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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/platform/basic.h"
#include "mongo/config.h"
#if !(defined(_WIN32) || MONGO_CONFIG_DEBUG_BUILD)
#include <sched.h>
#include <time.h>
#include "mongo/platform/pause.h"
#include "mongo/util/concurrency/spin_lock.h"
namespace mongo {
void SpinLock::_lockSlowPath() {
/**
* this is designed to perform close to the default spin lock
* the reason for the mild insanity is to prevent horrible performance
* when contention spikes
* it allows spinlocks to be used in many more places
* which is good because even with this change they are about 8x faster on linux
*/
for (int i = 0; i < 1000; i++) {
if (_tryLock())
return;
MONGO_YIELD_CORE_FOR_SMT();
}
for (int i = 0; i < 1000; i++) {
if (_tryLock())
return;
sched_yield();
}
struct timespec t;
t.tv_sec = 0;
t.tv_nsec = 5000000;
while (!_tryLock()) {
nanosleep(&t, NULL);
}
}
} // namespace mongo
#endif
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