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
26struct __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