/* Copyright (C) 2002-2020 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, see
   <https://www.gnu.org/licenses/>.  */

#include <errno.h>
#include <search.h>
#include <sys/mman.h>
#include "semaphoreP.h"

struct walk_closure
{
  sem_t *the_sem;
  struct inuse_sem *rec;
};

static void
walker (const void *inodep, VISIT which, void *closure0)
{
  struct walk_closure *closure = closure0;
  struct inuse_sem *nodep = *(struct inuse_sem **) inodep;

  if (nodep->sem == closure->the_sem)
    closure->rec = nodep;
}


int
sem_close (sem_t *sem)
{
  int result = 0;

  /* Get the lock.  */
  lll_lock (__sem_mappings_lock, LLL_PRIVATE);

  /* Locate the entry for the mapping the caller provided.  */
  struct inuse_sem *rec;
  {
    struct walk_closure closure = { .the_sem = sem, .rec = NULL };
    __twalk_r (__sem_mappings, walker, &closure);
    rec = closure.rec;
  }
  if  (rec != NULL)
    {
      /* Check the reference counter.  If it is going to be zero, free
	 all the resources.  */
      if (--rec->refcnt == 0)
	{
	  /* Remove the record from the tree.  */
	  (void) __tdelete (rec, &__sem_mappings, __sem_search);

	  result = munmap (rec->sem, sizeof (sem_t));

	  free (rec);
	}
    }
  else
    {
      /* This is no valid semaphore.  */
      result = -1;
      __set_errno (EINVAL);
    }

  /* Release the lock.  */
  lll_unlock (__sem_mappings_lock, LLL_PRIVATE);

  return result;
}