Synchronization: Refactor Waiter to allow us to write tests

Instead of being only able to test the platform Waiter implementation,
this allows us to be able to test all Waiter implementations that
build on a specific platform.

A unittest is added that tests all implementations that work for the
platform, and allows us to check that the expected one is being used
by printing the name of the selected implementation.

PiperOrigin-RevId: 518072415
Change-Id: Ie9e6fcd9d8283b4038e6f4e68a304d2adcc04b19

1 files changed, 0 insertions, 400 deletions

diff --git a/absl/synchronization/internal/waiter.cc b/absl/synchronization/internal/waiter.cc
deleted file mode 100644
index 1b8d8d09..00000000
--- a/absl/synchronization/internal/waiter.cc
+++ /dev/null
@@ -1,400 +0,0 @@
-// Copyright 2017 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/synchronization/internal/waiter.h"
-
-#include "absl/base/config.h"
-
-#ifdef _WIN32
-#include <windows.h>
-#else
-#include <pthread.h>
-#include <sys/time.h>
-#include <unistd.h>
-#endif
-
-#ifdef __linux__
-#include <linux/futex.h>
-#include <sys/syscall.h>
-#endif
-
-#ifdef ABSL_HAVE_SEMAPHORE_H
-#include <semaphore.h>
-#endif
-
-#include <errno.h>
-#include <stdio.h>
-#include <time.h>
-
-#include <atomic>
-#include <cassert>
-#include <cstdint>
-#include <new>
-#include <type_traits>
-
-#include "absl/base/internal/raw_logging.h"
-#include "absl/base/internal/thread_identity.h"
-#include "absl/base/optimization.h"
-#include "absl/synchronization/internal/kernel_timeout.h"
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace synchronization_internal {
-
-static void MaybeBecomeIdle() {
-  base_internal::ThreadIdentity *identity =
-      base_internal::CurrentThreadIdentityIfPresent();
-  assert(identity != nullptr);
-  const bool is_idle = identity->is_idle.load(std::memory_order_relaxed);
-  const int ticker = identity->ticker.load(std::memory_order_relaxed);
-  const int wait_start = identity->wait_start.load(std::memory_order_relaxed);
-  if (!is_idle && ticker - wait_start > Waiter::kIdlePeriods) {
-    identity->is_idle.store(true, std::memory_order_relaxed);
-  }
-}
-
-#if ABSL_WAITER_MODE == ABSL_WAITER_MODE_FUTEX
-
-Waiter::Waiter() : futex_(0) {}
-
-bool Waiter::Wait(KernelTimeout t) {
-  // Loop until we can atomically decrement futex from a positive
-  // value, waiting on a futex while we believe it is zero.
-  // Note that, since the thread ticker is just reset, we don't need to check
-  // whether the thread is idle on the very first pass of the loop.
-  bool first_pass = true;
-
-  while (true) {
-    int32_t x = futex_.load(std::memory_order_relaxed);
-    while (x != 0) {
-      if (!futex_.compare_exchange_weak(x, x - 1,
-                                        std::memory_order_acquire,
-                                        std::memory_order_relaxed)) {
-        continue;  // Raced with someone, retry.
-      }
-      return true;  // Consumed a wakeup, we are done.
-    }
-
-    if (!first_pass) MaybeBecomeIdle();
-    const int err = Futex::WaitUntil(&futex_, 0, t);
-    if (err != 0) {
-      if (err == -EINTR || err == -EWOULDBLOCK) {
-        // Do nothing, the loop will retry.
-      } else if (err == -ETIMEDOUT) {
-        return false;
-      } else {
-        ABSL_RAW_LOG(FATAL, "Futex operation failed with error %d\n", err);
-      }
-    }
-    first_pass = false;
-  }
-}
-
-void Waiter::Post() {
-  if (futex_.fetch_add(1, std::memory_order_release) == 0) {
-    // We incremented from 0, need to wake a potential waiter.
-    Poke();
-  }
-}
-
-void Waiter::Poke() {
-  // Wake one thread waiting on the futex.
-  const int err = Futex::Wake(&futex_, 1);
-  if (ABSL_PREDICT_FALSE(err < 0)) {
-    ABSL_RAW_LOG(FATAL, "Futex operation failed with error %d\n", err);
-  }
-}
-
-#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_CONDVAR
-
-class PthreadMutexHolder {
- public:
-  explicit PthreadMutexHolder(pthread_mutex_t *mu) : mu_(mu) {
-    const int err = pthread_mutex_lock(mu_);
-    if (err != 0) {
-      ABSL_RAW_LOG(FATAL, "pthread_mutex_lock failed: %d", err);
