aboutsummaryrefslogtreecommitdiffstats
path: root/library/cpp/yt/threading/at_fork.cpp
blob: 2046918fcbf7586048b3a50f97988dbde04cdc26 (plain) (blame)
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
139
#include "at_fork.h"

#include <library/cpp/yt/memory/leaky_singleton.h>

#include <library/cpp/yt/assert/assert.h>

#ifdef _unix_
    #include <pthread.h>
#endif

#include <atomic>
#include <array>

namespace NYT::NThreading {

////////////////////////////////////////////////////////////////////////////////

class TAtForkManager
{
public:
    static TAtForkManager* Get()
    {
        return LeakySingleton<TAtForkManager>();
    }

    void RegisterAtForkHandlers(
        TAtForkHandler prepare,
        TAtForkHandler parent,
        TAtForkHandler child)
    {
        int index = AtForkHandlerCount_++;
        Y_ABORT_UNLESS(index < MaxAtForkHandlerSets);
        auto& set = AtForkHandlerSets_[index];
        set.Prepare = std::move(prepare);
        set.Parent = std::move(parent);
        set.Child = std::move(child);
        set.Initialized.store(true);
    }

    TReaderWriterSpinLock* GetForkLock()
    {
        return &ForkLock_;
    }

private:
    DECLARE_LEAKY_SINGLETON_FRIEND()

    TReaderWriterSpinLock ForkLock_;

    struct TAtForkHandlerSet
    {
        TAtForkHandler Prepare;
        TAtForkHandler Parent;
        TAtForkHandler Child;
        std::atomic<bool> Initialized;
    };

    static constexpr int MaxAtForkHandlerSets = 8;
    std::array<TAtForkHandlerSet, MaxAtForkHandlerSets> AtForkHandlerSets_;
    std::atomic<int> AtForkHandlerCount_ = 0;

    TAtForkManager()
    {
#ifdef _unix_
        pthread_atfork(
            [] { Get()->OnPrepare(); },
            [] { Get()->OnParent(); },
            [] { Get()->OnChild(); });
#endif
    }

    void OnPrepare()
    {
        IterateAtForkHandlerSets([] (const TAtForkHandlerSet& set) {
            if (set.Prepare) {
                set.Prepare();
            }
        });
        ForkLock_.AcquireWriter();
    }


    void OnParent()
    {
        ForkLock_.ReleaseWriter();
        IterateAtForkHandlerSets([] (const TAtForkHandlerSet& set) {
            if (set.Parent) {
                set.Parent();
            }
        });
    }

    void OnChild()
    {
        ForkLock_.ReleaseWriter();
        IterateAtForkHandlerSets([] (const TAtForkHandlerSet& set) {
            if (set.Child) {
                set.Child();
            }
        });
    }

    template <class F>
    void IterateAtForkHandlerSets(F func)
    {
        for (const auto& set : AtForkHandlerSets_) {
            if (set.Initialized.load()) {
                func(set);
            }
        }
    }
};

////////////////////////////////////////////////////////////////////////////////

static void* AtForkManagerInitializer = [] { return TAtForkManager::Get(); }();

////////////////////////////////////////////////////////////////////////////////

void RegisterAtForkHandlers(
    TAtForkHandler prepare,
    TAtForkHandler parent,
    TAtForkHandler child)
{
    return TAtForkManager::Get()->RegisterAtForkHandlers(
        std::move(prepare),
        std::move(parent),
        std::move(child));
}

TReaderWriterSpinLock* GetForkLock()
{
    return TAtForkManager::Get()->GetForkLock();
}

////////////////////////////////////////////////////////////////////////////////

} // namespace NYT::NThreading