nptl/pthread_mutex_init.c

   1 /* Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <assert.h>
  21 #include <errno.h>
  22 #include <string.h>
  23 #include "pthreadP.h"
  24
  25 static const struct pthread_mutexattr default_attr =
  26   {
  27     /* Default is a normal mutex, not shared between processes.  */
  28     .mutexkind = PTHREAD_MUTEX_NORMAL
  29   };
  30
  31
  32 #ifndef __ASSUME_FUTEX_LOCK_PI
  33 static int tpi_supported;
  34 #endif
  35
  36
  37 int
  38 __pthread_mutex_init (mutex, mutexattr)
  39      pthread_mutex_t *mutex;
  40      const pthread_mutexattr_t *mutexattr;
  41 {
  42   const struct pthread_mutexattr *imutexattr;
  43
  44   assert (sizeof (pthread_mutex_t) <= __SIZEOF_PTHREAD_MUTEX_T);
  45
  46   imutexattr = (const struct pthread_mutexattr *) mutexattr ?: &default_attr;
  47
  48   /* Sanity checks.  */
  49   switch (__builtin_expect (imutexattr->mutexkind
  50                             & PTHREAD_MUTEXATTR_PROTOCOL_MASK,
  51                             PTHREAD_PRIO_NONE
  52                             << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT))
  53     {
  54     case PTHREAD_PRIO_NONE << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
  55       break;
  56
  57     case PTHREAD_PRIO_INHERIT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
  58 #ifndef __ASSUME_FUTEX_LOCK_PI
  59       if (__builtin_expect (tpi_supported == 0, 0))
  60         {
  61           int lock = 0;
  62           INTERNAL_SYSCALL_DECL (err);
  63           int ret = INTERNAL_SYSCALL (futex, err, 4, &lock, FUTEX_UNLOCK_PI,
  64                                       0, 0);
  65           assert (INTERNAL_SYSCALL_ERROR_P (ret, err));
  66           tpi_supported = INTERNAL_SYSCALL_ERRNO (ret, err) == ENOSYS ? -1 : 1;
  67         }
  68       if (__builtin_expect (tpi_supported < 0, 0))
  69         return ENOTSUP;
  70 #endif
  71       break;
  72
  73     default:
  74       /* XXX: For now we don't support robust priority protected mutexes.  */
  75       if (imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_ROBUST)
  76         return ENOTSUP;
  77       break;
  78     }
  79
  80   /* Clear the whole variable.  */
  81   memset (mutex, '\0', __SIZEOF_PTHREAD_MUTEX_T);
  82
  83   /* Copy the values from the attribute.  */
  84   mutex->__data.__kind = imutexattr->mutexkind & ~PTHREAD_MUTEXATTR_FLAG_BITS;
  85
  86   if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_ROBUST) != 0)
  87     {
  88 #ifndef __ASSUME_SET_ROBUST_LIST
  89       if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_PSHARED) != 0
  90           && __set_robust_list_avail < 0)
  91         return ENOTSUP;
  92 #endif
  93
  94       mutex->__data.__kind |= PTHREAD_MUTEX_ROBUST_NORMAL_NP;
  95     }
  96
  97   switch (imutexattr->mutexkind & PTHREAD_MUTEXATTR_PROTOCOL_MASK)
  98     {
  99     case PTHREAD_PRIO_INHERIT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
 100       mutex->__data.__kind |= PTHREAD_MUTEX_PRIO_INHERIT_NP;
 101       break;
 102
 103     case PTHREAD_PRIO_PROTECT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
 104       mutex->__data.__kind |= PTHREAD_MUTEX_PRIO_PROTECT_NP;
 105
 106       int ceiling = (imutexattr->mutexkind
 107                      & PTHREAD_MUTEXATTR_PRIO_CEILING_MASK)
 108                     >> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT;
 109       if (! ceiling)
 110         {
 111           if (__sched_fifo_min_prio == -1)
 112             __init_sched_fifo_prio ();
 113           if (ceiling < __sched_fifo_min_prio)
 114             ceiling = __sched_fifo_min_prio;
 115         }
 116       mutex->__data.__lock = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 117       break;
 118
 119     default:
 120       break;
 121     }
 122
 123   /* Default values: mutex not used yet.  */
 124   // mutex->__count = 0;        already done by memset
 125   // mutex->__owner = 0;        already done by memset
 126   // mutex->__nusers = 0;       already done by memset
 127   // mutex->__spins = 0;        already done by memset
 128   // mutex->__next = NULL;      already done by memset
 129
 130   return 0;
 131 }
 132 strong_alias (__pthread_mutex_init, pthread_mutex_init)
 133 INTDEF(__pthread_mutex_init)