/* elision-lock.c: Elided pthread mutex lock.

   Copyright (C) 2015-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   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, see

   <http://www.gnu.org/licenses/>.  */

#include <stdio.h>

#include <pthread.h>

#include <pthreadP.h>

#include <lowlevellock.h>

#include <elision-conf.h>

#include "htm.h"

#if !defined(LLL_LOCK) && !defined(EXTRAARG)

/* Make sure the configuration code is always linked in for static

   libraries.  */

#include "elision-conf.c"

#endif

#ifndef EXTRAARG

# define EXTRAARG

#endif

#ifndef LLL_LOCK

# define LLL_LOCK(a,b) lll_lock(a,b), 0

#endif

#define aconf __elision_aconf

/* Adaptive lock using transactions.

   By default the lock region is run as a transaction, and when it

   aborts or the lock is busy the lock adapts itself.  */

int

__lll_lock_elision (int *lock, short *adapt_count, EXTRAARG int pshared)

{

#ifndef __SPE__

  /* adapt_count is accessed concurrently but is just a hint.  Thus,

     use atomic accesses but relaxed MO is sufficient.  */

  if (atomic_load_relaxed (adapt_count) > 0)

    {

      goto use_lock;

    }

  for (int i = aconf.try_tbegin; i > 0; i--)

    {

      if (__libc_tbegin (0))

	{

	  if (*lock == 0)

	    return 0;

	  /* Lock was busy.  Fall back to normal locking.  */

	  __libc_tabort (_ABORT_LOCK_BUSY);

	}

      else

	{

	  /* A persistent failure indicates that a retry will probably

	     result in another failure.  Use normal locking now and

	     for the next couple of calls.  */

	  if (_TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ()))

	    {

	      if (aconf.skip_lock_internal_abort > 0)

		atomic_store_relaxed (adapt_count,

				      aconf.skip_lock_internal_abort);

	      goto use_lock;

	    }

	}

     }

  /* Fall back to locks for a bit if retries have been exhausted */

  if (aconf.try_tbegin > 0 && aconf.skip_lock_out_of_tbegin_retries > 0)

    atomic_store_relaxed (adapt_count,

			  aconf.skip_lock_out_of_tbegin_retries);

use_lock:

#endif

  return LLL_LOCK ((*lock), pshared);

}