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

   1 /* futex operations for glibc-internal use.  Linux version.
   2    Copyright (C) 2014-2019 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 <sysdep-cancel.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 = LIBC_CANCEL_ASYNC ();
 142   int err = lll_futex_timed_wait (futex_word, expected, reltime, private);
 143   LIBC_CANCEL_RESET (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_supported_clockid (clockid_t clockid)
 166 {
 167   return lll_futex_supported_clockid (clockid);
 168 }
 169
 170 /* See sysdeps/nptl/futex-internal.h for details.  */
 171 static __always_inline int
 172 futex_abstimed_wait (unsigned int *futex_word, unsigned int expected,
 173                      clockid_t clockid,
 174                      const struct timespec *abstime, int private)
 175 {
 176   /* Work around the fact that the kernel rejects negative timeout values
 177      despite them being valid.  */
 178   if (__glibc_unlikely ((abstime != NULL) && (abstime->tv_sec < 0)))
 179     return ETIMEDOUT;
 180   int err = lll_futex_clock_wait_bitset (futex_word, expected,
 181                                          clockid, abstime,
 182                                          private);
 183   switch (err)
 184     {
 185     case 0:
 186     case -EAGAIN:
 187     case -EINTR:
 188     case -ETIMEDOUT:
 189       return -err;
 190
 191     case -EFAULT: /* Must have been caused by a glibc or application bug.  */
 192     case -EINVAL: /* Either due to wrong alignment, unsupported
 193                      clockid or due to the timeout not being
 194                      normalized. Must have been caused by a glibc or
 195                      application bug.  */
 196     case -ENOSYS: /* Must have been caused by a glibc bug.  */
 197     /* No other errors are documented at this time.  */
 198     default:
 199       futex_fatal_error ();
 200     }
 201 }
 202
 203 /* See sysdeps/nptl/futex-internal.h for details.  */
 204 static __always_inline int
 205 futex_abstimed_wait_cancelable (unsigned int *futex_word,
 206                                 unsigned int expected,
 207                                 clockid_t clockid,
 208                                 const struct timespec *abstime, int private)
 209 {
 210   /* Work around the fact that the kernel rejects negative timeout values
 211      despite them being valid.  */
 212   if (__glibc_unlikely ((abstime != NULL) && (abstime->tv_sec < 0)))
 213     return ETIMEDOUT;
 214   int oldtype;
 215   oldtype = __pthread_enable_asynccancel ();
 216   int err = lll_futex_clock_wait_bitset (futex_word, expected,
 217                                         clockid, abstime,
 218                                         private);
 219   __pthread_disable_asynccancel (oldtype);
 220   switch (err)
 221     {
 222     case 0:
 223     case -EAGAIN:
 224     case -EINTR:
 225     case -ETIMEDOUT:
 226       return -err;
 227
 228     case -EFAULT: /* Must have been caused by a glibc or application bug.  */
 229     case -EINVAL: /* Either due to wrong alignment or due to the timeout not
 230                      being normalized.  Must have been caused by a glibc or
 231                      application bug.  */
 232     case -ENOSYS: /* Must have been caused by a glibc bug.  */
 233     /* No other errors are documented at this time.  */
 234     default:
 235       futex_fatal_error ();
 236     }
 237 }
 238
 239 /* See sysdeps/nptl/futex-internal.h for details.  */
 240 static __always_inline void
 241 futex_wake (unsigned int *futex_word, int processes_to_wake, int private)
 242 {
 243   int res = lll_futex_wake (futex_word, processes_to_wake, private);
 244   /* No error.  Ignore the number of woken processes.  */
 245   if (res >= 0)
 246     return;
 247   switch (res)
 248     {
 249     case -EFAULT: /* Could have happened due to memory reuse.  */
 250     case -EINVAL: /* Could be either due to incorrect alignment (a bug in
 251                      glibc or in the application) or due to memory being
 252                      reused for a PI futex.  We cannot distinguish between the
 253                      two causes, and one of them is correct use, so we do not
 254                      act in this case.  */
 255       return;
 256     case -ENOSYS: /* Must have been caused by a glibc bug.  */
 257     /* No other errors are documented at this time.  */
 258     default:
 259       futex_fatal_error ();
 260     }
 261 }
 262
 263 #endif  /* futex-internal.h */