nptl/pthread_mutex_init.c

   1 /* Copyright (C) 2002-2017 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <errno.h>
  21 #include <stdbool.h>
  22 #include <string.h>
  23 #include <kernel-features.h>
  24 #include "pthreadP.h"
  25 #include <atomic.h>
  26 #include <pthread-offsets.h>
  27
  28 #include <stap-probe.h>
  29
  30 static const struct pthread_mutexattr default_mutexattr =
  31   {
  32     /* Default is a normal mutex, not shared between processes.  */
  33     .mutexkind = PTHREAD_MUTEX_NORMAL
  34   };
  35
  36
  37 static bool
  38 prio_inherit_missing (void)
  39 {
  40 #ifdef __NR_futex
  41   static int tpi_supported;
  42   if (__glibc_unlikely (tpi_supported == 0))
  43     {
  44       int lock = 0;
  45       INTERNAL_SYSCALL_DECL (err);
  46       int ret = INTERNAL_SYSCALL (futex, err, 4, &lock, FUTEX_UNLOCK_PI, 0, 0);
  47       assert (INTERNAL_SYSCALL_ERROR_P (ret, err));
  48       tpi_supported = INTERNAL_SYSCALL_ERRNO (ret, err) == ENOSYS ? -1 : 1;
  49     }
  50   return __glibc_unlikely (tpi_supported < 0);
  51 #endif
  52   return true;
  53 }
  54
  55 int
  56 __pthread_mutex_init (pthread_mutex_t *mutex,
  57                       const pthread_mutexattr_t *mutexattr)
  58 {
  59   const struct pthread_mutexattr *imutexattr;
  60
  61   ASSERT_TYPE_SIZE (pthread_mutex_t, __SIZEOF_PTHREAD_MUTEX_T);
  62
  63   ASSERT_PTHREAD_INTERNAL_OFFSET (pthread_mutex_t, __data.__nusers,
  64                                   __PTHREAD_MUTEX_NUSERS_OFFSET);
  65   ASSERT_PTHREAD_INTERNAL_OFFSET (pthread_mutex_t, __data.__kind,
  66                                   __PTHREAD_MUTEX_KIND_OFFSET);
  67   ASSERT_PTHREAD_INTERNAL_OFFSET (pthread_mutex_t, __data.__spins,
  68                                   __PTHREAD_MUTEX_SPINS_OFFSET);
  69 #if __PTHREAD_MUTEX_LOCK_ELISION
  70   ASSERT_PTHREAD_INTERNAL_OFFSET (pthread_mutex_t, __data.__elision,
  71                                   __PTHREAD_MUTEX_ELISION_OFFSET);
  72 #endif
  73   ASSERT_PTHREAD_INTERNAL_OFFSET (pthread_mutex_t, __data.__list,
  74                                   __PTHREAD_MUTEX_LIST_OFFSET);
  75
  76   imutexattr = ((const struct pthread_mutexattr *) mutexattr
  77                 ?: &default_mutexattr);
  78
  79   /* Sanity checks.  */
  80   switch (__builtin_expect (imutexattr->mutexkind
  81                             & PTHREAD_MUTEXATTR_PROTOCOL_MASK,
  82                             PTHREAD_PRIO_NONE
  83                             << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT))
  84     {
  85     case PTHREAD_PRIO_NONE << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
  86       break;
  87
  88     case PTHREAD_PRIO_INHERIT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
  89       if (__glibc_unlikely (prio_inherit_missing ()))
  90         return ENOTSUP;
  91       break;
  92
  93     default:
  94       /* XXX: For now we don't support robust priority protected mutexes.  */
  95       if (imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_ROBUST)
  96         return ENOTSUP;
  97       break;
  98     }
  99
 100   /* Clear the whole variable.  */
 101   memset (mutex, '\0', __SIZEOF_PTHREAD_MUTEX_T);
 102
 103   /* Copy the values from the attribute.  */
 104   mutex->__data.__kind = imutexattr->mutexkind & ~PTHREAD_MUTEXATTR_FLAG_BITS;
 105
 106   if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_ROBUST) != 0)
 107     {
 108 #ifndef __ASSUME_SET_ROBUST_LIST
 109       if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_PSHARED) != 0
 110           && __set_robust_list_avail < 0)
 111         return ENOTSUP;
 112 #endif
 113
 114       mutex->__data.__kind |= PTHREAD_MUTEX_ROBUST_NORMAL_NP;
 115     }
 116
 117   switch (imutexattr->mutexkind & PTHREAD_MUTEXATTR_PROTOCOL_MASK)
 118     {
 119     case PTHREAD_PRIO_INHERIT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
 120       mutex->__data.__kind |= PTHREAD_MUTEX_PRIO_INHERIT_NP;
 121       break;
 122
 123     case PTHREAD_PRIO_PROTECT << PTHREAD_MUTEXATTR_PROTOCOL_SHIFT:
 124       mutex->__data.__kind |= PTHREAD_MUTEX_PRIO_PROTECT_NP;
 125
 126       int ceiling = (imutexattr->mutexkind
 127                      & PTHREAD_MUTEXATTR_PRIO_CEILING_MASK)
 128                     >> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT;
 129       if (! ceiling)
 130         {
 131           /* See __init_sched_fifo_prio.  */
 132           if (atomic_load_relaxed (&__sched_fifo_min_prio) == -1)
 133             __init_sched_fifo_prio ();
 134           if (ceiling < atomic_load_relaxed (&__sched_fifo_min_prio))
 135             ceiling = atomic_load_relaxed (&__sched_fifo_min_prio);
 136         }
 137       mutex->__data.__lock = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 138       break;
 139
 140     default:
 141       break;
 142     }
 143
 144   /* The kernel when waking robust mutexes on exit never uses
 145      FUTEX_PRIVATE_FLAG FUTEX_WAKE.  */
 146   if ((imutexattr->mutexkind & (PTHREAD_MUTEXATTR_FLAG_PSHARED
 147                                 | PTHREAD_MUTEXATTR_FLAG_ROBUST)) != 0)
 148     mutex->__data.__kind |= PTHREAD_MUTEX_PSHARED_BIT;
 149
 150   /* Default values: mutex not used yet.  */
 151   // mutex->__count = 0;        already done by memset
 152   // mutex->__owner = 0;        already done by memset
 153   // mutex->__nusers = 0;       already done by memset
 154   // mutex->__spins = 0;        already done by memset
 155   // mutex->__next = NULL;      already done by memset
 156
 157   LIBC_PROBE (mutex_init, 1, mutex);
 158
 159   return 0;
 160 }
 161 weak_alias (__pthread_mutex_init, pthread_mutex_init)
 162 hidden_def (__pthread_mutex_init)