about summary refs log tree commit diff
path: root/third_party/abseil_cpp/absl/base/internal/spinlock_wait.cc
diff options
context:
space:
mode:
Diffstat (limited to 'third_party/abseil_cpp/absl/base/internal/spinlock_wait.cc')
-rw-r--r--third_party/abseil_cpp/absl/base/internal/spinlock_wait.cc81
1 files changed, 0 insertions, 81 deletions
diff --git a/third_party/abseil_cpp/absl/base/internal/spinlock_wait.cc b/third_party/abseil_cpp/absl/base/internal/spinlock_wait.cc
deleted file mode 100644
index fa824be1c008..000000000000
--- a/third_party/abseil_cpp/absl/base/internal/spinlock_wait.cc
+++ /dev/null
@@ -1,81 +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.
-
-// The OS-specific header included below must provide two calls:
-// AbslInternalSpinLockDelay() and AbslInternalSpinLockWake().
-// See spinlock_wait.h for the specs.
-
-#include <atomic>
-#include <cstdint>
-
-#include "absl/base/internal/spinlock_wait.h"
-
-#if defined(_WIN32)
-#include "absl/base/internal/spinlock_win32.inc"
-#elif defined(__linux__)
-#include "absl/base/internal/spinlock_linux.inc"
-#elif defined(__akaros__)
-#include "absl/base/internal/spinlock_akaros.inc"
-#else
-#include "absl/base/internal/spinlock_posix.inc"
-#endif
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace base_internal {
-
-// See spinlock_wait.h for spec.
-uint32_t SpinLockWait(std::atomic<uint32_t> *w, int n,
-                      const SpinLockWaitTransition trans[],
-                      base_internal::SchedulingMode scheduling_mode) {
-  int loop = 0;
-  for (;;) {
-    uint32_t v = w->load(std::memory_order_acquire);
-    int i;
-    for (i = 0; i != n && v != trans[i].from; i++) {
-    }
-    if (i == n) {
-      SpinLockDelay(w, v, ++loop, scheduling_mode);  // no matching transition
-    } else if (trans[i].to == v ||                   // null transition
-               w->compare_exchange_strong(v, trans[i].to,
-                                          std::memory_order_acquire,
-                                          std::memory_order_relaxed)) {
-      if (trans[i].done) return v;
-    }
-  }
-}
-
-static std::atomic<uint64_t> delay_rand;
-
-// Return a suggested delay in nanoseconds for iteration number "loop"
-int SpinLockSuggestedDelayNS(int loop) {
-  // Weak pseudo-random number generator to get some spread between threads
-  // when many are spinning.
-  uint64_t r = delay_rand.load(std::memory_order_relaxed);
-  r = 0x5deece66dLL * r + 0xb;   // numbers from nrand48()
-  delay_rand.store(r, std::memory_order_relaxed);
-
-  if (loop < 0 || loop > 32) {   // limit loop to 0..32
-    loop = 32;
-  }
-  const int kMinDelay = 128 << 10;  // 128us
-  // Double delay every 8 iterations, up to 16x (2ms).
-  int delay = kMinDelay << (loop / 8);
-  // Randomize in delay..2*delay range, for resulting 128us..4ms range.
-  return delay | ((delay - 1) & static_cast<int>(r));
-}
-
-}  // namespace base_internal
-ABSL_NAMESPACE_END
-}  // namespace absl