simple_semaphore.hpp 6.17 KB
Newer Older
Martin Sustrik's avatar
Martin Sustrik committed
1
/*
2
    Copyright (c) 2007-2010 iMatix Corporation
Martin Sustrik's avatar
Martin Sustrik committed
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

    This file is part of 0MQ.

    0MQ is free software; you can redistribute it and/or modify it under
    the terms of the Lesser GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    0MQ 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
    Lesser GNU General Public License for more details.

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

Martin Sustrik's avatar
Martin Sustrik committed
20 21
#ifndef __ZMQ_SIMPLE_SEMAPHORE_HPP_INCLUDED__
#define __ZMQ_SIMPLE_SEMAPHORE_HPP_INCLUDED__
Martin Sustrik's avatar
Martin Sustrik committed
22 23 24 25

#include "platform.hpp"
#include "err.hpp"

26 27 28 29 30
#if 0 //defined ZMQ_HAVE_LINUX
#include <sys/syscall.h>
#include <unistd.h>
#include <linux/futex.h>
#elif defined ZMQ_HAVE_LINUX ||defined ZMQ_HAVE_OSX || defined ZMQ_HAVE_OPENVMS
Martin Sustrik's avatar
Martin Sustrik committed
31
#include <pthread.h>
Martin Sustrik's avatar
Martin Sustrik committed
32
#elif defined ZMQ_HAVE_WINDOWS
Martin Sustrik's avatar
Martin Sustrik committed
33 34 35 36 37
#include "windows.hpp"
#else
#include <semaphore.h>
#endif

Martin Sustrik's avatar
Martin Sustrik committed
38
namespace zmq
Martin Sustrik's avatar
Martin Sustrik committed
39 40 41 42 43 44
{
    //  Simple semaphore. Only single thread may be waiting at any given time.
    //  Also, the semaphore may not be posted before the previous post
    //  was matched by corresponding wait and the waiting thread was
    //  released.

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
#if 0 //defined ZMQ_HAVE_LINUX

    //  In theory, using private futexes should be more efficient on Linux
    //  platform than using mutexes. However, in uncontended cases of TCP
    //  transport on loopback interface we haven't seen any latency improvement.
    //  The code is commented out waiting for more thorough testing.

    class simple_semaphore_t
    { 
    public:

        //  Initialise the semaphore.
        inline simple_semaphore_t () :
            dummy (0)
        {
        }

        //  Destroy the semaphore.
        inline ~simple_semaphore_t ()
        {
        }

        //  Wait for the semaphore.
        inline void wait ()
        {
            int rc = syscall (SYS_futex, &dummy, (int) FUTEX_WAIT_PRIVATE,
                (int) 0, NULL, NULL, (int) 0);
            zmq_assert (rc == 0);
        }

        //  Post the semaphore.
        inline void post ()
        {
            while (true) {
                int rc = syscall (SYS_futex, &dummy, (int) FUTEX_WAKE_PRIVATE,
                    (int) 1, NULL, NULL, (int) 0);
                zmq_assert (rc != -1 && rc <= 1);
                if (rc == 1)
                    break;
            }
        }

    private:

        int dummy;

        //  Disable copying of the object.
        simple_semaphore_t (const simple_semaphore_t&);
        void operator = (const simple_semaphore_t&);
    };

#elif defined ZMQ_HAVE_LINUX || defined ZMQ_HAVE_OSX || defined ZMQ_HAVE_OPENVMS
Martin Sustrik's avatar
Martin Sustrik committed
97 98 99 100 101 102 103 104 105 106 107 108 109

    //  On platforms that allow for double locking of a mutex from the same
    //  thread, simple semaphore is implemented using mutex, as it is more
    //  efficient than full-blown semaphore.

    class simple_semaphore_t
    { 
    public:

        //  Initialise the semaphore.
        inline simple_semaphore_t ()
        {
            int rc = pthread_mutex_init (&mutex, NULL);
110
            posix_assert (rc);
Martin Sustrik's avatar
Martin Sustrik committed
111
            rc = pthread_mutex_lock (&mutex);
112
            posix_assert (rc);
Martin Sustrik's avatar
Martin Sustrik committed
113 114 115 116 117 118
        }

        //  Destroy the semaphore.
        inline ~simple_semaphore_t ()
        {
            int rc = pthread_mutex_unlock (&mutex);
119
            posix_assert (rc);
Martin Sustrik's avatar
Martin Sustrik committed
120
            rc = pthread_mutex_destroy (&mutex);
121
            posix_assert (rc);
Martin Sustrik's avatar
Martin Sustrik committed
122 123 124 125 126 127
        }

        //  Wait for the semaphore.
        inline void wait ()
        {
             int rc = pthread_mutex_lock (&mutex);
128
             posix_assert (rc);
Martin Sustrik's avatar
Martin Sustrik committed
129 130 131 132 133 134
        }

        //  Post the semaphore.
        inline void post ()
        {
            int rc = pthread_mutex_unlock (&mutex);
135
            posix_assert (rc);
Martin Sustrik's avatar
Martin Sustrik committed
136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242
        }

    private:

        pthread_mutex_t mutex;

        //  Disable copying of the object.
        simple_semaphore_t (const simple_semaphore_t&);
        void operator = (const simple_semaphore_t&);
    };

#elif defined ZMQ_HAVE_WINDOWS

    //  On Windows platform simple semaphore is implemeted using event object.

    class simple_semaphore_t
    { 
    public:

        //  Initialise the semaphore.
        inline simple_semaphore_t ()
        {
            ev = CreateEvent (NULL, FALSE, FALSE, NULL);
            win_assert (ev != NULL);
        }

        //  Destroy the semaphore.
        inline ~simple_semaphore_t ()
        {
            int rc = CloseHandle (ev);
            win_assert (rc != 0);    
        }

        //  Wait for the semaphore.
        inline void wait ()
        {
            DWORD rc = WaitForSingleObject (ev, INFINITE);
            win_assert (rc != WAIT_FAILED);
        }

        //  Post the semaphore.
        inline void post ()
        {
            int rc = SetEvent (ev);
            win_assert (rc != 0);
        }

    private:

        HANDLE ev;

        //  Disable copying of the object.
        simple_semaphore_t (const simple_semaphore_t&);
        void operator = (const simple_semaphore_t&);
    };

#else

    //  Default implementation maps simple semaphore to standard semaphore.

    class simple_semaphore_t
    { 
    public:

        //  Initialise the semaphore.
        inline simple_semaphore_t ()
        {
             int rc = sem_init (&sem, 0, 0);
             errno_assert (rc != -1);
        }

        //  Destroy the semaphore.
        inline ~simple_semaphore_t ()
        {
             int rc = sem_destroy (&sem);
             errno_assert (rc != -1);
        }

        //  Wait for the semaphore.
        inline void wait ()
        {
             int rc = sem_wait (&sem);
             errno_assert (rc != -1);
        }

        //  Post the semaphore.
        inline void post ()
        {
            int rc = sem_post (&sem);
            errno_assert (rc != -1);
        }

    private:

        //  Underlying system semaphore object.
        sem_t sem;

        //  Disable copying of the object.
        simple_semaphore_t (const simple_semaphore_t&);
        void operator = (const simple_semaphore_t&);
    };

#endif

}

#endif