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       1                 :            : /***
       2                 :            :   This file is part of PulseAudio.
       3                 :            : 
       4                 :            :   Copyright 2006 Lennart Poettering
       5                 :            : 
       6                 :            :   PulseAudio is free software; you can redistribute it and/or modify
       7                 :            :   it under the terms of the GNU Lesser General Public License as published
       8                 :            :   by the Free Software Foundation; either version 2.1 of the License,
       9                 :            :   or (at your option) any later version.
      10                 :            : 
      11                 :            :   PulseAudio is distributed in the hope that it will be useful, but
      12                 :            :   WITHOUT ANY WARRANTY; without even the implied warranty of
      13                 :            :   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
      14                 :            :   General Public License for more details.
      15                 :            : 
      16                 :            :   You should have received a copy of the GNU Lesser General Public License
      17                 :            :   along with PulseAudio; if not, write to the Free Software
      18                 :            :   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
      19                 :            :   USA.
      20                 :            : ***/
      21                 :            : 
      22                 :            : #ifdef HAVE_CONFIG_H
      23                 :            : #include <config.h>
      24                 :            : #endif
      25                 :            : 
      26                 :            : #include <pulsecore/macro.h>
      27                 :            : 
      28                 :            : #include "once.h"
      29                 :            : 
      30                 :            : /* See http://www.hpl.hp.com/research/linux/atomic_ops/example.php4 for the
      31                 :            :  * reference algorithm used here. */
      32                 :            : 
      33                 :     214305 : pa_bool_t pa_once_begin(pa_once *control) {
      34                 :            :     pa_mutex *m;
      35                 :            : 
      36         [ -  + ]:     214305 :     pa_assert(control);
      37                 :            : 
      38         [ +  + ]:     214305 :     if (pa_atomic_load(&control->done))
      39                 :            :         return FALSE;
      40                 :            : 
      41                 :            :     /* Caveat: We have to make sure that the once func has completed
      42                 :            :      * before returning, even if the once func is not actually
      43                 :            :      * executed by us. Hence the awkward locking. */
      44                 :            : 
      45                 :       1467 :     m = pa_static_mutex_get(&control->mutex, FALSE, FALSE);
      46                 :       1451 :     pa_mutex_lock(m);
      47                 :            : 
      48         [ +  + ]:       1483 :     if (pa_atomic_load(&control->done)) {
      49                 :        937 :         pa_mutex_unlock(m);
      50                 :     214314 :         return FALSE;
      51                 :            :     }
      52                 :            : 
      53                 :            :     return TRUE;
      54                 :            : }
      55                 :            : 
      56                 :        546 : void pa_once_end(pa_once *control) {
      57                 :            :     pa_mutex *m;
      58                 :            : 
      59         [ -  + ]:        546 :     pa_assert(control);
      60                 :            : 
      61         [ -  + ]:        546 :     pa_assert(!pa_atomic_load(&control->done));
      62                 :        546 :     pa_atomic_store(&control->done, 1);
      63                 :            : 
      64                 :        546 :     m = pa_static_mutex_get(&control->mutex, FALSE, FALSE);
      65                 :        546 :     pa_mutex_unlock(m);
      66                 :        546 : }
      67                 :            : 
      68                 :            : /* Not reentrant -- how could it be? */
      69                 :      99434 : void pa_run_once(pa_once *control, pa_once_func_t func) {
      70         [ -  + ]:      99434 :     pa_assert(control);
      71         [ -  + ]:      99434 :     pa_assert(func);
      72                 :            : 
      73         [ +  + ]:      99434 :     if (pa_once_begin(control)) {
      74                 :        517 :         func();
      75                 :        517 :         pa_once_end(control);
      76                 :            :     }
      77                 :     100167 : }