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