Export of internal Abseil changes

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

Import of CCTZ from GitHub.

PiperOrigin-RevId: 401384949

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

Internal change

PiperOrigin-RevId: 401337785

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

Internal change

PiperOrigin-RevId: 401047691

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

Note that SpinLock does not guarantee priorities for wakeups.

PiperOrigin-RevId: 400999238

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

Add visibility restrictions to some internal targets

PiperOrigin-RevId: 400718253

--
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

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

Minor cleanup

PiperOrigin-RevId: 400087535

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

Move periodic_sampler from base/internal to profiling/internal

PiperOrigin-RevId: 400038533

--
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

CMake/AbseilDll.cmake

@@ -17,8 +17,6 @@ set(ABSL_INTERNAL_DLL_FILES
   "base/internal/dynamic_annotations.h"
   "base/internal/endian.h"
   "base/internal/errno_saver.h"
-  "base/internal/exponential_biased.cc"
-  "base/internal/exponential_biased.h"
   "base/internal/fast_type_id.h"
   "base/internal/hide_ptr.h"
   "base/internal/identity.h"
@@ -28,8 +26,6 @@ set(ABSL_INTERNAL_DLL_FILES
   "base/internal/low_level_alloc.h"
   "base/internal/low_level_scheduling.h"
   "base/internal/per_thread_tls.h"
-  "base/internal/periodic_sampler.cc"
-  "base/internal/periodic_sampler.h"
   "base/internal/pretty_function.h"
   "base/internal/raw_logging.cc"
   "base/internal/raw_logging.h"
@@ -133,6 +129,10 @@ set(ABSL_INTERNAL_DLL_FILES
   "numeric/int128.h"
   "numeric/internal/bits.h"
   "numeric/internal/representation.h"
+  "profiling/internal/exponential_biased.cc"
+  "profiling/internal/exponential_biased.h"
+  "profiling/internal/periodic_sampler.cc"
+  "profiling/internal/periodic_sampler.h"
   "profiling/internal/sample_recorder.h"
   "random/bernoulli_distribution.h"
   "random/beta_distribution.h"

absl/base/BUILD.bazel

@@ -593,75 +593,6 @@ cc_test(
     ],
 )
 
-cc_library(
-    name = "exponential_biased",
-    srcs = ["internal/exponential_biased.cc"],
-    hdrs = ["internal/exponential_biased.h"],
-    linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = [
-        "//absl:__subpackages__",
-    ],
-    deps = [
-        ":config",
-        ":core_headers",
-    ],
-)
-
-cc_test(
-    name = "exponential_biased_test",
-    size = "small",
-    srcs = ["internal/exponential_biased_test.cc"],
-    copts = ABSL_TEST_COPTS,
-    linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = ["//visibility:private"],
-    deps = [
-        ":exponential_biased",
-        "//absl/strings",
-        "@com_google_googletest//:gtest_main",
-    ],
-)
-
-cc_library(
-    name = "periodic_sampler",
-    srcs = ["internal/periodic_sampler.cc"],
-    hdrs = ["internal/periodic_sampler.h"],
-    copts = ABSL_DEFAULT_COPTS,
-    linkopts = ABSL_DEFAULT_LINKOPTS,
-    deps = [
-        ":core_headers",
-        ":exponential_biased",
-    ],
-)
-
-cc_test(
-    name = "periodic_sampler_test",
-    size = "small",
-    srcs = ["internal/periodic_sampler_test.cc"],
-    copts = ABSL_TEST_COPTS,
-    linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = ["//visibility:private"],
-    deps = [
-        ":core_headers",
-        ":periodic_sampler",
-        "@com_google_googletest//:gtest_main",
-    ],
-)
-
-cc_binary(
-    name = "periodic_sampler_benchmark",
-    testonly = 1,
-    srcs = ["internal/periodic_sampler_benchmark.cc"],
-    copts = ABSL_TEST_COPTS,
-    linkopts = ABSL_DEFAULT_LINKOPTS,
-    tags = ["benchmark"],
-    visibility = ["//visibility:private"],
-    deps = [
-        ":core_headers",
-        ":periodic_sampler",
-        "@com_github_google_benchmark//:benchmark_main",
-    ],
-)
-
 cc_library(
     name = "scoped_set_env",
     testonly = 1,

absl/base/CMakeLists.txt

@@ -519,60 +519,6 @@ absl_cc_test(
     GTest::gtest_main
 )
 
