sysdeps/unix/sysv/linux/futex-internal.h

   1 /* futex operations for glibc-internal use.  Linux version.
   2    Copyright (C) 2014-2016 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   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 #ifndef FUTEX_INTERNAL_H
  20 #define FUTEX_INTERNAL_H
  21
  22 #include <sysdeps/nptl/futex-internal.h>
  23 #include <errno.h>
  24 #include <lowlevellock-futex.h>
  25 #include <nptl/pthreadP.h>
  26
  27 /* See sysdeps/nptl/futex-internal.h for documentation; this file only
  28    contains Linux-specific comments.
  29
  30    The Linux kernel treats provides absolute timeouts based on the
  31    CLOCK_REALTIME clock and relative timeouts measured against the
  32    CLOCK_MONOTONIC clock.
  33
  34    We expect a Linux kernel version of 2.6.22 or more recent (since this
  35    version, EINTR is not returned on spurious wake-ups anymore).  */
  36
  37 /* FUTEX_SHARED is always supported by the Linux kernel.  */
  38 static __always_inline int
  39 futex_supports_pshared (int pshared)
  40 {
  41   if (__glibc_likely (pshared == PTHREAD_PROCESS_PRIVATE))
  42     return 0;
  43   else if (pshared == PTHREAD_PROCESS_SHARED)
  44     return 0;
  45   else
  46     return EINVAL;
  47 }
  48
  49 /* The Linux kernel supports relative timeouts measured against the
  50    CLOCK_MONOTONIC clock.  */
  51 static __always_inline bool
  52 futex_supports_exact_relative_timeouts (void)
  53 {
  54   return true;
  55 }
  56
  57 /* See sysdeps/nptl/futex-internal.h for details.  */
  58 static __always_inline int
  59 futex_wait (unsigned int *futex_word, unsigned int expected, int private)
  60 {
  61   int err = lll_futex_timed_wait (futex_word, expected, NULL, private);
  62   switch (err)
  63     {
  64     case 0:
  65     case -EAGAIN:
  66     case -EINTR:
  67       return -err;
  68
  69     case -ETIMEDOUT: /* Cannot have happened as we provided no timeout.  */
  70     case -EFAULT: /* Must have been caused by a glibc or application bug.  */
  71     case -EINVAL: /* Either due to wrong alignment or due to the timeout not
  72                      being normalized.  Must have been caused by a glibc or
  73                      application bug.  */
  74     case -ENOSYS: /* Must have been caused by a glibc bug.  */
  75     /* No other errors are documented at this time.  */
  76     default:
  77       futex_fatal_error ();
  78     }
  79 }
  80
  81 /* See sysdeps/nptl/futex-internal.h for details.  */
  82 static __always_inline int
  83 futex_wait_cancelable (unsigned int *futex_word, unsigned int expected,
  84                        int private)
  85 {
  86   int oldtype;
  87   oldtype = __pthread_enable_asynccancel ();
  88   int err = lll_futex_timed_wait (futex_word, expected, NULL, private);
  89   __pthread_disable_asynccancel (oldtype);
  90   switch (err)
  91     {
  92     case 0:
  93     case -EAGAIN:
  94     case -EINTR:
  95       return -err;
  96
  97     case -ETIMEDOUT: /* Cannot have happened as we provided no timeout.  */
  98     case -EFAULT: /* Must have been caused by a glibc or application bug.  */
  99     case -EINVAL: /* Either due to wrong alignment or due to the timeout not
 100                      being normalized.  Must have been caused by a glibc or
 101                      application bug.  */
 102     case -ENOSYS: /* Must have been caused by a glibc bug.  */
 103     /* No other errors are documented at this time.  */
 104     default:
 105       futex_fatal_error ();
 106     }
 107 }
 108
 109 /* See sysdeps/nptl/futex-internal.h for details.  */
 110 static __always_inline int
 111 futex_reltimed_wait (unsigned int *futex_word, unsigned int expected,
 112                      const struct timespec *reltime, int private)
 113 {
 114   int err = lll_futex_timed_wait (futex_word, expected, reltime, private);
 115   switch (err)
 116     {
 117     case 0:
 118     case -EAGAIN:
 119     case -EINTR:
 120     case -ETIMEDOUT:
 121       return -err;
 122
 123     case -EFAULT: /* Must have been caused by a glibc or application bug.  */
 124     case -EINVAL: /* Either due to wrong alignment or due to the timeout not
 125                      being normalized.  Must have been caused by a glibc or
 126                      application bug.  */
 127     case -ENOSYS: /* Must have been caused by a glibc bug.  */
 128     /* No other errors are documented at this time.  */
 129     default:
 130       futex_fatal_error ();
 131     }
 132 }
 133
 134 /* See sysdeps/nptl/futex-internal.h for details.  */
 135 static __always_inline int
 136 futex_reltimed_wait_cancelable (unsigned int *futex_word,
 137                                 unsigned int expected,
