57 lines
2.3 KiB
C
57 lines
2.3 KiB
C
// Licensed to the Apache Software Foundation (ASF) under one
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// or more contributor license agreements. See the NOTICE file
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// distributed with this work for additional information
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// regarding copyright ownership. The ASF licenses this file
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// to you under the Apache License, Version 2.0 (the
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// "License"); you may not use this file except in compliance
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// with the License. You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing,
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// software distributed under the License is distributed on an
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// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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// KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations
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// under the License.
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// bthread - A M:N threading library to make applications more concurrent.
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// Date: Fri Dec 5 13:40:57 CST 2014
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#ifndef BTHREAD_PROCESSOR_H
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#define BTHREAD_PROCESSOR_H
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#include "butil/build_config.h"
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// Pause instruction to prevent excess processor bus usage, only works in GCC
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# ifndef cpu_relax
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#if defined(ARCH_CPU_ARM_FAMILY)
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# define cpu_relax() asm volatile("yield\n": : :"memory")
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#else
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# define cpu_relax() asm volatile("pause\n": : :"memory")
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#endif
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# endif
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// Compile read-write barrier
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# ifndef barrier
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# define barrier() asm volatile("": : :"memory")
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# endif
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# define BT_LOOP_WHEN(expr, num_spins) \
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do { \
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/*sched_yield may change errno*/ \
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const int saved_errno = errno; \
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for (int cnt = 0, saved_nspin = (num_spins); (expr); ++cnt) { \
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if (cnt < saved_nspin) { \
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cpu_relax(); \
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} else { \
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sched_yield(); \
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} \
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} \
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errno = saved_errno; \
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} while (0)
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#endif // BTHREAD_PROCESSOR_H
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