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/* Copyright (C) 2005, 2008, 2009, 2011 Free Software Foundation, Inc.

   Contributed by Richard Henderson <rth@redhat.com>.

   This file is part of the GNU OpenMP Library (libgomp).

   Libgomp is free software; you can redistribute it and/or modify it

   under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3, or (at your option)

   any later version.

   Libgomp 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 General Public License for

   more details.

   Under Section 7 of GPL version 3, you are granted additional

   permissions described in the GCC Runtime Library Exception, version

   3.1, as published by the Free Software Foundation.

   You should have received a copy of the GNU General Public License and

   a copy of the GCC Runtime Library Exception along with this program;

   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

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

/* This is a Linux specific implementation of the public OpenMP locking

   primitives.  This implementation uses atomic instructions and the futex

   syscall.  */

#include <string.h>

#include <unistd.h>

#include <sys/syscall.h>

#include "wait.h"

/* The internal gomp_mutex_t and the external non-recursive omp_lock_t

   have the same form.  Re-use it.  */

void

gomp_init_lock_30 (omp_lock_t *lock)

{

  gomp_mutex_init (lock);

}

void

gomp_destroy_lock_30 (omp_lock_t *lock)

{

  gomp_mutex_destroy (lock);

}

void

gomp_set_lock_30 (omp_lock_t *lock)

{

  gomp_mutex_lock (lock);

}

void

gomp_unset_lock_30 (omp_lock_t *lock)

{

  gomp_mutex_unlock (lock);

}

int

gomp_test_lock_30 (omp_lock_t *lock)

{

  int oldval = 0;

  return __atomic_compare_exchange_n (lock, &oldval, 1, false,

                                      MEMMODEL_ACQUIRE, MEMMODEL_RELAXED);

}

void

gomp_init_nest_lock_30 (omp_nest_lock_t *lock)

{

  memset (lock, '\0', sizeof (*lock));

}

void

gomp_destroy_nest_lock_30 (omp_nest_lock_t *lock)

{

}

void

gomp_set_nest_lock_30 (omp_nest_lock_t *lock)

{

  void *me = gomp_icv (true);

  if (lock->owner != me)

    {

      gomp_mutex_lock (&lock->lock);

      lock->owner = me;

    }

  lock->count++;

}

void

gomp_unset_nest_lock_30 (omp_nest_lock_t *lock)

{

  if (--lock->count == 0)

    {

      lock->owner = NULL;

      gomp_mutex_unlock (&lock->lock);

    }

}

int

gomp_test_nest_lock_30 (omp_nest_lock_t *lock)

{

  void *me = gomp_icv (true);

  int oldval;

  if (lock->owner == me)

    return ++lock->count;

  oldval = 0;

  if (__atomic_compare_exchange_n (&lock->lock, &oldval, 1, false,

                                   MEMMODEL_ACQUIRE, MEMMODEL_RELAXED))

    {

      lock->owner = me;

      lock->count = 1;

      return 1;

    }

  return 0;

}

#ifdef LIBGOMP_GNU_SYMBOL_VERSIONING

/* gomp_mutex_* can be safely locked in one thread and

   unlocked in another thread, so the OpenMP 2.5 and OpenMP 3.0

   non-nested locks can be the same.  */

strong_alias (gomp_init_lock_30, gomp_init_lock_25)

strong_alias (gomp_destroy_lock_30, gomp_destroy_lock_25)

strong_alias (gomp_set_lock_30, gomp_set_lock_25)

strong_alias (gomp_unset_lock_30, gomp_unset_lock_25)

strong_alias (gomp_test_lock_30, gomp_test_lock_25)

/* The external recursive omp_nest_lock_25_t form requires additional work.  */

/* We need an integer to uniquely identify this thread.  Most generally

   this is the thread's TID, which ideally we'd get this straight from

   the TLS block where glibc keeps it.  Unfortunately, we can't get at

   that directly.

   If we don't support (or have disabled) TLS, one function call is as

   good (or bad) as any other.  Use the syscall all the time.

   On an ILP32 system (defined here as not LP64), we can make do with

   any thread-local pointer.  Ideally we'd use the TLS base address,

   since that requires the least amount of arithmetic, but that's not

   always available directly.  Make do with the gomp_thread pointer

   since it's handy.  */

# if !defined (HAVE_TLS)

static inline int gomp_tid (void)

{

  return syscall (SYS_gettid);

}

# elif !defined(__LP64__)

static inline int gomp_tid (void)

{

  return (int) gomp_thread ();

}

# else

static __thread int tid_cache;

static inline int gomp_tid (void)

{

  int tid = tid_cache;

  if (__builtin_expect (tid == 0, 0))

    tid_cache = tid = syscall (SYS_gettid);

  return tid;

}

# endif

void

gomp_init_nest_lock_25 (omp_nest_lock_25_t *lock)

{

  memset (lock, 0, sizeof (lock));

}

void

gomp_destroy_nest_lock_25 (omp_nest_lock_25_t *lock)

{

}

void

gomp_set_nest_lock_25 (omp_nest_lock_25_t *lock)

{

  int otid, tid = gomp_tid ();

  while (1)

    {

      otid = 0;

      if (__atomic_compare_exchange_n (&lock->owner, &otid, tid, false,

                                       MEMMODEL_ACQUIRE, MEMMODEL_RELAXED))

        {

          lock->count = 1;

          return;

        }

      if (otid == tid)

        {

          lock->count++;

          return;

        }

      do_wait (&lock->owner, otid);

    }

}

void

gomp_unset_nest_lock_25 (omp_nest_lock_25_t *lock)

{

  /* ??? Validate that we own the lock here.  */

  if (--lock->count == 0)

    {

      __atomic_store_n (&lock->owner, 0, MEMMODEL_RELEASE);

      futex_wake (&lock->owner, 1);

    }

}

int

gomp_test_nest_lock_25 (omp_nest_lock_25_t *lock)

{

  int otid, tid = gomp_tid ();

  otid = 0;

  if (__atomic_compare_exchange_n (&lock->owner, &otid, tid, false,

                                   MEMMODEL_ACQUIRE, MEMMODEL_RELAXED))

    {

      lock->count = 1;

      return 1;

    }

  if (otid == tid)

    return ++lock->count;

  return 0;

}

omp_lock_symver (omp_init_lock)

omp_lock_symver (omp_destroy_lock)

omp_lock_symver (omp_set_lock)

omp_lock_symver (omp_unset_lock)

omp_lock_symver (omp_test_lock)

omp_lock_symver (omp_init_nest_lock)

omp_lock_symver (omp_destroy_nest_lock)

omp_lock_symver (omp_set_nest_lock)

omp_lock_symver (omp_unset_nest_lock)

omp_lock_symver (omp_test_nest_lock)

#else

ialias (omp_init_lock)

ialias (omp_init_nest_lock)

ialias (omp_destroy_lock)

ialias (omp_destroy_nest_lock)

ialias (omp_set_lock)

ialias (omp_set_nest_lock)

ialias (omp_unset_lock)

ialias (omp_unset_nest_lock)

ialias (omp_test_lock)

ialias (omp_test_nest_lock)

#endif