libcxx/include/__thread/timed_backoff_policy.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___THREAD_TIMED_BACKOFF_POLICY_H
  11 #define _LIBCPP___THREAD_TIMED_BACKOFF_POLICY_H
  12
  13 #include <__config>
  14
  15 #if _LIBCPP_HAS_THREADS
  16
  17 #  include <__chrono/duration.h>
  18 #  include <__thread/support.h>
  19
  20 #  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  21 #    pragma GCC system_header
  22 #  endif
  23
  24 _LIBCPP_BEGIN_NAMESPACE_STD
  25
  26 struct __libcpp_timed_backoff_policy {
  27   _LIBCPP_HIDE_FROM_ABI bool operator()(chrono::nanoseconds __elapsed) const {
  28     if (__elapsed > chrono::milliseconds(128))
  29       __libcpp_thread_sleep_for(chrono::milliseconds(8));
  30     else if (__elapsed > chrono::microseconds(64))
  31       __libcpp_thread_sleep_for(__elapsed / 2);
  32     else if (__elapsed > chrono::microseconds(4))
  33       __libcpp_thread_yield();
  34     else {
  35     } // poll
  36     return false;
  37   }
  38 };
  39
  40 _LIBCPP_END_NAMESPACE_STD
  41
  42 #endif // _LIBCPP_HAS_THREADS
  43
  44 #endif // _LIBCPP___THREAD_TIMED_BACKOFF_POLICY_H