle stores a pointer to the global queue
+  // instance to harden against ODR violations.
+  struct Queue {
+    constexpr explicit Queue(absl::ConstInitType)
+        : mutex(absl::kConstInit,
+                absl::base_internal::SCHEDULE_COOPERATIVE_AND_KERNEL) {}
+
+    absl::base_internal::SpinLock mutex;
+    std::atomic<CordzHandle*> dq_tail ABSL_GUARDED_BY(mutex){nullptr};
+
+    // Returns true if this delete queue is empty. This method does not acquire
+    // the lock, but does a 'load acquire' observation on the delete queue tail.
+    // It is used inside Delete() to check for the presence of a delete queue
+    // without holding the lock. The assumption is that the caller is in the
+    // state of 'being deleted', and can not be newly discovered by a concurrent
+    // 'being constructed' snapshot instance. Practically, this means that any
+    // such discovery (`find`, 'first' or 'next', etc) must have proper 'happens
+    // before / after' semantics and atomic fences.
+    bool IsEmpty() const ABSL_NO_THREAD_SAFETY_ANALYSIS {
+      return dq_tail.load(std::memory_order_acquire) == nullptr;
+    }
+  };
+
+  void ODRCheck() const {
+#ifndef NDEBUG
+    ABSL_RAW_CHECK(queue_ == &global_queue_, "ODR violation in Cord");
+#endif
+  }
+
+  ABSL_CONST_INIT static Queue global_queue_;
+  Queue* const queue_ = &global_queue_;
+  const bool is_snapshot_;
+
+  // dq_prev_ and dq_next_ require the global queue mutex to be held.
+  // Unfortunately we can't use thread annotations such that the thread safety
+  // analysis understands that queue_ and global_queue_ are one and the same.
+  CordzHandle* dq_prev_  = nullptr;
+  CordzHandle* dq_next_ = nullptr;
+};
+
+class CordzSnapshot : public CordzHandle {
+ public:
+  CordzSnapshot() : CordzHandle(true) {}
+};
+
+}  // namespace cord_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_CORDZ_HANDLE_H_