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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you 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
//
// http://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.
// bthread - A M:N threading library to make applications more concurrent.
// Date: Fri Dec 5 13:40:57 CST 2014
#ifndef BTHREAD_PROCESSOR_H
#define BTHREAD_PROCESSOR_H
#include "butil/build_config.h"
// Pause instruction to prevent excess processor bus usage, only works in GCC
# ifndef cpu_relax
#if defined(ARCH_CPU_ARM_FAMILY)
# define cpu_relax() asm volatile("yield\n": : :"memory")
#else
# define cpu_relax() asm volatile("pause\n": : :"memory")
#endif
# endif
// Compile read-write barrier
# ifndef barrier
# define barrier() asm volatile("": : :"memory")
# endif
# define BT_LOOP_WHEN(expr, num_spins) \
do { \
/*sched_yield may change errno*/ \
const int saved_errno = errno; \
for (int cnt = 0, saved_nspin = (num_spins); (expr); ++cnt) { \
if (cnt < saved_nspin) { \
cpu_relax(); \
} else { \
sched_yield(); \
} \
} \
errno = saved_errno; \
} while (0)
#endif // BTHREAD_PROCESSOR_H