1  /* low level locking for pthread library.  Generic futex-using version.
       2     Copyright (C) 2003-2023 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     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <sysdep.h>
      20  #include <futex-internal.h>
      21  #include <atomic.h>
      22  #include <stap-probe.h>
      23  
      24  void
      25  __lll_lock_wait_private (int *futex)
      26  {
      27    if (atomic_load_relaxed (futex) == 2)
      28      goto futex;
      29  
      30    while (atomic_exchange_acquire (futex, 2) != 0)
      31      {
      32      futex:
      33        LIBC_PROBE (lll_lock_wait_private, 1, futex);
      34        futex_wait ((unsigned int *) futex, 2, LLL_PRIVATE); /* Wait if *futex == 2.  */
      35      }
      36  }
      37  libc_hidden_def (__lll_lock_wait_private)
      38  
      39  void
      40  __lll_lock_wait (int *futex, int private)
      41  {
      42    if (atomic_load_relaxed (futex) == 2)
      43      goto futex;
      44  
      45    while (atomic_exchange_acquire (futex, 2) != 0)
      46      {
      47      futex:
      48        LIBC_PROBE (lll_lock_wait, 1, futex);
      49        futex_wait ((unsigned int *) futex, 2, private); /* Wait if *futex == 2.  */
      50      }
      51  }
      52  libc_hidden_def (__lll_lock_wait)
      53  
      54  void
      55  __lll_lock_wake_private (int *futex)
      56  {
      57    lll_futex_wake (futex, 1, LLL_PRIVATE);
      58  }
      59  libc_hidden_def (__lll_lock_wake_private)
      60  
      61  void
      62  __lll_lock_wake (int *futex, int private)
      63  {
      64    lll_futex_wake (futex, 1, private);
      65  }
      66  libc_hidden_def (__lll_lock_wake)
      67  
      68  #if ENABLE_ELISION_SUPPORT
      69  int __pthread_force_elision;
      70  libc_hidden_data_def (__pthread_force_elision)
      71  #endif