src/mcas/ptst.c

   1 /******************************************************************************
   2  * ptst.c
   3  *
   4  * Per-thread state management. Essentially the state management parts
   5  * of MB's garbage-collection code have been pulled out and placed here,
   6  * for the use of other utility routines.
   7  *
   8  * Copyright (c) 2002-2003, K A Fraser
   9
  10 Redistribution and use in source and binary forms, with or without
  11 modification, are permitted provided that the following conditions are
  12 met:
  13
  14     * Redistributions of source code must retain the above copyright
  15     * notice, this list of conditions and the following disclaimer.
  16     * Redistributions in binary form must reproduce the above
  17     * copyright notice, this list of conditions and the following
  18     * disclaimer in the documentation and/or other materials provided
  19     * with the distribution.  Neither the name of the Keir Fraser
  20     * nor the names of its contributors may be used to endorse or
  21     * promote products derived from this software without specific
  22     * prior written permission.
  23
  24 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  25 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  26 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  27 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  28 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  29 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  30 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  31 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  32 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  33 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  34 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  35  */
  36
  37 #include <stdio.h>
  38 #include <stdlib.h>
  39 #include <string.h>
  40 #include "portable_defns.h"
  41 #include "ptst.h"
  42
  43
  44 pthread_key_t ptst_key;
  45 ptst_t *ptst_list;
  46
  47 static unsigned int next_id;
  48
  49 ptst_t *critical_enter(void)
  50 {
  51     ptst_t *ptst, *next, *new_next;
  52     unsigned int id, oid;
  53
  54     ptst = (ptst_t *)pthread_getspecific(ptst_key);
  55     if ( ptst == NULL )
  56     {
  57         for ( ptst = ptst_first(); ptst != NULL; ptst = ptst_next(ptst) )
  58         {
  59             if ( (ptst->count == 0) && (CASIO(&ptst->count, 0, 1) == 0) )
  60             {
  61                 break;
  62             }
  63         }
  64
  65         if ( ptst == NULL )
  66         {
  67             ptst = ALIGNED_ALLOC(sizeof(*ptst));
  68             if ( ptst == NULL ) exit(1);
  69             memset(ptst, 0, sizeof(*ptst));
  70             ptst->gc = gc_init();
  71             rand_init(ptst);
  72             ptst->count = 1;
  73             id = next_id;
  74             while ( (oid = CASIO(&next_id, id, id+1)) != id ) id = oid;
  75             ptst->id = id;
  76             new_next = ptst_list;
  77             do {
  78                 ptst->next = next = new_next;
  79                 WMB_NEAR_CAS();
  80             }
  81             while ( (new_next = CASPO(&ptst_list, next, ptst)) != next );
  82         }
  83
  84         pthread_setspecific(ptst_key, ptst);
  85     }
  86
  87     gc_enter(ptst);
  88     return(ptst);
  89 }
  90
  91
  92 static void ptst_destructor(ptst_t *ptst)
  93 {
  94     ptst->count = 0;
  95 }
  96
  97
  98 void _init_ptst_subsystem(void)
  99 {
 100     ptst_list = NULL;
 101     next_id   = 0;
 102     WMB();
 103     if ( pthread_key_create(&ptst_key, (void (*)(void *))ptst_destructor) )
 104     {
 105         exit(1);
 106     }
 107 }