-absl_cc_library(
-  NAME
-    exponential_biased
-  SRCS
-    "internal/exponential_biased.cc"
-  HDRS
-    "internal/exponential_biased.h"
-  COPTS
-    ${ABSL_DEFAULT_COPTS}
-  DEPS
-    absl::config
-    absl::core_headers
-)
-
-absl_cc_test(
-  NAME
-    exponential_biased_test
-  SRCS
-    "internal/exponential_biased_test.cc"
-  COPTS
-    ${ABSL_TEST_COPTS}
-  DEPS
-    absl::exponential_biased
-    absl::strings
-    GTest::gmock_main
-)
-
-absl_cc_library(
-  NAME
-    periodic_sampler
-  SRCS
-    "internal/periodic_sampler.cc"
-  HDRS
-    "internal/periodic_sampler.h"
-  COPTS
-    ${ABSL_DEFAULT_COPTS}
-  DEPS
-    absl::core_headers
-    absl::exponential_biased
-)
-
-absl_cc_test(
-  NAME
-    periodic_sampler_test
-  SRCS
-    "internal/periodic_sampler_test.cc"
-  COPTS
-    ${ABSL_TEST_COPTS}
-  DEPS
-    absl::core_headers
-    absl::periodic_sampler
-    GTest::gmock_main
-)
-
 absl_cc_library(
   NAME
     scoped_set_env

absl/base/internal/spinlock.h

@@ -16,13 +16,15 @@
 
 //  Most users requiring mutual exclusion should use Mutex.
 //  SpinLock is provided for use in two situations:
-//   - for use in code that Mutex itself depends on
+//   - for use by Abseil internal code that Mutex itself depends on
 //   - for async signal safety (see below)
 
 // SpinLock is async signal safe.  If a spinlock is used within a signal
 // handler, all code that acquires the lock must ensure that the signal cannot
 // arrive while they are holding the lock.  Typically, this is done by blocking
 // the signal.
+//
+// Threads waiting on a SpinLock may be woken in an arbitrary order.
 
 #ifndef ABSL_BASE_INTERNAL_SPINLOCK_H_
 #define ABSL_BASE_INTERNAL_SPINLOCK_H_

absl/base/internal/spinlock_wait.h

@@ -39,6 +39,8 @@ struct SpinLockWaitTransition {
 // satisfying 0<=i<n && trans[i].done, atomically make the transition,
 // then return the old value of *w.   Make any other atomic transitions
 // where !trans[i].done, but continue waiting.
+//
+// Wakeups for threads blocked on SpinLockWait do not respect priorities.
 uint32_t SpinLockWait(std::atomic<uint32_t> *w, int n,
                       const SpinLockWaitTransition trans[],
                       SchedulingMode scheduling_mode);

absl/container/BUILD.bazel

@@ -510,9 +510,9 @@ cc_library(
         ":have_sse",
         "//absl/base",
         "//absl/base:core_headers",
-        "//absl/base:exponential_biased",
         "//absl/debugging:stacktrace",
         "//absl/memory",
+        "//absl/profiling:exponential_biased",
         "//absl/profiling:sample_recorder",
         "//absl/synchronization",
         "//absl/utility",

absl/container/internal/hashtablez_sampler.cc

@@ -21,10 +21,10 @@
 #include <limits>
 
 #include "absl/base/attributes.h"
-#include "absl/base/internal/exponential_biased.h"
 #include "absl/container/internal/have_sse.h"
 #include "absl/debugging/stacktrace.h"
 #include "absl/memory/memory.h"
+#include "absl/profiling/internal/exponential_biased.h"
 #include "absl/profiling/internal/sample_recorder.h"
 #include "absl/synchronization/mutex.h"
 
@@ -40,7 +40,7 @@ ABSL_CONST_INIT std::atomic<bool> g_hashtablez_enabled{
 ABSL_CONST_INIT std::atomic<int32_t> g_hashtablez_sample_parameter{1 << 10};
 
