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/*
* Copyright (C) 2018 The Android Open Source Project
*
* 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.
*/
#include "membarrier.h"
#include <errno.h>
#include <stdio.h>
#if !defined(_WIN32)
#include <sys/syscall.h>
#include <unistd.h>
#endif
#include "macros.h"
#include "utils.h"
#if __has_include(<linux/membarrier.h>)
#include <linux/membarrier.h>
#define CHECK_MEMBARRIER_CMD(art_value, membarrier_value) \
static_assert(static_cast<int>(art_value) == (membarrier_value), "Bad value for " # art_value)
CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kQuery, MEMBARRIER_CMD_QUERY);
CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kGlobal, MEMBARRIER_CMD_SHARED);
CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kPrivateExpedited, MEMBARRIER_CMD_PRIVATE_EXPEDITED);
CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kRegisterPrivateExpedited,
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED);
CHECK_MEMBARRIER_CMD(art::MembarrierCommand::kPrivateExpedited, MEMBARRIER_CMD_PRIVATE_EXPEDITED);
#undef CHECK_MEMBARRIER_CMD
#endif // __has_include(<linux/membarrier.h>)
namespace art {
#if defined(__linux__)
static bool IsMemBarrierSupported() {
// Check kernel version supports membarrier(2).
// MEMBARRIER_CMD_QUERY is supported since Linux 4.3.
// MEMBARRIER_CMD_PRIVATE_EXPEDITED is supported since Linux 4.14.
// MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE is supported since Linux 4.16.
// Lowest Linux version useful for ART is 4.14.
return IsKernelVersionAtLeast(4, 14);
}
int membarrier(MembarrierCommand command) {
static const bool membarrier_supported = IsMemBarrierSupported();
if (UNLIKELY(!membarrier_supported)) {
errno = ENOSYS;
return -1;
}
return syscall(__NR_membarrier, static_cast<int>(command), 0);
}
#else // __linux__
int membarrier([[maybe_unused]] MembarrierCommand command) {
errno = ENOSYS;
return -1;
}
#endif // __linux__
} // namespace art
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