text: /* Low level locking macros used in NPTL implementation.  Stub version.
     Copyright (C) 2002, 2007 Free Software Foundation, Inc.
     This file is part of the GNU C Library.
     Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
  
     The GNU C Library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Lesser General Public
     License as published by the Free Software Foundation; either
     version 2.1 of the License, or (at your option) any later version.
  
     The GNU C Library is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Lesser General Public License for more details.
  
     You should have received a copy of the GNU Lesser General Public
     License along with the GNU C Library; if not, write to the Free
     Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
     02111-1307 USA.  */
  
  #include <atomic.h>
  
  
  /* Mutex lock counter:
     bit 31 clear means unlocked;
     bit 31 set means locked.
  
     All code that looks at bit 31 first increases the 'number of
     interested threads' usage counter, which is in bits 0-30.
  
     All negative mutex values indicate that the mutex is still locked.  */
  
  
  static inline void
  __generic_mutex_lock (int *mutex)
  {
    unsigned int v;
  
    /* Bit 31 was clear, we got the mutex.  (this is the fastpath).  */
    if (atomic_bit_test_set (mutex, 31) == 0)
      return;
  
    atomic_increment (mutex);
  
    while (1)
      {
        if (atomic_bit_test_set (mutex, 31) == 0)
  	{
  	  atomic_decrement (mutex);
  	  return;
  	}
  
        /* We have to wait now. First make sure the futex value we are
  	 monitoring is truly negative (i.e. locked). */
        v = *mutex;
        if (v >= 0)
  	continue;
  
        lll_futex_wait (mutex, v,
  		      // XYZ check mutex flag
  		      LLL_SHARED);
      }
  }
  
  
  static inline void
  __generic_mutex_unlock (int *mutex)
  {
    /* Adding 0x80000000 to the counter results in 0 if and only if
       there are not other interested threads - we can return (this is
       the fastpath).  */
    if (atomic_add_zero (mutex, 0x80000000))
      return;
  
    /* There are other threads waiting for this mutex, wake one of them
       up.  */
    lll_futex_wake (mutex, 1,
  		  // XYZ check mutex flag
  		  LLL_SHARED);
  }
  
  
  #define lll_mutex_lock(futex) __generic_mutex_lock (&(futex))
  #define lll_mutex_unlock(futex) __generic_mutex_unlock (&(futex))
  