 #if defined(ABSL_INTERNAL_HASHTABLEZ_SAMPLE)
-ABSL_PER_THREAD_TLS_KEYWORD absl::base_internal::ExponentialBiased
+ABSL_PER_THREAD_TLS_KEYWORD absl::profiling_internal::ExponentialBiased
     g_exponential_biased_generator;
 #endif
 

absl/debugging/BUILD.bazel

@@ -183,6 +183,7 @@ cc_library(
     ],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
     deps = [
         "//absl/base:config",
         "//absl/base:core_headers",
@@ -197,6 +198,7 @@ cc_library(
     srcs = ["internal/demangle.cc"],
     hdrs = ["internal/demangle.h"],
     copts = ABSL_DEFAULT_COPTS,
+    visibility = ["//visibility:private"],
     deps = [
         "//absl/base",
         "//absl/base:config",

absl/profiling/BUILD.bazel

@@ -16,6 +16,7 @@ load(
     "//absl:copts/configure_copts.bzl",
     "ABSL_DEFAULT_COPTS",
     "ABSL_DEFAULT_LINKOPTS",
+    "ABSL_TEST_COPTS",
 )
 
 package(default_visibility = ["//visibility:private"])
@@ -51,3 +52,75 @@ cc_test(
         "@com_google_googletest//:gtest_main",
     ],
 )
+
+cc_library(
+    name = "exponential_biased",
+    srcs = ["internal/exponential_biased.cc"],
+    hdrs = ["internal/exponential_biased.h"],
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = [
+        "//absl:__subpackages__",
+    ],
+    deps = [
+        "//absl/base:config",
+        "//absl/base:core_headers",
+    ],
+)
+
+cc_test(
+    name = "exponential_biased_test",
+    size = "small",
+    srcs = ["internal/exponential_biased_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":exponential_biased",
+        "//absl/strings",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_library(
+    name = "periodic_sampler",
+    srcs = ["internal/periodic_sampler.cc"],
+    hdrs = ["internal/periodic_sampler.h"],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = [
+        "//absl:__subpackages__",
+    ],
+    deps = [
+        ":exponential_biased",
+        "//absl/base:core_headers",
+    ],
+)
+
+cc_test(
+    name = "periodic_sampler_test",
+    size = "small",
+    srcs = ["internal/periodic_sampler_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":periodic_sampler",
+        "//absl/base:core_headers",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_binary(
+    name = "periodic_sampler_benchmark",
+    testonly = 1,
+    srcs = ["internal/periodic_sampler_benchmark.cc"],
+    copts = ABSL_TEST_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    tags = ["benchmark"],
+    visibility = ["//visibility:private"],
+    deps = [
+        ":periodic_sampler",
+        "//absl/base:core_headers",
+        "@com_github_google_benchmark//:benchmark_main",
+    ],
+)

absl/profiling/CMakeLists.txt

@@ -37,3 +37,57 @@ absl_cc_test(
     GTest::gmock_main
 )
 
+absl_cc_library(
+  NAME
+    exponential_biased
+  SRCS
+    "internal/exponential_biased.cc"
+  HDRS
+    "internal/exponential_biased.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::config
+    absl::core_headers
+)
+
+absl_cc_test(
+  NAME
+    exponential_biased_test
+  SRCS
+    "internal/exponential_biased_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::exponential_biased
+    absl::strings
+    GTest::gmock_main
+)
+
+absl_cc_library(
+  NAME
+    periodic_sampler
+  SRCS
+    "internal/periodic_sampler.cc"
+  HDRS
+    "internal/periodic_sampler.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::core_headers
+    absl::exponential_biased
+)
+
+absl_cc_test(
+  NAME
+    periodic_sampler_test
+  SRCS
+    "internal/periodic_sampler_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::core_headers
+    absl::periodic_sampler
+    GTest::gmock_main
+)
+

absl/profiling/internal/exponential_biased.cc

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "absl/base/internal/exponential_biased.h"
+#include "absl/profiling/internal/exponential_biased.h"
 
 #include <stdint.h>
 
@@ -26,7 +26,7 @@
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
-namespace base_internal {
+namespace profiling_internal {
 
 // The algorithm generates a random number between 0 and 1 and applies the
 // inverse cumulative distribution function for an exponential. Specifically:
@@ -88,6 +88,6 @@ void ExponentialBiased::Initialize() {
   initialized_ = true;
 }
 
