Export of internal Abseil changes

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17141711ee419daa597a9f31e73721f80143e55a by Gennadiy Rozental <rogeeff@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 401384949

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ac48584a7b16e8a12e26d49deb6cddec584a20b5 by Derek Mauro <dmauro@google.com>:

Internal change

PiperOrigin-RevId: 401337785

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8a51bb7c962845e0707240c5ba12c1b80f6fbbe9 by Derek Mauro <dmauro@google.com>:

Internal change

PiperOrigin-RevId: 401047691

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8e18024510869247f3c04c7807c93709eca2322a by Chris Kennelly <ckennelly@google.com>:

Note that SpinLock does not guarantee priorities for wakeups.

PiperOrigin-RevId: 400999238

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75bc09b5f95fbb74b74d14c370bfb80011e8fb7f by Derek Mauro <dmauro@google.com>:

Add visibility restrictions to some internal targets

PiperOrigin-RevId: 400718253

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1de5061016bc42cd7be009c9725ed2343ce12e3d by Abseil Team <absl-team@google.com>:

Make it clear that operator<< can also be used in place of ToString when logging absl::Status.

PiperOrigin-RevId: 400248269

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cda15d9dc6e5cd569de7e5e73f409b72a3caed51 by Abseil Team <absl-team@google.com>:

Minor cleanup

PiperOrigin-RevId: 400087535

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b001375ec47da3a0434be9ca9a45c0df510e7dda by Abseil Team <absl-team@google.com>:

Move periodic_sampler from base/internal to profiling/internal

PiperOrigin-RevId: 400038533

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e7e02e686abc3900e723080849a3607d190ef57f by Abseil Team <absl-team@google.com>:

Move exponential_biased from base/internal to profiling/internal

PiperOrigin-RevId: 400020329
GitOrigin-RevId: 17141711ee419daa597a9f31e73721f80143e55a
Change-Id: I10924df7e1cc198447813dbe97a374a5cef66b49

1 files changed, 28 insertions, 27 deletions

diff --git a/absl/synchronization/mutex_test.cc b/absl/synchronization/mutex_test.cc
index f8fbf948..4f403176 100644
--- a/absl/synchronization/mutex_test.cc
+++ b/absl/synchronization/mutex_test.cc
@@ -26,6 +26,7 @@
 #include <random>
 #include <string>
 #include <thread>  // NOLINT(build/c++11)
+#include <type_traits>
 #include <vector>
 
 #include "gtest/gtest.h"
@@ -870,33 +871,6 @@ TEST(Mutex, LockedMutexDestructionBug) ABSL_NO_THREAD_SAFETY_ANALYSIS {
   }
 }
 
-// --------------------------------------------------------
-// Test for bug with pattern of readers using a condvar.  The bug was that if a
-// reader went to sleep on a condition variable while one or more other readers
-// held the lock, but there were no waiters, the reader count (held in the
-// mutex word) would be lost.  (This is because Enqueue() had at one time
-// always placed the thread on the Mutex queue.  Later (CL 4075610), to
-// tolerate re-entry into Mutex from a Condition predicate, Enqueue() was
-// changed so that it could also place a thread on a condition-variable.  This
-// introduced the case where Enqueue() returned with an empty queue, and this
-// case was handled incorrectly in one place.)
-
-static void ReaderForReaderOnCondVar(absl::Mutex *mu, absl::CondVar *cv,
-                                     int *running) {
-  std::random_device dev;
-  std::mt19937 gen(dev());
-  std::uniform_int_distribution<int> random_millis(0, 15);
-  mu->ReaderLock();
-  while (*running == 3) {
-    absl::SleepFor(absl::Milliseconds(random_millis(gen)));
-    cv->WaitWithTimeout(mu, absl::Milliseconds(random_millis(gen)));
-  }
-  mu->ReaderUnlock();
-  mu->Lock();
-  (*running)--;
-  mu->Unlock();
-}
-
 struct True {
   template <class... Args>
   bool operator()(Args...) const {
@@ -945,6 +919,33 @@ TEST(Mutex, FunctorCondition) {
   }
 }
 
+// --------------------------------------------------------
+// Test for bug with pattern of readers using a condvar.  The bug was that if a
+// reader went to sleep on a condition variable while one or more other readers
+// held the lock, but there were no waiters, the reader count (held in the
+// mutex word) would be lost.  (This is because Enqueue() had at one time
+// always placed the thread on the Mutex queue.  Later (CL 4075610), to
+// tolerate re-entry into Mutex from a Condition predicate, Enqueue() was
+// changed so that it could also place a thread on a condition-variable.  This
+// introduced the case where Enqueue() returned with an empty queue, and this
+// case was handled incorrectly in one place.)
+
+static void ReaderForReaderOnCondVar(absl::Mutex *mu, absl::CondVar *cv,
+                                     int *running) {
+  std::random_device dev;
+  std::mt19937 gen(dev());
+  std::uniform_int_distribution<int> random_millis(0, 15);
+  mu->ReaderLock();
+  while (*running == 3) {
+    absl::SleepFor(absl::Milliseconds(random_millis(gen)));
+    cv->WaitWithTimeout(mu, absl::Milliseconds(random_millis(gen)));
+  }
+  mu->ReaderUnlock();
+  mu->Lock();
+  (*running)--;
+  mu->Unlock();
+}
+
 static bool IntIsZero(int *x) { return *x == 0; }
 
 // Test for reader waiting condition variable when there are other readers