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// Copyright 2018 Google LLC
//
// Licensed 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.
// Low level raw interfaces to the sequence counter used by the VDSO.
#ifndef VDSO_SEQLOCK_H_
#define VDSO_SEQLOCK_H_
#include <stdint.h>
#include "vdso/barrier.h"
#include "vdso/compiler.h"
namespace vdso {
inline int32_t read_seqcount_begin(const uint64_t* s) {
uint64_t seq = *s;
read_barrier();
return seq & ~1;
}
inline int read_seqcount_retry(const uint64_t* s, uint64_t seq) {
read_barrier();
return unlikely(*s != seq);
}
} // namespace vdso
#endif // VDSO_SEQLOCK_H_
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