-}  // namespace base_internal
+}  // namespace profiling_internal
 ABSL_NAMESPACE_END
 }  // namespace absl

absl/profiling/internal/exponential_biased.h

@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#ifndef ABSL_BASE_INTERNAL_EXPONENTIAL_BIASED_H_
-#define ABSL_BASE_INTERNAL_EXPONENTIAL_BIASED_H_
+#ifndef ABSL_PROFILING_INTERNAL_EXPONENTIAL_BIASED_H_
+#define ABSL_PROFILING_INTERNAL_EXPONENTIAL_BIASED_H_
 
 #include <stdint.h>
 
@@ -22,7 +22,7 @@
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
-namespace base_internal {
+namespace profiling_internal {
 
 // ExponentialBiased provides a small and fast random number generator for a
 // rounded exponential distribution. This generator manages very little state,
@@ -123,8 +123,8 @@ inline uint64_t ExponentialBiased::NextRandom(uint64_t rnd) {
   return (prng_mult * rnd + prng_add) & prng_mod_mask;
 }
 
-}  // namespace base_internal
+}  // namespace profiling_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
 
-#endif  // ABSL_BASE_INTERNAL_EXPONENTIAL_BIASED_H_
+#endif  // ABSL_PROFILING_INTERNAL_EXPONENTIAL_BIASED_H_

absl/profiling/internal/exponential_biased_test.cc

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "absl/base/internal/exponential_biased.h"
+#include "absl/profiling/internal/exponential_biased.h"
 
 #include <stddef.h>
 
@@ -28,7 +28,7 @@ using ::testing::Ge;
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
-namespace base_internal {
+namespace profiling_internal {
 
 MATCHER_P2(IsBetween, a, b,
            absl::StrCat(std::string(negation ? "isn't" : "is"), " between ", a,
@@ -194,6 +194,6 @@ TEST(ExponentialBiasedTest, InitializationModes) {
   EXPECT_THAT(eb_stack.GetSkipCount(2), Ge(0));
 }
 
-}  // namespace base_internal
+}  // namespace profiling_internal
 ABSL_NAMESPACE_END
 }  // namespace absl

absl/profiling/internal/periodic_sampler.cc

@@ -12,15 +12,15 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "absl/base/internal/periodic_sampler.h"
+#include "absl/profiling/internal/periodic_sampler.h"
 
 #include <atomic>
 
-#include "absl/base/internal/exponential_biased.h"
+#include "absl/profiling/internal/exponential_biased.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
-namespace base_internal {
+namespace profiling_internal {
 
 int64_t PeriodicSamplerBase::GetExponentialBiased(int period) noexcept {
   return rng_.GetStride(period);
@@ -48,6 +48,6 @@ bool PeriodicSamplerBase::SubtleConfirmSample() noexcept {
   return true;
 }
 
-}  // namespace base_internal
+}  // namespace profiling_internal
 ABSL_NAMESPACE_END
 }  // namespace absl

absl/profiling/internal/periodic_sampler.h

@@ -12,19 +12,19 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#ifndef ABSL_BASE_INTERNAL_PERIODIC_SAMPLER_H_
-#define ABSL_BASE_INTERNAL_PERIODIC_SAMPLER_H_
+#ifndef ABSL_PROFILING_INTERNAL_PERIODIC_SAMPLER_H_
+#define ABSL_PROFILING_INTERNAL_PERIODIC_SAMPLER_H_
 
 #include <stdint.h>
 
 #include <atomic>
 
-#include "absl/base/internal/exponential_biased.h"
 #include "absl/base/optimization.h"
+#include "absl/profiling/internal/exponential_biased.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
-namespace base_internal {
+namespace profiling_internal {
 
 // PeriodicSamplerBase provides the basic period sampler implementation.
 //
@@ -149,7 +149,7 @@ class PeriodicSamplerBase {
   //   ICC   x64 (OK) : https://gcc.godbolt.org/z/ptTNfD
   //   MSVC  x64 (OK) : https://gcc.godbolt.org/z/76j4-5
   uint64_t stride_ = 0;
-  ExponentialBiased rng_;
+  absl::profiling_internal::ExponentialBiased rng_;
 };
 
 inline bool PeriodicSamplerBase::SubtleMaybeSample() noexcept {
@@ -204,8 +204,8 @@ class PeriodicSampler final : public PeriodicSamplerBase {
 template <typename Tag, int default_period>
 std::atomic<int> PeriodicSampler<Tag, default_period>::period_(default_period);
 
