summaryrefslogtreecommitdiff
path: root/src/mongo/util/concurrency/threadlocal.h
blob: d6190bffb0f831337ecaf59aa39a87e67a70e2ae (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
#pragma once

/**
*    Copyright (C) 2011 10gen 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 <boost/thread/tss.hpp>

#include "mongo/config.h"

#include "mongo/base/disallow_copying.h"

#if defined(MONGO_CONFIG_HAVE_THREAD_LOCAL)
#define MONGO_TRIVIALLY_CONSTRUCTIBLE_THREAD_LOCAL thread_local
#elif defined(MONGO_CONFIG_HAVE___THREAD)
#define MONGO_TRIVIALLY_CONSTRUCTIBLE_THREAD_LOCAL __thread
#elif defined(MONGO_CONFIG_HAVE___DECLSPEC_THREAD)
#define MONGO_TRIVIALLY_CONSTRUCTIBLE_THREAD_LOCAL __declspec(thread)
#else
#error "Compiler must support trivially constructible thread local variables"
#endif

namespace mongo {

using boost::thread_specific_ptr;

/**
 * DEPRECATED, DO NOT USE.
 *
 * thread local "value" rather than a pointer
 * good for things which have copy constructors (and the copy constructor is fast enough)
 * e.g.
 *   ThreadLocalValue<int> myint;
 */
template <class T>
class ThreadLocalValue {
public:
    ThreadLocalValue(T def = 0) : _default(def) {}

    T get() const {
        T* val = _val.get();
        if (val)
            return *val;
        return _default;
    }

    void set(const T& i) {
        T* v = _val.get();
        if (v) {
            *v = i;
            return;
        }
        v = new T(i);
        _val.reset(v);
    }

    T& getRef() {
        T* v = _val.get();
        if (v) {
            return *v;
        }
        v = new T(_default);
        _val.reset(v);
        return *v;
    }

private:
    boost::thread_specific_ptr<T> _val;
    const T _default;
};

/**
 * Emulation of a thread local storage specifier used because not all supported
 * compiler toolchains support the C++11 thread_local storage class keyword.
 *
 * Since all supported toolchains do support a thread local storage class for
 * types that are trivially constructible and destructible, we perform the
 * emulation using that storage type and the machinery of boost::thread_specific_ptr to
 * handle deleting the objects on thread termination.
 */
template <class T>
class TSP {
    MONGO_DISALLOW_COPYING(TSP);

public:
    TSP() = default;
    T* get() const;
    void reset(T* v);
    T* getMake() {
        T* t = get();
        if (t == nullptr)
            reset(t = new T());
        return t;
    }

private:
    boost::thread_specific_ptr<T> tsp;
};

#define TSP_DECLARE(T, p) extern TSP<T> p;

#define TSP_DEFINE(T, p)                                \
    MONGO_TRIVIALLY_CONSTRUCTIBLE_THREAD_LOCAL T* _##p; \
    TSP<T> p;                                           \
    template <>                                         \
    T* TSP<T>::get() const {                            \
        return _##p;                                    \
    }                                                   \
    template <>                                         \
    void TSP<T>::reset(T* v) {                          \
        tsp.reset(v);                                   \
        _##p = v;                                       \
    }
}  // namespace mongo