-    }
-  }
-
-  PthreadMutexHolder(const PthreadMutexHolder &rhs) = delete;
-  PthreadMutexHolder &operator=(const PthreadMutexHolder &rhs) = delete;
-
-  ~PthreadMutexHolder() {
-    const int err = pthread_mutex_unlock(mu_);
-    if (err != 0) {
-      ABSL_RAW_LOG(FATAL, "pthread_mutex_unlock failed: %d", err);
-    }
-  }
-
- private:
-  pthread_mutex_t *mu_;
-};
-
-Waiter::Waiter() {
-  const int err = pthread_mutex_init(&mu_, 0);
-  if (err != 0) {
-    ABSL_RAW_LOG(FATAL, "pthread_mutex_init failed: %d", err);
-  }
-
-  const int err2 = pthread_cond_init(&cv_, 0);
-  if (err2 != 0) {
-    ABSL_RAW_LOG(FATAL, "pthread_cond_init failed: %d", err2);
-  }
-
-  waiter_count_ = 0;
-  wakeup_count_ = 0;
-}
-
-bool Waiter::Wait(KernelTimeout t) {
-  struct timespec abs_timeout;
-  if (t.has_timeout()) {
-    abs_timeout = t.MakeAbsTimespec();
-  }
-
-  PthreadMutexHolder h(&mu_);
-  ++waiter_count_;
-  // Loop until we find a wakeup to consume or timeout.
-  // Note that, since the thread ticker is just reset, we don't need to check
-  // whether the thread is idle on the very first pass of the loop.
-  bool first_pass = true;
-  while (wakeup_count_ == 0) {
-    if (!first_pass) MaybeBecomeIdle();
-    // No wakeups available, time to wait.
-    if (!t.has_timeout()) {
-      const int err = pthread_cond_wait(&cv_, &mu_);
-      if (err != 0) {
-        ABSL_RAW_LOG(FATAL, "pthread_cond_wait failed: %d", err);
-      }
-    } else {
-      const int err = pthread_cond_timedwait(&cv_, &mu_, &abs_timeout);
-      if (err == ETIMEDOUT) {
-        --waiter_count_;
-        return false;
-      }
-      if (err != 0) {
-        ABSL_RAW_LOG(FATAL, "pthread_cond_timedwait failed: %d", err);
-      }
-    }
-    first_pass = false;
-  }
-  // Consume a wakeup and we're done.
-  --wakeup_count_;
-  --waiter_count_;
-  return true;
-}
-
-void Waiter::Post() {
-  PthreadMutexHolder h(&mu_);
-  ++wakeup_count_;
-  InternalCondVarPoke();
-}
-
-void Waiter::Poke() {
-  PthreadMutexHolder h(&mu_);
-  InternalCondVarPoke();
-}
-
-void Waiter::InternalCondVarPoke() {
-  if (waiter_count_ != 0) {
-    const int err = pthread_cond_signal(&cv_);
-    if (ABSL_PREDICT_FALSE(err != 0)) {
-      ABSL_RAW_LOG(FATAL, "pthread_cond_signal failed: %d", err);
-    }
-  }
-}
-
-#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_SEM
-
-Waiter::Waiter() {
-  if (sem_init(&sem_, 0, 0) != 0) {
-    ABSL_RAW_LOG(FATAL, "sem_init failed with errno %d\n", errno);
-  }
-  wakeups_.store(0, std::memory_order_relaxed);
-}
-
-bool Waiter::Wait(KernelTimeout t) {
-  struct timespec abs_timeout;
-  if (t.has_timeout()) {
-    abs_timeout = t.MakeAbsTimespec();
-  }
-
-  // Loop until we timeout or consume a wakeup.
-  // Note that, since the thread ticker is just reset, we don't need to check
-  // whether the thread is idle on the very first pass of the loop.
-  bool first_pass = true;
-  while (true) {
-    int x = wakeups_.load(std::memory_order_relaxed);
-    while (x != 0) {
-      if (!wakeups_.compare_exchange_weak(x, x - 1,
-                                          std::memory_order_acquire,
-                                          std::memory_order_relaxed)) {
-        continue;  // Raced with someone, retry.
-      }
-      // Successfully consumed a wakeup, we're done.
-      return true;
-    }
-
-    if (!first_pass) MaybeBecomeIdle();
-    // Nothing to consume, wait (looping on EINTR).
-    while (true) {
-      if (!t.has_timeout()) {
-        if (sem_wait(&sem_) == 0) break;
-        if (errno == EINTR) continue;
-        ABSL_RAW_LOG(FATAL, "sem_wait failed: %d", errno);
-      } else {
-        if (sem_timedwait(&sem_, &abs_timeout) == 0) break;
-        if (errno == EINTR) continue;
-        if (errno == ETIMEDOUT) return false;
-        ABSL_RAW_LOG(FATAL, "sem_timedwait failed: %d", errno);
-      }
-    }
-    first_pass = false;
-  }
-}
-
-void Waiter::Post() {
-  // Post a wakeup.
-  if (wakeups_.fetch_add(1, std::memory_order_release) == 0) {
-    // We incremented from 0, need to wake a potential waiter.
-    Poke();
-  }
-}
-
-void Waiter::Poke() {
