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/**
* Copyright (C) 2022-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/db/transaction_participant_resource_yielder.h"
#include "mongo/db/session_catalog.h"
#include "mongo/db/session_catalog_mongod.h"
#include "mongo/db/transaction_participant.h"
namespace mongo {
std::unique_ptr<TransactionParticipantResourceYielder> TransactionParticipantResourceYielder::make(
StringData cmdName) {
return std::make_unique<TransactionParticipantResourceYielder>(cmdName);
}
void TransactionParticipantResourceYielder::yield(OperationContext* opCtx) {
// We're about to block. Check back in the session so that it's available to other threads. Note
// that we may block on a request to _ourselves_, meaning that we may have to wait for another
// thread which will use the same session. This step is necessary to prevent deadlocks.
Session* const session = OperationContextSession::get(opCtx);
if (session) {
if (auto txnParticipant = TransactionParticipant::get(opCtx)) {
txnParticipant.stashTransactionResources(opCtx);
}
MongoDOperationContextSession::checkIn(opCtx,
OperationContextSession::CheckInReason::kYield);
}
_yielded = (session != nullptr);
}
void TransactionParticipantResourceYielder::unyield(OperationContext* opCtx) {
if (_yielded) {
// This may block on a sub-operation on this node finishing. It's possible that while
// blocked on the network layer, another shard could have responded, theoretically
// unblocking this thread of execution. However, we must wait until the child operation on
// this shard finishes so we can get the session back. This may limit the throughput of the
// operation, but it's correct.
MongoDOperationContextSession::checkOut(opCtx);
if (auto txnParticipant = TransactionParticipant::get(opCtx)) {
txnParticipant.unstashTransactionResources(opCtx, _cmdName);
}
}
}
} // namespace mongo
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