-}  // namespace base_internal
+}  // namespace profiling_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
 
-#endif  // ABSL_BASE_INTERNAL_PERIODIC_SAMPLER_H_
+#endif  // ABSL_PROFILING_INTERNAL_PERIODIC_SAMPLER_H_

absl/profiling/internal/periodic_sampler_benchmark.cc

@@ -12,12 +12,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include "absl/profiling/internal/periodic_sampler.h"
 #include "benchmark/benchmark.h"
-#include "absl/base/internal/periodic_sampler.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
-namespace base_internal {
+namespace profiling_internal {
 namespace {
 
 template <typename Sampler>
@@ -74,6 +74,6 @@ void BM_PeriodicSampler_Disabled(benchmark::State& state) {
 BENCHMARK(BM_PeriodicSampler_Disabled);
 
 }  // namespace
-}  // namespace base_internal
+}  // namespace profiling_internal
 ABSL_NAMESPACE_END
 }  // namespace absl

absl/profiling/internal/periodic_sampler_test.cc

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "absl/base/internal/periodic_sampler.h"
+#include "absl/profiling/internal/periodic_sampler.h"
 
 #include <thread>  // NOLINT(build/c++11)
 
@@ -23,7 +23,7 @@
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
-namespace base_internal {
+namespace profiling_internal {
 namespace {
 
 using testing::Eq;
@@ -172,6 +172,6 @@ TEST(PeriodicSamplerTest, SetGlobalPeriod) {
 }
 
 }  // namespace
-}  // namespace base_internal
+}  // namespace profiling_internal
 ABSL_NAMESPACE_END
 }  // namespace absl

absl/status/status.h

@@ -494,7 +494,7 @@ class Status final {
   // Returns the error message associated with this error code, if available.
   // Note that this message rarely describes the error code.  It is not unusual
   // for the error message to be the empty string. As a result, prefer
-  // `Status::ToString()` for debug logging.
+  // `operator<<` or `Status::ToString()` for debug logging.
   absl::string_view message() const;
 
   friend bool operator==(const Status&, const Status&);

absl/strings/BUILD.bazel

@@ -508,8 +508,8 @@ cc_library(
     deps = [
         "//absl/base:config",
         "//absl/base:core_headers",
-        "//absl/base:exponential_biased",
         "//absl/base:raw_logging_internal",
+        "//absl/profiling:exponential_biased",
     ],
 )
 

absl/strings/internal/cordz_functions.cc

@@ -21,8 +21,8 @@
 
 #include "absl/base/attributes.h"
 #include "absl/base/config.h"
-#include "absl/base/internal/exponential_biased.h"
 #include "absl/base/internal/raw_logging.h"
+#include "absl/profiling/internal/exponential_biased.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -48,7 +48,7 @@ constexpr int64_t kIntervalIfDisabled = 1 << 16;
 
 ABSL_ATTRIBUTE_NOINLINE bool cordz_should_profile_slow() {
 
-  thread_local absl::base_internal::ExponentialBiased
+  thread_local absl::profiling_internal::ExponentialBiased
       exponential_biased_generator;
   int32_t mean_interval = get_cordz_mean_interval();
 

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

absl/time/internal/cctz/src/cctz_benchmark.cc

@@ -648,6 +648,7 @@ const char* const kTimeZoneNames[] = {"Africa/Abidjan",
                                       "Pacific/Guam",
                                       "Pacific/Honolulu",
                                       "Pacific/Johnston",
+                                      "Pacific/Kanton",
                                       "Pacific/Kiritimati",
                                       "Pacific/Kosrae",
                                       "Pacific/Kwajalein",

absl/time/internal/cctz/src/time_zone_lookup_test.cc

@@ -579,6 +579,7 @@ const char* const kTimeZoneNames[] = {"Africa/Abidjan",
                                       "Pacific/Guam",
                                       "Pacific/Honolulu",
                                       "Pacific/Johnston",
+                                      "Pacific/Kanton",
                                       "Pacific/Kiritimati",
                                       "Pacific/Kosrae",
                                       "Pacific/Kwajalein",

absl/time/internal/cctz/testdata/version

@@ -1 +1 @@
-2021b
+2021c