-  if (sem_post(&sem_) != 0) {  // Wake any semaphore waiter.
-    ABSL_RAW_LOG(FATAL, "sem_post failed with errno %d\n", errno);
-  }
-}
-
-#elif ABSL_WAITER_MODE == ABSL_WAITER_MODE_WIN32
-
-class Waiter::WinHelper {
- public:
-  static SRWLOCK *GetLock(Waiter *w) {
-    return reinterpret_cast<SRWLOCK *>(&w->mu_storage_);
-  }
-
-  static CONDITION_VARIABLE *GetCond(Waiter *w) {
-    return reinterpret_cast<CONDITION_VARIABLE *>(&w->cv_storage_);
-  }
-
-  static_assert(sizeof(SRWLOCK) == sizeof(void *),
-                "`mu_storage_` does not have the same size as SRWLOCK");
-  static_assert(alignof(SRWLOCK) == alignof(void *),
-                "`mu_storage_` does not have the same alignment as SRWLOCK");
-
-  static_assert(sizeof(CONDITION_VARIABLE) == sizeof(void *),
-                "`ABSL_CONDITION_VARIABLE_STORAGE` does not have the same size "
-                "as `CONDITION_VARIABLE`");
-  static_assert(
-      alignof(CONDITION_VARIABLE) == alignof(void *),
-      "`cv_storage_` does not have the same alignment as `CONDITION_VARIABLE`");
-
-  // The SRWLOCK and CONDITION_VARIABLE types must be trivially constructible
-  // and destructible because we never call their constructors or destructors.
-  static_assert(std::is_trivially_constructible<SRWLOCK>::value,
-                "The `SRWLOCK` type must be trivially constructible");
-  static_assert(
-      std::is_trivially_constructible<CONDITION_VARIABLE>::value,
-      "The `CONDITION_VARIABLE` type must be trivially constructible");
-  static_assert(std::is_trivially_destructible<SRWLOCK>::value,
-                "The `SRWLOCK` type must be trivially destructible");
-  static_assert(std::is_trivially_destructible<CONDITION_VARIABLE>::value,
-                "The `CONDITION_VARIABLE` type must be trivially destructible");
-};
-
-class LockHolder {
- public:
-  explicit LockHolder(SRWLOCK* mu) : mu_(mu) {
-    AcquireSRWLockExclusive(mu_);
-  }
-
-  LockHolder(const LockHolder&) = delete;
-  LockHolder& operator=(const LockHolder&) = delete;
-
-  ~LockHolder() {
-    ReleaseSRWLockExclusive(mu_);
-  }
-
- private:
-  SRWLOCK* mu_;
-};
-
-Waiter::Waiter() {
-  auto *mu = ::new (static_cast<void *>(&mu_storage_)) SRWLOCK;
-  auto *cv = ::new (static_cast<void *>(&cv_storage_)) CONDITION_VARIABLE;
-  InitializeSRWLock(mu);
-  InitializeConditionVariable(cv);
-  waiter_count_ = 0;
-  wakeup_count_ = 0;
-}
-
-bool Waiter::Wait(KernelTimeout t) {
-  SRWLOCK *mu = WinHelper::GetLock(this);
-  CONDITION_VARIABLE *cv = WinHelper::GetCond(this);
-
-  LockHolder h(mu);
-  ++waiter_count_;
-
-  // Loop until we find a wakeup to consume or timeout.
-  // Note that, since the thread ticker is just reset, we don't need to check
-  // whether the thread is idle on the very first pass of the loop.
-  bool first_pass = true;
-  while (wakeup_count_ == 0) {
-    if (!first_pass) MaybeBecomeIdle();
-    // No wakeups available, time to wait.
-    if (!SleepConditionVariableSRW(cv, mu, t.InMillisecondsFromNow(), 0)) {
-      // GetLastError() returns a Win32 DWORD, but we assign to
-      // unsigned long to simplify the ABSL_RAW_LOG case below.  The uniform
-      // initialization guarantees this is not a narrowing conversion.
-      const unsigned long err{GetLastError()};  // NOLINT(runtime/int)
-      if (err == ERROR_TIMEOUT) {
-        --waiter_count_;
-        return false;
-      } else {
-        ABSL_RAW_LOG(FATAL, "SleepConditionVariableSRW failed: %lu", err);
-      }
-    }
-    first_pass = false;
-  }
-  // Consume a wakeup and we're done.
-  --wakeup_count_;
-  --waiter_count_;
-  return true;
-}
-
-void Waiter::Post() {
-  LockHolder h(WinHelper::GetLock(this));
-  ++wakeup_count_;
-  InternalCondVarPoke();
-}
-
-void Waiter::Poke() {
-  LockHolder h(WinHelper::GetLock(this));
-  InternalCondVarPoke();
-}
-
-void Waiter::InternalCondVarPoke() {
-  if (waiter_count_ != 0) {
-    WakeConditionVariable(WinHelper::GetCond(this));
-  }
-}
-
-#else
-#error Unknown ABSL_WAITER_MODE
-#endif
-
-}  // namespace synchronization_internal
-ABSL_NAMESPACE_END
-}  // namespace absl