40 lines
1.1 KiB
C++
40 lines
1.1 KiB
C++
// Copyright 2018 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// 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, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Low level raw interfaces to the sequence counter used by the VDSO.
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#ifndef VDSO_SEQLOCK_H_
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#define VDSO_SEQLOCK_H_
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#include <stdint.h>
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#include "vdso/barrier.h"
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#include "vdso/compiler.h"
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namespace vdso {
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inline int32_t read_seqcount_begin(const uint64_t* s) {
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uint64_t seq = *s;
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read_barrier();
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return seq & ~1;
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}
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inline int read_seqcount_retry(const uint64_t* s, uint64_t seq) {
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read_barrier();
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return unlikely(*s != seq);
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}
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} // namespace vdso
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#endif // VDSO_SEQLOCK_H_
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