summaryrefslogtreecommitdiff
path: root/src/atomic_ptr.hpp
blob: adf1c8785f92f71457b3b938c6708dd40104b4ea (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
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
/*
    Copyright (c) 2009-2012 250bpm s.r.o.
    Copyright (c) 2007-2009 iMatix Corporation
    Copyright (c) 2007-2012 Other contributors as noted in the AUTHORS file

    This file is part of Crossroads I/O project.

    Crossroads I/O is free software; you can redistribute it and/or modify it
    under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    Crossroads 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 Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef __XS_ATOMIC_PTR_HPP_INCLUDED__
#define __XS_ATOMIC_PTR_HPP_INCLUDED__

#include <stddef.h>

#include "platform.hpp"

#if defined(XS_ATOMIC_GCC_SYNC)
#elif (defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__)))
#elif (defined(__GNUC__) && defined(__ARM_ARCH_7A__))
#elif defined(XS_ATOMIC_SOLARIS)
#   include <atomic.h>
#elif defined(XS_HAVE_WINDOWS)
#   include "windows.hpp"
#else
#   define XS_ATOMIC_OVER_MUTEX 1
#   include "mutex.hpp"
#endif

namespace xs
{

    //  This class encapsulates several atomic operations on pointers.

    template <typename T> class atomic_ptr_t
    {
    public:

        //  Initialise atomic pointer
        inline atomic_ptr_t ()
        {
            ptr = NULL;
        }

        //  Destroy atomic pointer
        inline ~atomic_ptr_t ()
        {
        }

        //  Set value of atomic pointer in a non-threadsafe way
        //  Use this function only when you are sure that at most one
        //  thread is accessing the pointer at the moment.
        inline void set (T *ptr_)
        {
            this->ptr = ptr_;
        }

        //  Perform atomic 'exchange pointers' operation. Pointer is set
        //  to the 'val' value. Old value is returned.
        inline T *xchg (T *val_)
        {
#if (defined(__GNUC__) && defined(__ARM_ARCH_7A__))
            T* old;
            unsigned int flag;
            __asm__ volatile (
                "       dmb     sy\n\t"
                "1:     ldrex   %1, [%3]\n\t"
                "       strex   %0, %4, [%3]\n\t"
                "       teq     %0, #0\n\t"
                "       bne     1b\n\t"
                "       dmb     sy\n\t"
                : "=&r"(flag), "=&r"(old), "+Qo"(ptr)
                : "r"(&ptr), "r"(val_)
                : "cc");
            return old;

#elif defined(XS_ATOMIC_GCC_SYNC)
            {
                T* ov;
                do
                {
                    ov = const_cast<T*>(ptr);
                } while (!__sync_bool_compare_and_swap (&ptr, ov, val_));
                return ov;
            }

#elif (defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__)))
            T *old;
            __asm__ volatile (
                "lock; xchg %0, %2"
                : "=r" (old), "=m" (ptr)
                : "m" (ptr), "0" (val_));
            return old;

#elif defined(XS_ATOMIC_SOLARIS)
            return (T*) atomic_swap_ptr (&ptr, val_);

#elif defined(XS_HAVE_WINDOWS)
            return (T*) InterlockedExchangePointer ((PVOID*) &ptr, val_);

#else
            sync.lock ();
            T *old = (T*) ptr;
            ptr = val_;
            sync.unlock ();
            return old;
#endif
        }

        //  Perform atomic 'compare and swap' operation on the pointer.
        //  The pointer is compared to 'cmp' argument and if they are
        //  equal, its value is set to 'val'. Old value of the pointer
        //  is returned.
        inline T *cas (T *cmp_, T *val_)
        {
#if (defined(__GNUC__) && defined(__ARM_ARCH_7A__))
            T *old;
            unsigned int flag;
            __asm__ volatile (
                "       dmb     sy\n\t"
                "1:     ldrex   %1, [%3]\n\t"
                "       mov     %0, #0\n\t"
                "       teq     %1, %4\n\t"
                "       strexeq %0, %5, [%3]\n\t"
                "       teq     %0, #0\n\t"
                "       bne     1b\n\t"
                "       dmb     sy\n\t"
                : "=&r"(flag), "=&r"(old), "+Qo"(ptr)
                : "r"(&ptr), "r"(cmp_), "r"(val_)
                : "cc");
            return old;

#elif defined(XS_ATOMIC_GCC_SYNC)
            return (T*) __sync_val_compare_and_swap (&ptr, cmp_, val_);

#elif (defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__)))
            T *old;
            __asm__ volatile (
                "lock; cmpxchg %2, %3"
                : "=a" (old), "=m" (ptr)
                : "r" (val_), "m" (ptr), "0" (cmp_)
                : "cc");
            return old;

#elif defined(XS_ATOMIC_SOLARIS)
            return (T*) atomic_cas_ptr (&ptr, cmp_, val_);

#elif defined(XS_HAVE_WINDOWS)
            return (T*) InterlockedCompareExchangePointer (
                (volatile PVOID*) &ptr, val_, cmp_);

#else
            sync.lock ();
            T *old = (T*) ptr;
            if (ptr == cmp_)
                ptr = val_;
            sync.unlock ();
            return old;
#endif
        }

    private:

        volatile T *ptr;
#if defined XS_ATOMIC_OVER_MUTEX
        mutex_t sync;
#endif

        atomic_ptr_t (const atomic_ptr_t&);
        const atomic_ptr_t &operator = (const atomic_ptr_t&);
    };

}

//  Remove macros local to this file.
#if defined(XS_ATOMIC_OVER_MUTEX)
#   undef XS_ATOMIC_OVER_MUTEX
#endif

#endif