 138                                 const struct timespec *reltime, int private)
 139 {
 140   int oldtype;
 141   oldtype = __pthread_enable_asynccancel ();
 142   int err = lll_futex_timed_wait (futex_word, expected, reltime, private);
 143   __pthread_disable_asynccancel (oldtype);
 144   switch (err)
 145     {
 146     case 0:
 147     case -EAGAIN:
 148     case -EINTR:
 149     case -ETIMEDOUT:
 150       return -err;
 151
 152     case -EFAULT: /* Must have been caused by a glibc or application bug.  */
 153     case -EINVAL: /* Either due to wrong alignment or due to the timeout not
 154                      being normalized.  Must have been caused by a glibc or
 155                      application bug.  */
 156     case -ENOSYS: /* Must have been caused by a glibc bug.  */
 157     /* No other errors are documented at this time.  */
 158     default:
 159       futex_fatal_error ();
 160     }
 161 }
 162
 163 /* See sysdeps/nptl/futex-internal.h for details.  */
 164 static __always_inline int
 165 futex_abstimed_wait (unsigned int *futex_word, unsigned int expected,
 166                      const struct timespec *abstime, int private)
 167 {
 168   /* Work around the fact that the kernel rejects negative timeout values
 169      despite them being valid.  */
 170   if (__glibc_unlikely ((abstime != NULL) && (abstime->tv_sec < 0)))
 171     return ETIMEDOUT;
 172   int err = lll_futex_timed_wait_bitset (futex_word, expected, abstime,
 173                                          FUTEX_CLOCK_REALTIME, private);
 174   switch (err)
 175     {
 176     case 0:
 177     case -EAGAIN:
 178     case -EINTR:
 179     case -ETIMEDOUT:
 180       return -err;
 181
 182     case -EFAULT: /* Must have been caused by a glibc or application bug.  */
 183     case -EINVAL: /* Either due to wrong alignment or due to the timeout not
 184                      being normalized.  Must have been caused by a glibc or
 185                      application bug.  */
 186     case -ENOSYS: /* Must have been caused by a glibc bug.  */
 187     /* No other errors are documented at this time.  */
 188     default:
 189       futex_fatal_error ();
 190     }
 191 }
 192
 193 /* See sysdeps/nptl/futex-internal.h for details.  */
 194 static __always_inline int
 195 futex_abstimed_wait_cancelable (unsigned int *futex_word,
 196                                 unsigned int expected,
 197                                 const struct timespec *abstime, int private)
 198 {
 199   /* Work around the fact that the kernel rejects negative timeout values
 200      despite them being valid.  */
 201   if (__glibc_unlikely ((abstime != NULL) && (abstime->tv_sec < 0)))
 202     return ETIMEDOUT;
 203   int oldtype;
 204   oldtype = __pthread_enable_asynccancel ();
 205   int err = lll_futex_timed_wait_bitset (futex_word, expected, abstime,
 206                                          FUTEX_CLOCK_REALTIME, private);
 207   __pthread_disable_asynccancel (oldtype);
 208   switch (err)
 209     {
 210     case 0:
 211     case -EAGAIN:
 212     case -EINTR:
 213     case -ETIMEDOUT:
 214       return -err;
 215
 216     case -EFAULT: /* Must have been caused by a glibc or application bug.  */
 217     case -EINVAL: /* Either due to wrong alignment or due to the timeout not
 218                      being normalized.  Must have been caused by a glibc or
 219                      application bug.  */
 220     case -ENOSYS: /* Must have been caused by a glibc bug.  */
 221     /* No other errors are documented at this time.  */
 222     default:
 223       futex_fatal_error ();
 224     }
 225 }
 226
 227 /* See sysdeps/nptl/futex-internal.h for details.  */
 228 static __always_inline void
 229 futex_wake (unsigned int *futex_word, int processes_to_wake, int private)
 230 {
 231   int res = lll_futex_wake (futex_word, processes_to_wake, private);
 232   /* No error.  Ignore the number of woken processes.  */
 233   if (res >= 0)
 234     return;
 235   switch (res)
 236     {
 237     case -EFAULT: /* Could have happened due to memory reuse.  */
 238     case -EINVAL: /* Could be either due to incorrect alignment (a bug in
 239                      glibc or in the application) or due to memory being
 240                      reused for a PI futex.  We cannot distinguish between the
 241                      two causes, and one of them is correct use, so we do not
 242                      act in this case.  */
 243       return;
 244     case -ENOSYS: /* Must have been caused by a glibc bug.  */
 245     /* No other errors are documented at this time.  */
 246     default:
 247       futex_fatal_error ();
 248     }
 249 }
 250
 251 #endif  /* futex-internal.h */