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/**
* Copyright (C) 2014 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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/db/query/query_yield.h"
#include "mongo/db/curop.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/storage/record_fetcher.h"
namespace mongo {
// static
void QueryYield::yieldAllLocks(OperationContext* txn, RecordFetcher* fetcher) {
// Things have to happen here in a specific order:
// 1) Tell the RecordFetcher to do any setup which needs to happen inside locks
// 2) Release lock mgr locks
// 3) Go to sleep
// 4) Touch the record we're yielding on, if there is one (RecordFetcher::fetch)
// 5) Reacquire lock mgr locks
Locker* locker = txn->lockState();
Locker::LockSnapshot snapshot;
if (fetcher) {
fetcher->setup();
}
// Nothing was unlocked, just return, yielding is pointless.
if (!locker->saveLockStateAndUnlock(&snapshot)) {
return;
}
// Top-level locks are freed, release any potential low-level (storage engine-specific
// locks). If we are yielding, we are at a safe place to do so.
txn->recoveryUnit()->abandonSnapshot();
// Track the number of yields in CurOp.
CurOp::get(txn)->yielded();
if (fetcher) {
fetcher->fetch();
}
locker->restoreLockState(snapshot);
}
} // namespace mongo
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