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 #ifndef _LIBCPP_HAS_NO_THREADS 16 17 # include <__chrono/duration.h> 18 # include <__threading_support> 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_INLINE_VISIBILITY 28 bool operator()(chrono::nanoseconds __elapsed) const 29 { 30 if(__elapsed > chrono::milliseconds(128)) 31 __libcpp_thread_sleep_for(chrono::milliseconds(8)); 32 else if(__elapsed > chrono::microseconds(64)) 33 __libcpp_thread_sleep_for(__elapsed / 2); 34 else if(__elapsed > chrono::microseconds(4)) 35 __libcpp_thread_yield(); 36 else 37 {} // poll 38 return false; 39 } 40 }; 41 42 _LIBCPP_END_NAMESPACE_STD 43 44 #endif // _LIBCPP_HAS_NO_THREADS 45 46 #endif // _LIBCPP___THREAD_TIMED_BACKOFF_POLICY_H 47