libitm/config/linux/futex.cc

   1 /* Copyright (C) 2008-2024 Free Software Foundation, Inc.
   2    Contributed by Richard Henderson <rth@redhat.com>.
   3
   4    This file is part of the GNU Transactional Memory Library (libitm).
   5
   6    Libitm is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    Libitm is distributed in the hope that it will be useful, but WITHOUT ANY
  12    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  13    FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  14    more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 /* Provide access to the futex system call.  */
  26
  27 #include "libitm_i.h"
  28 #include "futex.h"
  29 #include <futex_bits.h>
  30 #include <errno.h>
  31
  32 namespace GTM HIDDEN {
  33
  34 #define FUTEX_WAIT              0
  35 #define FUTEX_WAKE              1
  36 #define FUTEX_PRIVATE_FLAG      128
  37
  38
  39 static int gtm_futex_wait = FUTEX_WAIT | FUTEX_PRIVATE_FLAG;
  40 static int gtm_futex_wake = FUTEX_WAKE | FUTEX_PRIVATE_FLAG;
  41
  42
  43 void
  44 futex_wait (std::atomic<int> *addr, int val)
  45 {
  46   long res;
  47
  48   res = sys_futex0 (addr, gtm_futex_wait, val);
  49   if (__builtin_expect (res == -ENOSYS, 0))
  50     {
  51       gtm_futex_wait = FUTEX_WAIT;
  52       gtm_futex_wake = FUTEX_WAKE;
  53       res = sys_futex0 (addr, FUTEX_WAIT, val);
  54     }
  55   if (__builtin_expect (res < 0, 0))
  56     {
  57       if (res == -EWOULDBLOCK || res == -ETIMEDOUT)
  58         ;
  59       else if (res == -EFAULT)
  60         GTM_fatal ("futex failed (EFAULT %p)", addr);
  61       else
  62         GTM_fatal ("futex failed (%s)", strerror(-res));
  63     }
  64 }
  65
  66
  67 long
  68 futex_wake (std::atomic<int> *addr, int count)
  69 {
  70   long res = sys_futex0 (addr, gtm_futex_wake, count);
  71   if (__builtin_expect (res == -ENOSYS, 0))
  72     {
  73       gtm_futex_wait = FUTEX_WAIT;
  74       gtm_futex_wake = FUTEX_WAKE;
  75       res = sys_futex0 (addr, FUTEX_WAKE, count);
  76     }
  77   if (__builtin_expect (res < 0, 0))
  78     GTM_fatal ("futex failed (%s)", strerror(-res));
  79   else
  80     return res;
  81 }
  82
  83 } // namespace GTM