// Copyright 2018 The gVisor Authors. // // 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_