1 
2 /**
3  *    Copyright (C) 2018-present MongoDB, Inc.
4  *
5  *    This program is free software: you can redistribute it and/or modify
6  *    it under the terms of the Server Side Public License, version 1,
7  *    as published by MongoDB, Inc.
8  *
9  *    This program is distributed in the hope that it will be useful,
10  *    but WITHOUT ANY WARRANTY; without even the implied warranty of
11  *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  *    Server Side Public License for more details.
13  *
14  *    You should have received a copy of the Server Side Public License
15  *    along with this program. If not, see
16  *    <http://www.mongodb.com/licensing/server-side-public-license>.
17  *
18  *    As a special exception, the copyright holders give permission to link the
19  *    code of portions of this program with the OpenSSL library under certain
20  *    conditions as described in each individual source file and distribute
21  *    linked combinations including the program with the OpenSSL library. You
22  *    must comply with the Server Side Public License in all respects for
23  *    all of the code used other than as permitted herein. If you modify file(s)
24  *    with this exception, you may extend this exception to your version of the
25  *    file(s), but you are not obligated to do so. If you do not wish to do so,
26  *    delete this exception statement from your version. If you delete this
27  *    exception statement from all source files in the program, then also delete
28  *    it in the license file.
29  */
30 
31 #pragma once
32 
33 #include "mongo/db/namespace_string.h"
34 #include "mongo/stdx/functional.h"
35 
36 namespace mongo {
37 
38 class OperationContext;
39 class RecordFetcher;
40 
41 /**
42  * See the documentation for yieldAllLocks(...).
43  */
44 class QueryYield {
45     QueryYield();
46 
47 public:
48     /**
49      * If not in a nested context, unlocks all locks, suggests to the operating system to
50      * switch to another thread, and then reacquires all locks.
51      *
52      * If in a nested context (eg DBDirectClient), does nothing.
53      *
54      * The whileYieldingFn will be executed after unlocking the locks and before re-acquiring them.
55      */
56     static void yieldAllLocks(OperationContext* opCtx,
57                               stdx::function<void()> whileYieldingFn,
58                               const NamespaceString& planExecNS);
59 };
60 
61 }  // namespace mongo
62